Metformin and Risk For Vitamin B12 Deficiency

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Dec 04, 2006

Metformin and Risk For Vitamin B12 Deficiency

Amy Campbell

Metformin (brand names Glucophage, Glucophage XR, Fortamet, Riomet, Glumetza, and others) is a popular and highly effective oral diabetes drug used to help manage Type 2 diabetes. This drug works by lowering the amount of glucose made by the liver and by making the body’s cells more sensitive to insulin. Metformin also has some other beneficial effects in that it may help lower blood lipid, or fat, levels (cholesterol and triglycerides) and can, in some people, promote a small amount of weight loss.

Metformin can be used with other diabetes pills and with insulin. Side effects of taking metformin are relatively rare, the most common being bloating, nausea, and diarrhea, all of which are temporary. Some people shouldn't take metformin, including people with kidney disease, liver disease, or congestive heart failure, for example, because of an increased risk of a potentially fatal condition called lactic acidosis.

In recent years, there's been some concern over the risk of vitamin B12 deficiency in people who take metformin. Vitamin B12 (also known as cyanocobalamin or cobalamin) plays many important roles in the body, such as keeping your blood cells and nervous system in tip top shape. There's also some evidence that vitamin B12 may help prevent heart disease and possibly even Alzheimer disease (the jury is still out on this one). This vitamin is found primarily in animal foods, such as beef, seafood, eggs, and dairy products, which is why some vegetarians are at risk for a B12 deficiency. Elderly people are often at risk for deficiency as well, due to problems with absorption from the gastrointestinal tract. Symptoms of B12 deficiency include certain types of anemia, neuropathy, memory loss, confusion, and even dementia.

So, why would taking metformin possibly put you at risk for a B12 deficiency? According to some studies, between 10% and 30% of people who take metformin on a regular basis have some evidence of decreased B12 absorption. Researchers aren't quite sure why this happens. In a study recently published in the October 9 issue of the journal Archives of Internal Medicine,155 Chinese people with Type 2 diabetes taking metformin were identified as having a B12 deficiency, regardless of factors such as age or body weight. The study found that the longer a person had been taking metformin and the higher his daily dose of the drug, the greater his risk of developing B12 deficiency.

The authors of the study advocate consideration of vitamin B12 deficiency screening for people who take metformin. While this screening isn't routine, it's worth it to have a talk with your health-care provider to see if you're at risk for deficiency, especially if you've been taking metformin for several years or take a high dose. Also, if you have any of the symptoms of B12 deficiency mentioned above, particularly those related to neuropathy (numbness, pain, or tingling in your hands or feet), be sure to let your physician know. He or she can check the level of vitamin B12 in your blood.

Vitamin B12 deficiency can be treated with either oral, injected, or inhaled forms of B12. Some people, such as strict vegetarians or the elderly, may need to take supplements or receive injections on a regular basis. B12 is found in most multivitamin supplements, so it doesn't hurt to take a multivitamin as a safeguard. However, avoid taking a B12 supplement unless your doctor has prescribed them. Too much vitamin B12 may be harmful, and B12 can also interact with certain medicines. Always let your health-care team know about all medicines and supplements that you're taking at each visit.

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I m using Vitamin b12Patch to overcome the lack of energy. I was experiencing Fatigue and was feeling stressed out. So I started using this patch. It is required to apply on specified body part. Not required to be injected into the body.

Posted by: Gabriel | Feb 07, 2007 12:56 PM

You can not take to much B12. Its water soluable and any extra is eliminated by your kidneys through urination.

Posted by: Carla | Oct 28, 2007 01:43 AM

Carla,

It's true that vitamin B12 is relatively harmless, as it is a water-soluble vitamin. However, there have been a very small handful of studies linking B12 excess with prostate cancer. B12 injections can cause allergic reactions and mild diarrhea in a small number of people. Taking large doses of B12 along with vitamin C may lead to nosebleeds. The point is that taking large doses of this or any other vitamin, mineral or supplement probably isn't a good without medical supervision.

Posted by: acampbell | Oct 29, 2007 02:48 PM

What information has Bristol Myers Squibb provided to physicians on this matter, if any. Are they taking any efforts to proactively getting this information into the hands of us who take this drug?

Also, I have read that normal tests for B12 levels may not disclose that patients are deficient in B12 as it does not disclose that the problem may be malabsorption.

Are there any studies that indicate Metformin decreases the bodies ability to properly utilize B12 even if it is at adequate levels? Sort of like being insulin resistant except being B12 resistant.

Finally, is Bristol Myers making any proactive attempt to have physicians test specifically for B12 in patient with a long history of metformin use?

