The Mystery of Coffee and Diabetes

Is coffee good or bad for diabetes? Some studies show that coffee is protective, while others say it’s harmful. Some say decaf is better; others say it’s worse. Let’s try to sort this out.


For years, various studies have reported that coffee drinkers are less likely to develop Type 2 diabetes. A recent UCLA study found that “women who drink at least four cups of coffee a day are less than half as likely to develop diabetes as non-coffee drinkers.” Lead scientist Simin Liu said that coffee may improve the body’s tolerance to glucose by increasing metabolism or lowering insulin resistance.

In 2008, Diabetes Self-Management blogger Amy Campbell reported on several other studies showing benefits for coffee. A study published in Diabetes Care in 2006 followed about 900 adults, roughly 300 of whom had prediabetes, for eight years. The people who drank caffeinated coffee had a 60% lower risk of getting diabetes than those who didn’t drink coffee.

Another Diabetes Care study published the same year looked at more than 88,000 women in the Nurses’ Health Study II. It found that women who drank two or more cups of coffee daily had a lower risk (slightly more than half the risk) of getting diabetes than those who drank just one cup of coffee daily, or no coffee at all. And it didn’t matter whether the coffee was regular or decaf.

So right there you have a disagreement about caffeine. Meanwhile, other studies have shown that coffee, or the caffeine in coffee, raises after-meal (postprandial) blood glucose levels up to 20% in people with diabetes. These studies have not been large but have received a lot of attention. In the most-reported study, from Duke University, ten subjects, all with diabetes, were tested — given either caffeine capsules or a placebo (inactive treatment), then switched to the other type of capsules. All showed higher blood glucose levels on the days they took caffeine.

Lead researcher James Lane, PhD, wrote that “In contrast to nondiabetic subjects, our subjects demonstrated exaggerations of both glucose and insulin responses when caffeine was ingested with carbohydrates.”

In a survey on a Mayo Clinic diabetes blog, most readers reported that coffee raised their glucose, even if they had no cream, sugar, or any other food at the time. A reader named Sherri posted, “I drink one large cup in the morning (with flavored cream) before breakfast. [When I monitor], I find that my glucose level is already at high normal for two hours after a meal, and I didn’t even eat yet!”

So how can coffee protect against diabetes if it raises blood sugar? Is coffee good for preventing diabetes, but bad once you already have it? How could this be?

How Coffee Might Protect
First of all, what is going on in people’s bodies when they drink coffee? The UCLA researchers have found that a protein called sex hormone-binding globulin (SHBG) somehow lowers insulin resistance. Most coffee drinkers greatly increased levels of SHBG in the UCLA study. The people with higher SHBG were the ones who didn’t develop diabetes.

A 2009 study in The New England Journal of Medicine of over 800 women found that “higher plasma levels of SHBG were… associated with a lower risk of Type 2 diabetes.” The lowest SHBG group had twenty times the risk for Type 2 of the highest SHBG group.

This is pretty convincing evidence for SHBG, and since coffee is the first way anyone has found to raise SHBG, it might be very helpful stuff. But coffee is a complex substance, with hundreds of natural chemicals in it. How does it work, and what kind of coffee is best?

Is It the Caffeine?
If coffee is good for you, but caffeine is bad, then maybe decaf coffee is the answer? But the UCLA study found that decaf drinkers did not get the protective benefits of coffee. In the two Diabetes Care studies cited by Amy Campbell, one found that decaf or regular worked equally well, while the other found benefits only for caffeinated coffee.

Perhaps the mice have the answer. Reporting in the Journal of Agricultural and Food Chemistry, Fumihiko Horio and colleagues at Nagoya University in Japan fed either water or coffee to a group of laboratory mice engineered to be susceptible to diabetes. According to Science Daily, “Coffee consumption prevented the development of high blood sugar and also improved insulin sensitivity in the mice, thereby reducing the risk of diabetes. Coffee also caused a cascade of other beneficial changes in the…liver and inflammatory [chemicals] related to a reduced diabetes risk. Additional lab studies showed that caffeine may be ‘one of the most effective anti-diabetic compounds in coffee,’ the scientists say.”

So what’s the answer? It certainly seems that coffee protects against Type 2 diabetes, with more evidence for the caffeinated version than for decaf. For people with Type 2 diabetes, going with decaf would be safer, but it’s possible that regular might be more effective. Maybe the temporary glucose spikes, associated with drinking caffeinated coffee with meals, may be worth it in the long run. Or maybe not. People with Type 1 might be better off with decaf. We just don’t know, but with or without caffeine, coffee seems to be one of nature’s wonder drugs for many people. Of course, you should check your own blood glucose levels and see how it affects you personally.

I’d like us to conduct our own study here. Does coffee raise your glucose levels or lower them? What have you noticed about the effects of coffee drinking on your diabetes?

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  • calgarydiabetic

    This is fascinating David.

    Caffeinated coffee will definitely spike my BG at lot so it is hard to see caffeine being a good guy after you have developed D. Before D who knows? My wife who is well on her way to D is Swedish were coffee is a sacred ritual so it does not seam to have helped her. She has a BMI of 22 and has never eaten at American junk food establishments. She eats fairly low carb.

    I am not 100% sure which type I am. I take a lot of insulin and I am very insulin resistant. I could be some sort of slow onset older type 1. Loosing weight and tonnes of exercise did not reverse the D. Avandia did not help. Nobody ever did a proper diagnosis.

    Nevertheless the results above cannot be dismissed and might point the way for effective treatment when the biologists unravel all this and explain it to the Endos.

    Aslo interesting in wiki. was the “transcortin” that binds to cortisol, corticosteroids and progesterone. I don’t know about progesterone but cortisol is very bad for diabetes one of the effects of Cushings is diabetes and corticosteroids are a blood sugar disaster when they are prescribed to diabetics.

    Thanks a lot for the post.

  • a.j. spero

    Fascinating article. How complex it all is.

