High blood glucose is the defining characteristic of diabetes: It’s what leads to a diagnosis of diabetes, and it’s what can lead to long-term diabetes complications if sustained over time. Consequently, the medicines prescribed to treat diabetes lower blood glucose in one way or another. Exercise, too, usually lowers blood glucose, which is one of the reasons it’s an important part of a diabetes treatment regimen. But too-low blood glucose, or hypoglycemia, is no good, either, since it can cause you to lose consciousness.
“Always bear in mind that your own resolution to succeed is more important than any other.” — Abraham Lincoln
Food raises blood glucose level, and certain other things can, too, such as illness and other forms of physical or mental stress. The challenge of managing diabetes, therefore, is to balance all of the things that can raise blood glucose (including the diabetes itself) with those that can lower it, so that your blood glucose level stays within a fairly narrow range. Staying in this range will not only help to prevent complications, but it will enable you to feel your best, both mentally and physically.
So what is that range, and how do you stay there?
Recommendations for blood glucose targets
Both the American Diabetes Association (ADA) and the American College of Endocrinology (ACE) have published recommendations regarding target blood glucose ranges. The ADA recommends aiming for a blood glucose level between 70 and 130 mg/dl before meals and a level lower than 180 mg/dl two hours after the start of meals. The ACE recommends a goal of blood glucose lower than 110 mg/dl before meals and lower than 140 mg/dl two hours after the start of meals.
While somewhat different, both of these sets of recommendations are based on research showing the level of blood glucose control needed to prevent long-term diabetes complications (such as nerve damage, kidney disease, and eye disease), while avoiding the short-term complication of hypoglycemia.
These recommendations are intended to guide the treatment of diabetes for most nonpregnant adults with diabetes, but they may not be right for every individual. Your health-care provider should discuss with you the blood glucose target range that is right for you. If you are elderly or have certain other medical conditions besides diabetes, you may be advised to keep your blood glucose level in a higher range to avoid hypoglycemia. Women who are pregnant or are contemplating becoming pregnant are usually advised to follow ADA or ACE guidelines to maintain lower blood glucose levels than adults who are not pregnant.
Keeping your blood glucose within the desired range
Your health-care provider will work with you to develop a plan to keep your blood glucose level within the desired range.
Your overall diabetes plan should include an individualized meal plan that helps you choose the types and amounts of food to eat to prevent your blood glucose level from rising too high after meals. If you have other health problems such as high blood pressure, high cholesterol, or overweight, your meal plan should be designed to help improve those conditions, as well.
Your diabetes plan should also include a plan for regular physical activity to keep your heart and blood vessels healthy and to lower or prevent insulin resistance, which contributes to high blood glucose in people with diabetes. Cells that are insulin resistant require more insulin than normal to take in glucose from the bloodstream. Most people with Type 2 diabetes and some with Type 1 have some degree of insulin resistance.
Your plan may include taking oral or injected medicines on a particular schedule. Learning to inject insulin or other medicines requires training and practice, and sticking to any drug regimen takes effort and discipline. A certified diabetes educator can help you master both the techniques and planning necessary to maintain a medication plan.
Your plan may also include visits to a mental health-care provider, such as a psychologist or social worker, to talk about the social, emotional, and practical effects of diabetes on your life. While you might not think that talk therapy could directly affect your diabetes control, in fact, having the opportunity to express your feelings, and feeling supported in your efforts, can have a big effect on your willingness to carry out your diabetes care tasks at all.
Given how many components there are to a diabetes care plan and how much there is to learn, many people find it useful to attend diabetes education classes, particularly when first diagnosed. Diabetes education classes are commonly given at hospitals, clinics that provide diabetes care, and, sometimes, medical offices. Most classes meet for several sessions, covering different topics at each session, and ideally providing time for questions and discussion among class attendees. Many insurance plans, including Medicare, cover a certain number of hours of diabetes education when a person is first diagnosed and each year thereafter.