Posted by: sh10492 | Jan 06, 2008 10:01 PM

Hi sh10492,

I'm not aware of any particular campaign on the part of Bristol Myers to inform physicians on the potential risk of B12 deficiency with metformin use. However, there is mention of this risk in the package insert for Glucophage/Glucophage XR, and it's recommended in the PI that those at risk for deficiency be screened at 2-3 year intervals. Apparently testing for methylmalonic acid (MMA)over blood B12 levels is recommended by some, but it's use is still somewhat controversial in the medical community. One theory is that metformin may interfere with B12 absorption; however, it appears that supplementation with 1000-1200 mg of calcium can limit this interference with B12 absorption. As I mentioned in my posting, it's important for anyone taking metformin, particularly long-term, to talk to his or her healthcare provider about the potential risk for B12 deficiency and the steps one can take to prevent this from happening.

Posted by: acampbell | Jan 09, 2008 09:11 AM

Thank you for the commenting on my questions.

I find the package insert to be insufficient. It indicates that paitients should be "predisposed" and testing "may be useful".

Given the rates of 30% B12 deficiency it would seem (from a layman's point of view) that taking the medication predisposes one to the deficiency and knowledge of the deficiency would be MORE than useful.

Posted by: sh10492 | Jan 09, 2008 01:57 PM

I was just wondering if it is harmful to take a vitamin B-12 plus prenatal vitamins daily. I am not pregnant, I just thought it would be good to take the prenatal vitamin for the extra vitamins.

Posted by: msmith | Jan 10, 2008 08:51 PM

Hi msmith,

There's very little risk in taking a B-12 supplement. However, I'm wondering why you're taking a prenatal vitamin, given that you're not pregnant. Prenatal vitamins contain more folic acid, iron and calcium than regular multivitamins. Unless it's been advised by your physician, I'd suggest switching to a regular multivitamin and focus on getting the remainder of your vitamins and minerals from food sources.

Posted by: acampbell | Jan 15, 2008 04:17 PM

I have now been taking Vitamin B12 for 24 days. In that time my insulin requirement has gone from 60-65 units to 15-20 daily. I still take Metformin and now take 2000mcg of B12.

My energy level has skyrocketed.It seems my mental cognition and memory have also improved.

Unfortunately many of the symptoms of B12 depletion mimic diabetes complications. I have been suffering from this depletion for at least 4 years and just learned to cope until I hit a wall and suffered many health consequences. It got so bad that in December I had decided to claim my disability insurance as I had no hope of maintaining a 40 hour work week.

Four days after taking Vitamin B12 I began to feel better. Within a week I felt "Good" for the first time in months.

Lets get the word out about this! Too many people are suffering and the drug companies have done nothing to alert patients and physicians of consequences of metformin and glucophage for long term users.

Posted by: sh10492 | Jan 30, 2008 09:39 PM

Hi sh10492,
Thanks for sharing this - very encouraging! Hopefully this will encourage people who take metformin to have a discussion with their provider about a possible risk of B12 depletion.

Posted by: acampbell | Jan 31, 2008 03:16 PM

I have diabetes type two but was not diagnosed long after it should have been
i can not eat because i do not digest food
and so i thought if i could take B-12 Sublin
gual which would go under the tongue and dis
dissolve and quickly enters the blood-stream.

Posted by: C.J.COOK | Feb 29, 2008 04:41 PM

Hi C.J.,
You can certainly take B12 sublingually. You may want to check with your physician as to what dose would be approriate for you. For people who haven't had a source of B12 for a while, a starting dose might be 2000 micrograms daily for a couple of weeks, for example, then tapering down to once a week. For people with deficiencies or other medical issues, B12 injections might be needed. So talk with your physician as to what method and dose would be best for you.

Posted by: acampbell | Mar 03, 2008 01:40 PM

HI ,,,,
CAN I TAKE VITAMIN B6 AND B12 BOTH OF THEM TOGETHER ON THE SAME TIME ,..........
IF SAFE IF I TAKE 200 MLG OF B6, AND
2000 MCG OF B12...
WHAT is the right dose......

CAN I TAKE B6 AND B12 IF I AM TAKING FUROSEMIDE 20 MG ONCE A DAY ,
PLEASE IF SOMEBODY CAN HELP ME...
THANK YOU

Posted by: YL | Apr 01, 2008 12:46 PM

Hi YL,
You can take B6 and B12 together. Also, furosemide may slightly deplete these two vitamins, so it's okay to take them with this medication. You may want to take your vitamins with or after a meal. However, you're taking fairly high doses of B6; the RDA is 1.3-1.5 mg for women, and the upper limit is 100 mg/day. Too much B6 can be harmful. Also, unless you're deficient or have a malabsorption disorder, you don't need 2000 mcg of B12 (anywhere from 1-25 mcg would be okay). I'd suggest you talk with your physician about doses that are best for you.