  • Maria Huff

    I have type 2 diabetes and have just switched from Advandia 4mgs once a day to Metformin500mgs twice a day. I requested the change as taking the Advandia was getting to be stressful due to the bad publicity
    I was reading the other day about C-peptides and how they are not in the synthetic insulin that is given now.. they were in the old animal based insulin..
    As for Coffee . I can not drink the ground stuff that comes in a can..
    I grind my own beans and get along great.. it doesn’t seem to raise my blood sugar .I do limit my coffee to one cup in the morning..Also I can not use half-half in my coffee as my blood sugar is affected by the fat.

  • Annette Prickett

    When I have had a few sips of coffee in the morning BEFORE taking any meds or eating, blood glucose spiks to 116 when it is normally 95

  • Jean

    Interesting article. I have found that since giving up caffeine in coffee, my fasting blood sugar is better. I occasionally will have a drink with caffeine in it, but not often. I’ve also found that giving up diet soda has helped also!

  • Jaci

    I’ve had to convince my endocrinologist that coffee/caffeine does raise my blood sugar. When I do a fasting blood sugar, I’m fine. If I forget to bolus when I have coffee, my blood sugar really spikes. I bolus for the carbs in my half & half and what’s in my artificial sweetener. But I also need to add in some insulin to cover the caffeine.

  • Lawrence Wackerman

    I have type 2 and love coffee: regular in AM and decaf in PM. Thank heaven for this study. I’ll take it as proof that they are both good for me. (My doctor is very happy with how well I am doing.)
    Play it safe and end the studies before you find something bad about coffee!

  • Tim Gimeno

    I have found that with or without coffee sugars were no different. As a younger person I drank a lot of coffee even up to the time I was diagnosed with type 2 at the age of 55. I still feel that stress was the leading factor for me, along with heritage.

  • Rebecca

    My blood sugar levels spike if I drink tea with caffiene as opposed to decaf tea. So It’s not just the coffee!

  • Diane Fadley

    I am a type 1 diabetic and regular coffee definitely raises my blood sugar. I count 1 cup as 5g of carbs and take insulin to cover that.

  • John R.

    I am a 64 year old man. I was diagnosed as a diabetic about 10 years ago after taking a glucose tolerance test. Both of my parents were Type 2 Insulin dependent. I have been able to control my diabetes with exercise and diet alone. I check my fasting glucose levels daily in the morning. It almost always 80 to 90 range. HgA1C is 5.7. I do not know if it has helped, but I drink 4 to 6 cups of decafinated coffee on a daily basis and have done so since 1987 when I suffered a closed head injury and was forced to become decafinated. Prior to that I would drink the same amount (4-6 cups) of coffee with the cafine intact. Although it is not scientificly suported, it is my opnion that coffee has most likely helped to control my glucose levels. Given my family history, I had expected to be medicated for diabetes by now.

  • BimBam

    My mother could not get a foot ulcer to heal after I tried all my “health” tricks.

    I finally told her she must stop drinking coffee, which I suspected for a long time but did not ask her to do so because she loved coffee.

    But, I laid it on the line about amputation. She stopped drinking coffee and the foot ulcer finally began to show signs of healing on or about the 7th day.

    I did nothing else but stop the coffee. So, that is why as a diabetic you should not drink coffee.

    We also stopped drinking tea.

  • BimBam

    My mother who is diabetic could not get a foot ulcer to heal after I tried all my “health” tricks.

    I finally told her she must stop drinking coffee, which I suspected for a long time but did not ask her to do so because she loved coffee.

    But, I laid it on the line about amputation. She stopped drinking coffee and the foot ulcer finally began to show signs of healing on or about the 7th day.

    She is fine now with no other foot problems have occurred since she quit drinking coffee and it has been several years. She had numerous severe foot problems before this last ulcer off and on.

    I did nothing else but stop the coffee. So, that is why as a diabetic you should not drink coffee.

    We also stopped drinking tea.

  • Tabitha

    I found when I was hypoglycemic that caffeine lowered my blood sugar – to the point of a hypoglycemic episode. About an hour after breakfast with coffee, I would start getting hungry, then would go hypoglycemic if I didn’t have something more to eat. When I was diagnosed with diabetes, I thought that would stop — but it didn’t. After 10 years as a diabetic, the same thing still happens — why?

  • Ginger Almy

    This study fascinates me. I have been a Type 1 diabetic for 44 years. Coffee consumption is 2 large cups of coffee each morning with Coffeemate Lite. In the past 3 years, we mix caffeinated and decaf evenly. Even though I compensate the creamer calories/carbs with insulin, I’ve never been able to explain why my blood sugars are so high before lunch. Breakfast, if any, is lite yogurt or a single serving of sugar free applesauce.

    Thank you “calgarydiabetic” for pointing out the possible connection between cortisol producing agents in coffee. That would definitely cause the glucose spike.

    FYI, one cortisone shot will triple my insulin requirement for 3 full days.

  • Dave

    I drink a lot of coffee. Is tea better, if I switched?

  • Maria Huff

    I find that if I don’t eat a little something say at least a slice of whole grain toast with my coffee I get a higher post prandle reading. I seem to need to have some food . I have one latte a day which I make at home with low fat milk. I do not use fat free milk because if you check the sugar content you will discover that fat free dairy contains more sugar than low fat dairy. For some reason food manufactures think they need to either add more sugar or more salt to fat free products. Milk and Dairy are the worst for that .. Also be aware that fat free cheese contains corn starch which breaks down into sugar.
    A good spread for me is to take 1/2 olive oil and one half real butter and whip togeather . Usually I use a little cashew butter on my toast as I have a peanut alergy .

  • Bethany A Brown

    I also have a spike in blood sugar when I drink coffee, either regular or decaf. So whatever is responsible must not be the caffeine. I do not use any sweeteners or liquid coffee creamers, just a couple tablespoons of whole milk in a 16 oz travel cup in the morning. My sugar can spike 30-40 points after having just coffee – no food.

  • Cathy A.

    I drink a lot of coffee. Grind my own beans. It does nothing for my blood sugars, either up or down. It just makes me feel good. On the rare occasion I go to Starbucks and get a latte, though, my sugar goes way up and stays there. Too much extra stuff in it. I will continue to stick with my black coffee. Good article.