Posted by: acampbell | Apr 01, 2008 01:46 PM

thank you so much for you advice....
you really gave me a peace of mind....

Posted by: YL | Apr 02, 2008 01:04 PM

This is such an interesting discussion. I was diagnosed with Pernicious anemia as my B12 levels were very low. My Mother and her six sisters also had pernicous anemia as does my older (and only) sister. I am having a b12 injection monthly, but I really feel I need it three weekly as the last week I am so lethargic I can barely move. I have type 2 diabetes and am taking 2000 mg of Metformin daily. I had never heard of the link between the two.

Posted by: Karen | Apr 05, 2008 12:16 AM

Hi, I took Metformin in 2005 and stopped taking it after 18 months without telling my physician, I was prescribed to take a total of 2500mg/day for my PCOS, that's 1000mg at breakfast, 500mg at lunch and 100mg at dinner. I was advised by my physician to take it on a gradually increasing dose which I did. The reason why I stopped taking it was due to being sick of urgently needing to go the toilet every after meal and it's always been loose. After reading your blog, I realised that I may be lacking in B12 when I was taking Metformin as I also get fatigued easily and I became forgetful. The last time I took Metformin was 2 years ago. Now that I just saw another physician, he advised me to start taking Metformin again as it will help my PCOS, but this time, I was only prescribed to take 500mg three times a day. The next time I see my physician I will ask him to check my B12 levels.

Posted by: HoneyNZ | Apr 06, 2008 09:27 PM

I have started getting White hair rapidly. I surfed the web and got the info that its most likely due the deficicency of Vitamin B12. 1). Can you kindly discuss this please? No matter how brief your kind suggestions are. 2). Are vitamin B12 tablets are under non-subscription drugs? i mean should i need to have Doctor's letter to buy these pills? 3). which one is the best product for these pills? Will highly appreciate for your kind suggestions. Thanks!

Posted by: kashif | May 17, 2008 05:34 PM

Hi kashif,
I'm not a hair expert, but please keep in mind that there are many causes of white or graying hair, including family history, age, gender and illness. Pernicious anemia, resulting from a lack of vitamin B12, may also be a cause. However, you should discuss this possibility with your physician before concluding that you're deficient in B12 and before you start taking B12 supplements. B12 is available without a doctor's prescription, but, again, please discuss your concerns with your physician to rule out other possible causes of your white hair.

Posted by: acampbell | May 19, 2008 10:07 AM

I was on Metformin a few years ago and had to stop...after 3 months, I was still vomiting and having horrid bowel movements. My doctor retested me and stated that my previous doctor (the one that prescribed it) might have been over cautious as I had no sign of high blood sugar or triglycerides. However, because of PCOS they recommend that I might want to start taking it again as I am trying to conceive. What do you think? Can and should I take this while taking the prenatal vitamins? I worry about the constant nausea I had previously.

Posted by: tenorsaxgyrl | Jul 02, 2008 11:38 PM

Hi tenorsaxgyrl,
Gastrointestinal side effects occur in up to 1/3 of people who take metformin. Given your previous side effects with this drug, you should talk to your provider about ways that you might prevent them from occuring again, or at least minimize them. Some suggestions are to start with a very low dose and gradually build up; take your metformin with meals; and limit rich, fatty meals. I'm not aware of metformin interacting with prenatal vitamins. You can always try metformin again and see what happens. Obviously, if you still get extreme side effects such as nausea, vomiting and diarrhea, metformin probably isn't for you.

Posted by: acampbell | Jul 03, 2008 11:34 AM

when they check for the b12 deficiency do they do a CBC or a specific B12 test?

Posted by: live4fitness | Jul 23, 2008 03:48 PM

Hi live4fitness,

Vitamin B12 levels are measured, often along with folate (another B vitamin) as a separate blood test. A CBC, or complete blood count, may indicate the presence of large red blood cells, which would then prompt your provider to order a separate B12 blood test.

Posted by: acampbell | Jul 24, 2008 08:21 AM

I took metformin for about a year and it also gave me constant diarrhea. Because of the diarrhea my sodium and magnesium are low and haven't been able to correct the levels yet. I also have a B-12 deficiency, i have been taking shots for almost a year and still my levels are low. My doctor recently said that was enough of the metformin because it seem to do more harm than good, she now has me on a diabetes med called januvia. I have been on this medication for about 3 wks and I haven't had has much diarrhea. I wondered if the diarrhea from the metformin is what caused my B-12 to be low also.