  • Barbara Fiedler

    I have been diabetic for about 19 years. I used to drink coffee when I was younger, then went through a period of caffeine free due to tachycardia. A couple of years ago I started drinking coffee again. It has had absolutely no affect on my blood sugar what so ever! I drink two cups a day (as I told my cardiologist :o) ). But they are huge cups!! So make that probably 4 usual size cups. And I use about one level teaspoon in each of the large cups, so 2 teaspoons. And half & half in each cup. All this before breakfast. Then test before I eat and blood sugar is still around 80. No spike at all! What I cannot do without adding insulin, is eat dry cereal!! Absolutely everything these days has way too much sugar and way too much salt added!! So most days I just have oatmeal! I cannot use artificial sweetener of any kind, I get migraines. So I either use regular sugar or honey, both in moderation.

    Thank you for a very interesting article!!

  • Pam D

    I am a type 1 diabetic for 38 yrs. I drink 1 cup of coffee each am with stevia sweetener and half and half. My blood sugar jumps up 30 pts. My CDE told me to take an extra .25 units of insulin just for the coffee. She said she has found that coffee did raise her bg along with alot of other clients.

    Helpful information!

  • Helen

    Coffee is my life blood and I can’t imagine mornings without several cups of the steaming caffeinated stuff. I’ve always drank my coffee black even before my diagnose almost 6 years ago and do not have a significant blood sugar increase.

  • Bob

    My employer provides annual blood tests for $10 so needless to say, I participate each year. Over the years, I saw my blood sugar levels slowly climbing to the point where they fell just above the high level. I read somewhere that coffee could throw off the levels for some tests included in a basic blood workup. For me it didn’t make any sense because I always drink my coffee black with no sugar. I always fasted the night before my tests but would have 1 – 2 cups of coffee in the morning prior to the test thinking it would have no effect. I decided to check out the effects of eliminating my coffee and now for the past 3 years my blood sugar levels have dropped to median levels or below. Looking at some of the comments it looks like it affects some people while others not at all; similar to how different people’s bodies process foods high in cholesterol. Some see huge spikes; others very little. Who knows? =;<)

  • Dan Bennett

    I find my glucose spikes after a cup of coffee. My theory is that I have always been kinda sensitive to caffeine anyway and I think it causes me to react by releasing stress hormones which causes me to spike and if I don’t eat something then I tend to go low after the spike. I am no doctor but it makes sense to me because when I am stressed my bg goes up. Strangely this does not happen with tea. I believe the caffeine in tea is released in the body at a slower rate. I will stick to my tea or decaf coffee.

  • Holly Wirth

    I have found that coffee with caffine in it raises my blood sugar just a touch, but it doesn’t bother if it’s just a touch because I do like my coffee, But if I’m going to drink more than 3 or 4 cups I switch to decaff.

  • Ed Dauksz

    have type 2 and drink decaf coffee. What impact does that have?

  • Joye

    I did a test this morning after reading this, and I could see no difference inblood sugar between before and after having a cup af coffee. However, I had nothing with that cup of coffee, so now this afternoon I’m going to do the test again with some nonsweet carb with it and see if having coffee with a carb influences the carb results. I find all this very interesting and if I do find a difference I will definitely make use of it in my diet.


    everything raises my blood sugar. i mean everything.
    watching tv, going to the bathroom(will raise it 25 points). i used to smoke cigars(quit 2006), the big ones raised it 150-200 points.
    after i eat, it’ll be several hours before the level comes down to under 200.
    my dr. wanted to put me on several different meds.
    but i refused. al of the ones he wanted me on has since been taken off the market, for causing death by heart attact.
    the more medicine i take for high sugar, the higher
    my blood pressure goes. so i end up taking my sugar meds till my blood pressure starts going up, then quit till it comes back down.
    i take glimpiride, and several vitamins for my blood sugar.

  • Henrech Lib

    I am a diabetic (type 2).In my case black coffie lowers the goucose levels in the blood.

  • julia vaughn

    I was diagnosed as a diabetic 8yrs.ago.I control my prediabetes with exercise an diet alone.I just recently increased my coffee because ijust had a taste for some coffee.I checked my blood sugar the next morning an it had dropped 10-12 points.I thought about what i had done different the day before.I drink 3 mugs of coffee with regular an caffine mixed every morning.I had increased 3mugs of decafinated around 4pm.I have done this for four days now.My glucose readings in the morning an at night [before & after meals]are still 89-90 range.I also exercise from 10min.-15-20-minutes twice to three times daily.Moderate speed.I changed my last exercise time to 8pm.So,i don’t know if its the combination of both or if its the coffee.

  • christine

    I have to cover my coffees’ w/ 2 uhumalog and if its w/ cream ck the carbs which is usually 2 but how many tblspn.. so coffeemate sugar free is best.. I am type 1..took a long time to figure this out just a problem when your itching for an ice coffee and didnt calculate Im not on a pump..

  • Sarah

    I am a Type 1 of 37 years. Over the
    last 10 years, I can drink only coffee
    (often 50-50)in the morning and have
    my sugar spike up to 50 points
    especially when I am not being very
    active though sometimes it just spikes
    regardless of activity. However, most
    times it is less than 30 points and
    since I am heading into a walk and
    low-carb breakfast I do not dose.And,
    it doesn’t happen every day.
    Glad you covered this topic.

  • David Spero RN

    Well, it’s still a mystery to me. Most people seem to have some kind of spike with coffee, with or without caffeine, with or without carbs. But some people don’t.

    So how to explain the coffee’s protective effect against Type 2? Is it possible that coffee could raise short-term blood sugar levels but still be good for diabetes in the long term? And would this apply to Type 1 as well?

    Thanks to everyone who has posted. Perhaps we can get to the bottom of this.

  • Pam S

    I am a type II diabetic. My blood sugar will
    spike 50 points after two cups of coffee. Then
    after a little exercise, I will drop very rapidly so that I become hypoglycemic. Coffee really has
    an effect on my blood sugar.

  • jim snell

    As one who has liver issues making too much glucose and shutting doen with metformin; I do not see these issues with spiking and have two cups of regular percolated coffee every morning.