Posted by: superwoman | Jul 27, 2008 09:37 PM

WHEN TAKİNG METFORMİN AND B1 VİT TOGATHER does it
RESULTS İN HAVİNG LACTİC ASSİDOS.

THANK YOU FOR YOUR HELP İN ADVANCE.

FAY SEBENE/Mr.

Posted by: FAY SEBENE. | Jul 28, 2008 08:15 AM

Hi Fay,
No, taking metformin with vitamin B1, which is thiamine, does not cause lactic acidosis. Lactic acidosis is a very serious condition whereby lactic acid builds up in the blood. Symptoms include loss of appetite, nausea, vomiting and abdominal pain. It most often occurs in people with kidney or liver disease, or in people who have tests involving injected dyes, or after surgery. If you take metformin and are scheduled for any kind of radiologic test or surgery, you may need to temporarily stop taking your metformin, so check with your physician for instructions.

Posted by: acampbell | Jul 29, 2008 08:12 AM

Hi superwoman,
It's possible that the diarrhea you've had caused a B12 deficiency; however, it's probably more likely that the metformin itself was responsible. Fortunately, your diarrhea has resolved and hopefully your B12 levels will return to normal soon.

Posted by: acampbell | Jul 29, 2008 08:44 AM

i was recently diagnosed with pcos and am taking metformin (850x daily) along with synthroid for low thyroid. We hope to try to have kids in the next year or so and I have been taking pre-natal vitamins. I saw your previous post about them, should I not be taking them with metformin and synthroid?

Posted by: meridith | Aug 21, 2008 03:09 PM

Hi Meridith,
You might try taking your prenatal vitamins separately from your metformin. Also, it's probably a good idea not to take your vitamins with your Synthroid, as the iron may decrease the absorption and action of your thyroid hormone.

Posted by: acampbell | Aug 22, 2008 03:40 PM

I just turned 35 and in the past year have been having multiple issues including muscle tenderness/tingling, lack of focus, inabilty to sleep the night and light headedness. I may have had these issue in the past off and on, but recently I have been more focused on them as I get older. My sister told me I may be B12 deficient, since we are both Type A+/O+ blood type. Her doctor told her that this combination traditionally is deficient in B12. Does this make sense or is it a possibility?

Posted by: MG | Aug 29, 2008 01:11 PM

I am 72 years old and am a type 2 diabetic. For 5 years I have been taking Metformin 500 x 3 times per day. Tingling/numbness in my feet, pains in legs and ankles also swelling (possible odema) weight gain and general tiredness when walking and I have made an appointment with my GP to discuss these problems re possibility of a B12 deficiency. Apart from my age, would you agree these symptoms could be linked to this type of deficiency? Any comments would be so appreciated. Thank You.

Posted by: Jillybean | Aug 29, 2008 03:48 PM

Hi Jillybean,

Please realize that I'm not a physician and cannot diagnose anyone. However, some of your symptoms could be consistent with a B12 deficiency, including the tingling and numbness in your legs, and your fatigue. Weight gain and swelling are usually not linked with a B12 deficiency. I'm glad to hear that you're going to discuss your symptoms and possible causes with your physician.

Posted by: acampbell | Aug 31, 2008 05:33 PM

Hi MG,
I'm not aware of a particular blood type being linked to B12 deficiency, but I suppose that could be a possibility. The more common causes of B12 deficiency include insufficient intake, malabsorption disorders, such as Crohn's disease, certain types of abdominal surgery, parasites, pernicious anemia and aging. You really should discuss your symptoms with your physician to rule out other possible causes for your symptoms.

Posted by: acampbell | Aug 31, 2008 05:43 PM

I have been experiencing Menieres symptoms for the last five years. In the past two years, I have noticed a rapid progression of vertigo, ataxia, a feeling of falling, and positional problems. Two days ago I started taking a protein powder and vitamin supplement and yesterday I had the first vertigo free day in years. I began to wonder if I might have a vitamin deficiency, and this morning have discovered a possible link between my metformin, vitamin b12 deficiency, and ataxia. I may be grasping for straws, but do you think that there might be a connection?

Thanks
Rose

Posted by: rosdonald | Sep 04, 2008 08:34 AM

Hi Rose,
Not being an expert in Meniere's, I'm a little skeptical that the improvement in your symptoms is due to the vitamin and protein supplements that you've started, particularly after being on both for such a short time. I'm not aware of specific vitamins that have been linked with Meniere's. But, if you've been on metformin for a while, it's possible that you're deficient in B12. Ask your provider at your next appointment to check your B12 level. Also, I'd suggest you go easy with the protein powder; most people don't need additional protein, unless they are ill, have undergone surgery, or follow a strict eating regimen that might restrict protein.