    I am not fan of decaff as the process to remove caffene involves using carbon tetrchloride – dry cleaning fluid to remove the caffiene. That does not impress me consuming residue of carbon tet.

  • jim snell

    one other key issue. Are you drinking coffee black – no canned creme, creme, milk, coffeemate

    Coffeemate because it has corn syrup solids in it and NO sugar; the corn syrup solids do jump the BG.

    Once I drank black – then no noticeable jump.

    Type 2 diabetics – and I am one of those where any hint of sugar, corn syrup solids will jump the BG in early am. Once system up and running not much issue for this person.

  • kathleen Kadron

    when i tested this morning my sugar level was 105 then i had coffee with coffemate and i measured my blood sugar levels at 11am after breakfast and it was 305 can you imagine my shock. i have type 2 diabites, the only other items i had to eat was a bowl of bran flakes and some milk plus mabey 6-8 grapes. thats when i started to investigate coffee mate. i will monitor this for a few days and see if there is any difference without drinking coffe or without drinking coffee with coffeemate.

    • Lorraine

      Grapes are so sugary, everything you ate turns to sugar like bran flakes and milk.

  • Mary

    I am like Steven above that says no matter what he does his blood sugar goes up. I have just recently gone insulin I take Levemir in the mornings and Novalog during my biggest meal my sugar stills runs over 200 and into the 3’s I just dont know what to do. I am fixing to have the lapband surgery done and the nutrition says I have to stop drinking caffeine? I really dont understand why but I am just wondering why caffeine is so bad…I did notice that caffeine coffee did spike my sugar level even though I hadnt eat..So to all this can you give me any type of information so my mind can be at ease and hopefully help me in some way?


    azhar gil from pakistan.i am 44 and diabetese since 10 feeling much better after starting coffee one cup caffinated daily,

  • jim snell

    Here we go again; are we drinking coffee black?

    Coffee mate ia NOT SUGAR FREE as the corn sugar/starches are in the bloody stuff and even the “sugar Free” versions and when I questioned the folks on that – they pointed out the small star on the sugar solids on the label in the sugar free stuff that always spiked me in am. Apparently the FDA lets em get away with this con job.

    If you are drinking black and then claim about spiking BG on coffee drinking may be valid.

  • Carrie

    I recently found out I have pre-diabetes. I have a glucose meter, so I have been monitoring my blood sugar for about a week. This morning my fasting glucose level was 108. For breakfast I had two cups of strong black coffee and 1 oz of cheese which, according to the label, had zero carbohydrates. Two hours later my blood glucose was 118! It went up 10 points after 2 cups of coffe and 1 oz of cheese? How can that be?

    Incidentally, when I say black coffee, I mean absolutely no sweeteners or creamers, just plain coffee.

  • Andrew

    To drink or not to drink (coffee).

    I have been diagnosed type 2 diabetic for 7 years.
    I always drank coffee like there was no tommorrow.
    Coffee definately contributed to my condition.
    I can now only drink the cheap chicory/coffee mixtures as normal coffee makes me feel so ill if I have it for a few days then go back to the cheap stufff.
    Even the coffee/chicory stuff is now affecting me so that will also have to go in place for decaf.

    So I believe coffee contributes to carb cravings, adrenal stimulation and ultimately unstable blood sugar.

    Andrew. southafrica

  • Donna

    After reading meany of these posts, it seems to me that there appears to be a pretty good correlation between drinking coffee (caffeinated or decaf) and folks that exercise and non-exercisers. While we know that diet and exercise are the key to avoiding and/or controlling type 2 diabetes, it is obvious that exercisers do not seen to have as much a problem with the bg spikes from drinking coffee.

    Penny for your thoughts on this….

  • bsmith

    I am an insulin dependent diabetic (insulin pump/novolog last a1c was 5.9) and have been for ~18 years (since I was 13). Years ago I noticed that after a cup of coffee (maybe 8-10 oz, the smaller styro cups in waiting rooms/etc)even though I only used non-dairy creamer (powder) and sweet&low, my glucose levels would reach the 200’s. This always puzzled me and I never even thought about the caffeine. Now, I’m 99% sure that’s the problem either from the caffeine allowing my liver to release glucose or decreased sensitivity to insulin for a short period.

    Now trying to come up with an appropriate bolus in anticipation of coffee consumption, that should be fun! Are we bolusing the amount of coffee, the amount of caffeine, does freshness effect rises, how about temp….?

    Obviously its a person to person case but this is interesting for sure. The conflicting studies do have me puzzled and im not sure where to place my trust.

  • xanthra

    Sing along, “I love the java and the java loves me…”
    I’ve been a type 2 for 3 years. Regular coffee does not raise my blood glucose. I only drink it in the morning. Just reporting in to get a balance. I drink the bold or french roast.

  • jim snell

    Not so fast: For bsmith:

    powered cow and that other stuff contain corn sugar solids that really cause the blood glucose to jump.

    I went through the whole raindance when I was having such a terrible time in am and taking my coffee and watching it jump. Only BLACK only did not cause a jump.

    I even went for the No sugar added coffee whitener proudly displaying NO SUGAR ADDED.

    Ha ha. The afterseeing my BG spike after jumping, I called up those fakirs at coffee mate and was told they added corn sugar/starch solids and not included in their numbers and the FDA said they could simply add tiny asterisk and tiny print documenting that fact outside the no sugar numbers.

    Been to hades and back tracing and walking this crap and I still say if black only maybe an issue forget all other comments.

  • Rozzie

    Wow–just had a conversation as to why my bg jumped from 201 to 326 after coffee mate coffee and splenda with a “splenda drowned” bowl of regular oatmeal. Looked at Spplenda 1 gm of Carbs per pkg (duhh) also 19 gms of carbs in oatmeal. Really though two mugs of coffee (Caffein perked) with two t. of Coffee Mate regular was the likely culprit. Change is needed here!

  • Demi

    I’ve had Type I diabetes for 47 years plus. Coffee never raised by\my bg until a week ago – same coffee, still 12 oz, of coffee, just about every morning. Lately I’ve been changing my infusion sets trying to figure out what was wrong.
    I even cut back to about 6 oz, of coffee – no dice. It’s raised my bg by 100 points. Ouch!

    I figure I’ll bolus for about 60% of iy and see how that works.

    And I’ve recently had severe issues with my gastroparesis – diagnosed 14 years ago.

    Stay tuned – this body is always changing.

  • robert f.

    this is so cool. i have type 1 adult onset. i have for years been fighting control. the last few days i have been closely monitoring my sugars after black coffee. this morning after 7 hour fast i woke to a 139 blood sugar (i know needs to be lower). my point is after 2 8oz. cups of black coffee it went up to 296. that is a 155 rise in a 2 hour period. took insulane to bring it down and only dropped about 20 points in an hour and a half period. but after i stop drinking coffee within a few hours i will crash. decaf her i come. thank you for your artical. it helped.

  • asif


    i have coffee twice day without milk & sugar and my sugar level is normal or below normal it works for diabetes type 2.

  • David Kerr

    I have type 2 diabetis and I have found that drinking coffee raises my blood glucose. I get up @ 5am, drink a cup of coffee and 1 hour later my blood glucose has risen 40 points and I haven’t even had breakfast yet. Go figure?

  • Sandie

    I am non diabetic reactive hypoglycemic. I now drink only decaff .. I used to use a sugar free mocha blended in w/my 1 cup of coffee in the mornings. ( sugar had splenda in it ) yes I reacted..dropped from around 110 to 76 in about an hour. So I stopped for awhile. tried again..this time used 2% milk and mocha. Tested..was again in the low 100s..dropped to the low 80s..but this time I didnt become hypoglycemic.

    I miss my coffee..what I just read on a label was even though the label states there are ” 0 grams ” of sugar..the first ingredient on the label was CORN SYRUP SOLIDS !! people.that’s pure sugar in another how can they list 0 grms of sugar..that caused me to go reactive ! I’m calling them buggers !!

  • Anne

    I have type 2 diabetes. Even though I haven’t checked my bs after coffee, I accidently found that it helps when I have given in to temptation. The other night I ate too many carbs and vision went blurry. Later, although I seldom drink coffee, I had a craving for a cup. Lo and behold, my vision cleared up. I don’t know how scientific this is but I was grateful to the coffee. I took it with stevia adn 2% milk.

  • Alex

    Hi there,

    I am really confused.


  • Patty

    Wait – the woman sited in this article for saying that one cup of coffee raised her glucose levels before she even ate noted she used flavored cream. That flavored cream is 100% oil and sugar. How could people miss that here. OF COURSE that would raise your blood sugar. I think the only reason coffee is even mentioned is the other things put in their coffee.

  • vickie

    I couldn’t figure out how my sugar would jump 50 mg before I would even eat in the morning, after my cup of coffee. I started doing some research on the web and came across your site. So in my case, yes, my coffee is probaly the culprit. Keep up the studies!

  • j.gibson

    HI YAWL!!,I have been reading all the post´s,i am type1 diabetic on solostar lantus and apidra insulin and i also have noticed the elevated sugar levels after my 1st coffee of the day but i am a little naughty (i have around 200ML OF MILK,AROUND 10GRAMS OF CARBS) but even taking into account the ammount of sugar from the milk i have had (on my european measure scale where 5-8 is norm). a blood sugar of 11 or 12 has been measured with just coffee!.Now im no scientist BUT could the actuall process of BOILING be changing the chemical makeup of the coffee?,either taking something away OR creating new bonds between 2 or more of the many chemicals inside it creating nasty chemicals .ALSO when you think about caffine and the effect that a lot of us drink it for (THE BIG WAKE UP!), We are basically using it as a catalyst SOOOOO,IS IT HAVING THE SAME EFFECT ON OUR LIVER ETC ,EG SPEADING UP PRODUCTION OF GLUCOSE?,and this would explain why some people are effected by caffine and some not BECAUSE in some individiuals the caffine ALSO speeds up insulin production and so maintains normal levels??..just a thought….

  • Maria Blair

    I found caffeinated coffee lower my blood pressure.
    It does not raise my blood sugar levels.

  • Bev W

    Thanks everyone for posting. I haven’t kept track of specific numbers and correlations, but in the past several months I have been enjoying a cup of coffee several times a week. Never cared for it before. My blood sugars have also been acting strangely. (High, not responding well to correction boluses) I’ve been a type 1 for over 30 years and on a pump for the l0. I plan to cut out the coffee and see if my bG responds more predictably.

  • John

    I have 2 cups of coffee with light milk and a spoonful of natvia.
    Without exception coffee raises my readings by at least 3+ following the first cup. I am 66, male and type 2 for 15 years.

  • Rolf

    Somebody mentioned that coffee, but not tea, affected his blood sugar. That is interesting. I have recently be researching Acrylamide. Which is a bad chemical that is formed when things are being roasted. Coffee beans are roasted, but not tea leaves. Some coffee has higher Acrylamide levels than others. Apparently, brewed coffee has lower levels than most instant coffees. Maybe that is why some diabetics don’t get raised blood sugar when they drink coffee.

  • Colin

    Maybe coffee is protective and preventive for non-diabetics but may raise BS if you already have diabetes. I dunno….just a guess…

  • Kj

    After consuming a cup of coffee with half and half, my glucose goes up to 116. That’s with nothing else in my stomach in the morning!
    Is this ok?

  • David Spero RN


    I wouldn’t worry about 116. It’s not that high. It could be the half and half that’s raising your number.

  • Lourdes Espinoza

    I have type 2 diabetes. I have proof my levels decrease only when I drink black coffee. If I use creamer, sugar, milk, and so on it does increase. When I have a bad headache I always test my levels, and sure enough it’s high, 180 and higher. As soon as I have a small cup of black coffee it immediately begins to decrease. Within 15 min I drop from 180 to 155 and soon after my headache is also gone. I strongly believe that black coffee does decrease blood sugars and for that reason I will continue to drink it. I have not tested the decaffeinated coffee but do intend to just to test and measure if it drops and by how much.