Posted by: acampbell | Sep 05, 2008 11:59 AM

Thank you so much for your response, just to clarify....does that mean I should not take prenatal vitamins at all with metformin and synthroid or just that I should space it out and take the vitamins at a different time in the day than when I take my meds?

Posted by: meridith | Sep 11, 2008 09:52 AM

Hi meridith,

I'd recommend you take your vitamins at a separate time from your medications. It's fine for you to continue with your vitamins AND your meds - just take them apart from each other.

Posted by: acampbell | Sep 11, 2008 02:51 PM

Thank you so much for this discussion! I was wondering if the metformin/B12 deficiency link was as strong when taking Janumet? I have not been tested for B12 deficiency (but plan on discussing that with my doctor soon) but have been suffering from nausea and lightheadedness for the past week. I've been on 50-1,000 mg of Janumet twice a day for 2 months now, and was on metformin for 1 month before that. Also, I had my son 5 months ago and I'm not sure if that's even a factor, if my body is not quite back to normal yet.

Posted by: libelula | Sep 25, 2008 07:09 PM

Hi libelula,
It's certainly possibly that a B12 deficiency could occur when taking Janumet (a combination of Januvia and metformin), although you haven't been taking it for all that long, so a deficiency is probably unlikely at this point. Your nausea could be due to the metformin. Please contact your physician soon to discuss your symptoms and possible causes.

Posted by: acampbell | Sep 28, 2008 12:33 PM

I'm 55 yo & have been taking Metformin for almost 10 yrs. I've often complained to Drs. about leg pain & feeling exhausted. She tested thyroid - it was ok. Now test came back with low iron & B12. I read about the link to Metformin & asked. She said she hasn't seen it clinically. Wants colonoscopy to check for internal bleeding. Why won't Drs. listen to patients?

Posted by: Dorothy | Oct 17, 2008 04:12 PM

Hi Dorothy,
Doctors have so much information to keep up with and stay on top of, and it's very likely that your doctor wasn't aware of the link between metformin and vitamin B12. She's being thorough, though, in ordering a colonoscopy for you. What's often helpful for communicating effectively with healthcare professionals about a particular issue is to bring in a copy of an article that explains the issue; that way, they can do their own "research" (even though it's frustrating when they didn't listen to you in the first place!).

Posted by: acampbell | Oct 18, 2008 04:51 PM

Question - i have seen some information that says taking calcium can reverse the b12 absorbtion issue caused by metformin. have you heard that? is there a recommended dose of calcium, or should i check with my doc. thanks. i got my first b12 shot today for b12, anemia issues. i have taken metformin for 10 years.

Posted by: bertk523 | Nov 19, 2008 12:36 PM

Hi bertk523,

There is some evidence that taking 1200 mg of calcium (as a supplement) may help limit the effect of metformin on B12 levels. It's something you could consider trying, although it's not a bad idea to discuss with your physician, first.

Posted by: acampbell | Nov 20, 2008 08:09 AM

I've been taking Metformin for 10 years. My current dosage is 1000 mg 2x per day. (the max) About 3 months ago I was diagnosed with a B12 deficiency. It must have been very low, because I had to get a shot once a week for a month, then 1 a month since. I told my physician about the study linking metformin with B12 deficiency and she had never heard of it. I asked about changing to a different med, but I was told that we've tried everything else but Insulin. I dont want to go that route unless really necessary If I continue to take the Metformin and the shots will my B12 go back to normal?

Posted by: Joanna | Nov 20, 2008 06:56 PM

Hi Joanna,
Depending on the extent of your B12 deficiency, it probably will take at least several weeks or even a couple of months to restore your levels. You need to keep on top of your levels until they return back to normal. Ask your physician to periodically check your B12 levels after that, as well. In the meantime, make sure that your diet contains plenty of B12 (taking a multivitamin is a good idea if you're not already doing so).

Posted by: acampbell | Nov 24, 2008 08:24 AM

Hi, I have been taking metformin for some ten years now .The veterans lab told me my B-12 count was low ,and to take 1000MCG tablets as soon as possible . I have been taking the B-12 for f4ive monthe noe ,a blood test indicated t

Posted by: fwman | Dec 29, 2008 03:38 PM

Hi fwman,

I'm not sure what your question is - it looks like it got cut off...?

Posted by: acampbell | Jan 05, 2009 09:33 AM

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