  • Eva

    I want to believe that caffeinated coffee is safe to drink for diabetics. I am diabetic type 2. I drank coffee for years at each meals. 6 cups a day at each meal. I have to take in other factors that raises my blood sugar. I read pro and cons in drinking coffee. I have retinopathy in both eyes. The one eye I had shot to bring down the swollen. I do not know how regular coffee suppose to regulate blood sugar spikes when my blood sugar is high. I change my diet to help control sugar spikes. I do not add sugar and cream to my coffee. I drink it black. I think it benefit the sugar level in coffee of not adding cream and sugar to it. I do not want to give up in drinking coffee. Another thing is you eat food with your coffee. The food you eat can be the culprit not the coffee you drink with the meals. I do not believe that coffee prevent diabetes. If it did prevent me from diabetes, I would not have diabetes type 2 that spike my sugar now.

  • Cherise

    Really interesting to hear people’s comments and how some people’s blood sugar raises after drinking coffee and for some people it makes no difference.

    I suppose everyone’s body is different and reacts in different ways to food and medicine. I suppose there’s no harm in trying things, who knows it might work for some people.

  • Teresa

    So glad I found this place with you all. I couldn’t figure out why my level would go from 90 to 240 after a couple of hours in the mornings. I drink caffeinated coffee, always have for 30 years. I am a new Type 1 Diabetic , I use pure Stevia for sweetener and very little powdered creamer. I have cut down to 3 reg. size cups and weakened the coffee but still spike about 100 points after those 3 cups within 1-2 hours, which is scary and really throwing off my management of this disease that is so new and frightening to me.
    Tomorrow i will cut the creamer out and see if it helps but for me, my coffee consumption is DEFINITELY raising my sugar levels much TOO HIGH AND TOO FAST. I don’t want to drink decaf, I’ll have to try maybe 1-2 cups with only the pure organic Stevia that has NO hidden sugars.
    This is already so hard and now my beloved coffee is turning into a no-no…I’m so disappointed. Coffee helps me tremendously with my asthma in the mornings when I am congested or tight. the hot liquid AND caffeine gets me breathing well. What a predicament this is.

  • Diabetic/Paleo

    Coffee black or with milk, skim, cream… it matters!

    Imagine taking 2-4 grams of sugar/carbs prior to testing.

  • Barb35

    Just read something about coffee and diabetes. Been a low end diabetic for 3 years, been a HIGH coffee drinker for 40 yrs. Will have to start testing right after coffee. My biggest issue is rapidly dropping sugar (down to 60s) before lunch sometimes within 2 hours of breakfast. I usually have 4-8 cups of coffee in the morning. Drink it black, zero additives. I take lowest dose of metformin at night. Will be interesting to see what happens right after first coffee………

  • TheTruthAsIKnowIt

    Sorry but this is the most useless article i have ever read.

    • BR549

      I agree; just more research-tards trying to justify their morning addiction. Let’s face it, caffeine is a CNS stimulant and raises our five stress hormones. It raises our glucose levels in response to that “perceived” stress and then attempts to correspondingly elevate insulin levels to drive the glucose through the cell walls. If we are exercising, which would normally happen if we were attempting to outrun a predator, then we would be using up that glucose. Sitting in a booth at Starbucks doesn’t exactly qualify, here.

      Coffee no doubt has some beneficial antioxidants, but decreases digestive performance, adds additional stress to existing cognitive disorders, as well as hypertension. Are they worth the risk? Coffee may be a nice thing if we lived in some non-stressed environment high up in the Andes, but it has NO long term place for anyone with diabetes or anyone living under continual stress. Even asthmatics need to be wary that, while it might have some value as an emergency back-up during an asthma attack, on the long term, it also predisposes one to more asthma attacks. It aggravates exzema, psoriasis, IBS, anxiety, depression, bipolar disorder, schizophrenia and sets the stage for dehydration, which impacts all body functions negatively.

      And where is the discussion on Phase I liver performance and caffeine metabolism?

      So, how again does coffee make its way to being a long term win-win? It doesn’t.

      • Cheryl

        I have to agree….Occasionally I will see research that shows coffee is bad but someone else quickly refutes it. I do believe it messes with the pancreas and causes weight gain and pancreas inflammation.

  • sweet relish

    my blood sugar goes up temporarily after drinking coffee. My blood pressure went from 110/80 to 129/90 but leveled back out after while. I think it is the temporary release of stress hormone..very good effects if you go for a morning walk and want the burning of fat to keep going thru the day, but bad if you just sit and watch tv all day and snack.

  • caitlin

    i’ve been a type 1 diabetic for almost 30 years. I’ve been struggling with high blood sugars for quite some time with no improvement. One morning I had an early morning diabetic checkup. my morning sugar was 120. So i decided to eat breakfast after my appointment to keep the good blood sugar (as i’m usually high when they test me at the office). I only had two cups of regular coffee with plain 1/2 & 1/2 (no sugar or sweetener) before my appointment. my sugar 1-1/2 hours later was 300! I didn’t believe it and challenged my doctor on the high sugar. My doctor asked if I drink coffee. I said I do, a lot. Then she told me caffeine can raise your blood sugar if you’re sensitive enough. Amazing. I was diagnosed then I was 8yo, drinking coffee since i was 10 and only last year found out that caffeine can raise your sugar? I wish I knew then, I wouldn’t have started.

  • Jazzy boy

    I am not sure if I am diabetic yet. I am hoping I have pre diabetes. I am on a mission to lose weight and get both blood sugar and blood pressure under control. And I feel i am succeeding.
    My blood pressure started off consistently around 150-160/95-105. I then started dieting and exercising shedding 9.5 kg in 8 weeks, exercising everyday… I have really pushed it. I am 56 years old. Now I get BP readings as low as 121/77.

    Blood Sugar wise started off regularly in high 7s 7.9 mmol. I now have fasting readings of between 4.7 and 5.5 and normal readings of 6.2- 6.5. Not perfect but not far off.

    This brings me onto coffee or caffeine. I love coffee. I drink it black and strong. It definitely spikes my BS, I have readings consistently of 8.0 within 30 minutes of drinking two mugs. 30 minutes later my BS returns to 6.5 or thereabouts.

    So what this tells me is two things.

    1) coffee spikes my BS level by about 20%
    2) I then recover very quickly to a sort of normal level.

    I have conducted these tests many times, I am almost obsessive about analysing this.

    What can we conclude? My feelings are that coffee /caffiene clearly spikes BS, but short term perhaps if the pancreas is working ok. It is down to the individual to assess their requirements and needs.

    I am now monitoring and testing the limits on my pancreas with a view to see how far and quick I can potentially recover from pre-diabetes. I don’t believe I have diabetes, but I could be wrong and I certainly was heading that way 8 weeks ago.

    • Franks N Beans

      Drink it black on a empty stomach. will help release SHBG in your blood to help you. Drinking it with Sugar or Carbs will actually hurt you by keeping the sugar in your blood.

      Hope that helps. Take care.

  • Nathon Gunn

    I don’t have diabetes, but I know almost exactly 4 to 4.5 hours after caffeine consumption I experience a sometimes *drastic* blood sugar crash that was comparable to that which I have seen in people with hypoglycemia. Sends me in a panic, racing for carbs, jittery and agitated. My assumption is that I am having a big blood sugar spike as a result of the caffeine and four hours later *subsequent drop*. This drop is not something I have seen studied or discussed. I think it is significant and am anticipating seeing this as a feature of future studies.

    • Lisa

      Same here, Nathon. In fact, I recently gave up regular, black coffee because of this observed effect. No matter how much I try to tweak my consumption, or what foods I eat/don’t eat, any coffee/its caffeine equivalent seems to be causing this. Blood sugar crashes can be downright scary. … Your assumption gives me food for thought. (No pun intended.)

  • Linda Barnes

    I noticed that my Blood Glucose number goes too high Between morning and the time I eat my first meal. I drink Coffee with caffeine One or two cups each day with Organic Creamer (11 carbs). I am thinking about changing to Decaf. and see the results. Hoping for a more steady BG as My Morning and Night BG is 80-130<<which is normal. My fasting BG used to be too high, as my BG went up during the night. As Suggested I eat one half a slice of Aunt Milles Best Whole Grains with two teaspoons of peanutbutter before bedtime and now my morning BG is 120-130< which is NORMAL.

    • Russ Miller

      Instead of peanut butter, try almond butter. Almonds are high in magnesium, and great for diabetics. My wife makes it herself. She buys raw almonds in bulk from Winco, roasts them at 350F for 15 min. (2 cups) them runs them through her food processor until the desired consistency(patience is key here). Add salt to taste, and for added flavor, a teaspoon of cinnamon, which is also beneficial for diabetics. Like natural peanut butter, it should be refrigerated. Hope this helps.

  • JP

    Type 2. Wake at 5:00 am with 90 to 100 readings. Drink 3 cups of coffee and readings spike to 200 plus in less than 1 hour. Black, artificial sweetener or with cream all have same result. Something in the coffee is driving the readings.

  • Mukesh Kumar Bidani

    Caffine inhibit phosphodiesterase which breaks phosphodiester bond, a chemical bond of the kind joining successive sugar molecules in a polynucleotide thus it turns off the breaking down of glycogen. Since glycogen doesn’t break into glucose due to caffine, it rises the blood glucose level and stores glucose in the body.

    I can conclude that caffine inhibits glycogenolysis which is break down of stored glycogen into glucose and will lead to hyperglycemia as the upcoming glucose intake will be excess to the body after caffine intake.

    • Ibn Adam

      Caffeine raises cortisol levels which increases the production of glucose in the liver which in turn raises blood glucose. Perhaps this is of the ways glucose increase after taking a cup of coffee. This wouldn’t be a problem for people who are not as sensitive to the increase in cortisol or who have very low cortisol in the morning.

  • LilRedVW

    Since so many people drink coffee first thing in the morning, could the rise in blood sugar numbers be from the Dawn Phenomenon and not from the coffee? I am Type 1, and I just started drinking the occasional cup of coffee. I have a tendency to eat a late breakfast. My blood sugar goes up quite a bit after I get up in the morning before I have breakfast or coffee. For example, the other morning at 5am, it was 111, but by the time I had breakfast at 10:30, it had gone up to 212. I didn’t eat or drink anything. I do take my long acting insulin in the morning, so part of that could be the wear off from the prior day’s shot. It could have to do with what I ate the night before, or maybe it is the Dawn Phenomenon. It’s different for everyone. My bolus with breakfast typically brings me back to a normal range. I can’t tell a difference in my numbers with or without coffee.

  • Jackie R

    I drank decaf for years while diabetic, but the formaldhyde turned me off. It took years to get my a1c down to 6.10 and around the same time we changed my insulin from Lantus to Toujeo I also went to reg caffenated coffee. Now my blood sugar is up to 7.4 I don’t know if it was the Toujeo or the coffee that shot it up. I am back on Lantus but drink the same amount of coffee as before though the caffenated. I really DON’T want to give up my coffee

    • Russ Miller

      I drink naturally decaf’d green tea. They use carbon dioxide to remove the “lead”. I wonder if naturally decaf’d coffee can be had?

  • mikey

    My mother was diagnosed with gestational diabetes which stayed with her the rest of her life, but she was diet-controlled only and, oddly, could sometimes pass a glucose tolerance test; her father, also a type-2 diabetic, was also entirely diet-controlled and often “cheated” (especially ice cream) with no side effects. My parents were both British and stereotypically heavy tea drinkers (black tea), so I consumed tea from a very early age. I also rarely drank coffee until my 20’s; from my 20’s to 30’s I drank both; I put little to no sugar in my tea, and one teaspoon in coffee. Though not a diabetic I struggled with blood sugar issues much of my life; this lessened in my 30’s and I (and my doctor) ascribed my increasing blood sugar stability to increasing body fat, which I’d had little of previously. I never made a connection to tea or coffee, however. But in my mid-30’s one day my fiancee remarked “it seems to me when you have a blood sugar crash, it’s always after you’ve had tea, and you never have one on a morning you’ve had coffee.” I experimented over a couple of weeks and found an association, so pretty much eliminated tea from my diet and have one cup, occasionally two, of coffee per day. For the past 20 years, my blood sugar has remained stable, and previously frequent migraines also dropped to almost never (though I made other lifestyle changes with regards to migraines). Often I have a crash after drinking black tea, however.

  • John Carter


  • Russ Miller

    Once I was diagnosed with type 2 diabetes, I found that coffee(leaded) countered any benefit my glipizide gave me. BTW, I learned that the statin drugs the VA gave me actually caused my diabetes. Since then, I went with a low-fat, low-carb, high-fiber diet, and certain supplements, and was able to wean myself off all drugs, except for the glipizide…so far. The key is to lower insulin resistance. It can be done, but a challenge.

  • Guest

    Type 2 Diabetic for about 18+ years now, became insulin dependent about 15 years ago. Regular coffee (with or without sweeteners, sugar or non-sugar does not matter either way) absolutely crashes down by blood sugar 100 points sometimes, it is the absolute opposite of caffeinated soft-drinks which BOOST blood sugar (huge) always.

  • Cheryl Anderson

    My husband and I drink decaffeinated coffee. We use Coffeemate original powder. Our coffee raises blood sugars about 45 points. The creamer has no carbs, so we can’t figure it out.

    • Harold Simmons

      the creamer is a fat based product. even there are no carbs there is still fat


      Ugh. Coffeemate is poison. Seriously. You are better off with coconut milk, or learn to like black coffee. (High quality black coffee is actually delicious ! … I’m not talking about Maxwell House, Folgers, or any store brand) … Even adding sugar is toxic. Dairy + non-dairy powdered creamers and sugar, negate any health benefits from drinking coffee..

      • Cheryl

        So really why drink coffee if it has to be black. That’s my opinion of course, because I know some people who can drink it black but most people I know have to have sugar and cream. I liked cream til I developed a dairy allergy, so then tried cremora as a last resort and now I’m inflamed, as in arthritis pain and inflamed gums and I’ve gained 20 lbs!

    • SarahMorrow

      One packet of coffee mate has almost two grams of carbs. And it’s almost half sugar! Some people put in two or three packets, then wonder why it affects their blood sugar. As an experiment, try drinking black coffee without it a few times, and see how your numbers change.


    I notice that when I drink coffee with milk or any dairy-type products, my blood sugar goes crazy, and I get binge-eating hungry later in the day, if I’m not careful about what I eat in the meantime. Black coffee never does that to me.

  • I have inherited Type II. Any good Diabetes scientist will tell you that there is more than one type of D2, just as there is not one type of Osteoarthritis or Cancer. Some say there are as many subtle differences of D2’s as there are people with D2. Logic demands that we recognize there is not one simple answer.

    With that said, I will say, with the help of my doctors in Greenville, SC, and UNCMed in Chapel Hill, at the age of 70, I look and feel like a chubby 50-something. I take, daily Toujeo 75units, Jardiance 10mg, MetforminXR 1000mg, and Humalog Pen units/prn. I also take Bumetanide 1mg/d with K CL-XR 50mg Tab. My blood, even as a child was always between 100-200. These days, it’s 70-250. My veins are very large (if that matters to anyone). A1C has always varied between 7-8, depending on the ambient temperature(!). My only gripe is that I micturate every two hours – like clockwork, but it is a small price to pay – very small.

    I drink 30oz of Jamaican Blue coffee with 2T of LOCAL honey & ⅓C Splenda & 2T heavy cream, in the morning, daily – no breakfast. I have discovered that, for me, the coffee,Toujeo, Jardiance, Metformin, & Potassium, suppress my hunger and cravings all day. I have lost 40lbs in 2 years and I’m still losing.

    Just remember, this may NOT work for anybody else. I DOES work for me.

  • David007

    I have tried everything mentioned in this article as well as the comments below. None of it worked. I will still wake up with BG around 190 every day. Then I decided to start an hour a day of intense exercise. I now wake up with a number never higher than 115. I did NOT improve my diet, I just exercised. All of the medicines are BS (metformin at max dose never did a THING for me), and all of the diets only help a little. You will NEVER get to normal numbers unless you do a MINIMUM of 30 minutes a day at a pace that causes significant sweating. Sweating is the key indicator that your exercise is activating thermogenesis

  • Barb Petr

    T1 here….coffee with 1/2 T of heavy cream and 1 Splenda raises my BS by 40 to 50 points. I used to drink quite a few cups a day with no effect…but now, I drink 1 in the morning (caffeine) and none until dinner (decaf) both–caf and decaf raise me 40 to 50 points—I even tried black coffee…but that does the same thing…

  • mitchell_james_kaplan

    Hi. I know this is an old post but I’m very curious. How did that supervised fast work out for you? Did it affect your diabetes, long-term? Thanks.

  • MatBastardson

    Drinking black coffee has been shown to raise blood sugar. Caffeine does this by
    enhancing the effect of two hormones (adrenaline and glucagon). These
    two hormones release stored sugar from the liver resulting in high blood

    Not all diabetics experience this, so the fact that black coffee doesn’t spike your blood sugar doesn’t mean everybody else must be using milk, or creamers, or sugar or other sweeteners in their coffee. When I was first diagnosed (Type II), I was told at the diabetic education seminar that black coffee was okay because it was sugar free, and when I later told my doctor that black coffee seemed to spike my sugar, she said she didn’t think so. Clearly, even some medical professionals are unaware of this phenomenon.

    Even on the internet, I had to do a lot of digging to find this information. My first page of search results pointed to articles and discussions up to 7 years old (like this one) so I’m going ahead and posting here even though it’s currently 2018, just in case you have come looking.

    I don’t know why this information is so hard to find. Maybe it wasn’t known 15 yrs ago when I was first diagnosed and then told by the dietician that coffee, being carb free, was totally safe for me to drink, but the fact is that some people, like me, can see their BG spike drastically after a large mug of black coffee.

    You have to monitor you blood sugar to see if coffee affects you, how high the spike is, and how long it lasts. For me, my coffee does create a pretty large spike, but it’s of pretty short duration.

    • Danyiel Romo Mendoza

      Thanks. I will spread the word.