What to know about monitoring your blood glucose
Once you and your health-care provider have worked out a diabetes control plan for you and have settled on a target blood glucose range, you need to monitor your blood glucose periodically to see whether you’re in that range. That means you’ll need a blood glucose meter, which your physician or diabetes educator can help you choose and teach you to use. Most insurance plans cover only selected meters and test strips. However, if you are likely to have trouble using the meter your insurance normally covers because of visual impairment, shaky hands, or something else, you or your health-care provider can petition your insurance company for a meter that better fits your needs. Some people who want very frequent information about their glucose level use continuous glucose monitoring devices in addition to blood glucose meters. To read more about continuous monitors, see “Continuous Glucose Monitoring.”
How often you use your meter each day depends on the type of diabetes you have and your individual treatment plan. If you use an insulin pump or take multiple doses of insulin, the ADA recommends checking your blood glucose “prior to meals and snacks, at bedtime, occasionally [after meals], prior to exercise, when [you] suspect low blood glucose, after treating low blood glucose until [you have normal blood sugar], and prior to critical tasks such as driving.”
Even when you don’t use insulin, monitoring can help show you the effects of your food choices, physical activity, medicines, and stress-management efforts. Monitoring at different times on different days (as opposed to monitoring at the same times every day) gives you valuable information about your blood glucose level over the course of the day. (See “Twice-a-Day Monitoring Schedule” for a suggested schedule.) It allows you to see patterns in your blood glucose levels, such as highs or lows at particular times of day. Sharing this information with your health-care provider can help him make the best recommendations for fine-tuning your treatment.
When you check your blood glucose level, keep in mind that you are shooting for a range of blood glucose levels, not an exact number. If your blood glucose readings before lunch are 87 mg/dl, 97 mg/dl, 109 mg/dl, and 101 mg/dl for four consecutive days, they may appear to be fluctuating, but all of these levels are within the ADA and ACE target ranges, so they would not call for an adjustment in treatment.
The target ranges in the ADA and ACE guidelines are for blood glucose levels just before meals and two hours after the start of meals, and these are the times of day when many people routinely monitor. Many people also monitor at bedtime to determine whether a snack may be necessary to prevent hypoglycemia overnight. People who use insulin are advised to monitor before driving so that they catch — and treat — low blood glucose early and not develop hypoglycemia while driving. Other times to monitor are when you feel any symptoms of hypoglycemia (such as feeling tired, hungry, sweaty, shaky, dizzy, grouchy, or confused) or when you simply don’t feel well. Not every ill feeling is a result of having a high or low blood glucose level, but it’s better to check so that if high or low blood glucose is the problem, you can take steps to correct it.
No matter what your usual monitoring schedule, here are some reasons to check your blood glucose more frequently, at least temporarily:
- You are ill. (Even if you cannot eat, your blood glucose may be high because of the stress of the illness.)
- You have recently changed diabetes medicines.
- You have recently changed your meal plan.
- You have recently changed your level of physical activity or are trying a new type of sport or exercise.
- You are experiencing increased amounts of stress in your life.
- You are at a stage in your menstrual cycle when you usually experience rising or falling blood glucose levels.
Troubleshooting glucose meter problems
When used correctly, your blood glucose meter should provide accurate readings. If you think something’s not right with your blood glucose monitoring results, start with the basics:
- Did you calibrate the meter for the test strip you used? Most newer meters don’t need to be calibrated, or coded, but others won’t give an accurate reading unless you enter the code number on the box or vial of test strips into the meter.
- Did you apply enough blood to the test strip? A too-small blood sample will yield an inaccurate reading.
- Was the finger that you pricked clean?
- Are your test strips expired?
- Have your test strips been stored properly? Strips that have been exposed to very high temperatures may give inaccurate results.
- Is the meter at room temperature? Your blood glucose meter may not work accurately at cold or very hot temperatures.
- Does the meter need new batteries? (Check the display screen.)
- Has the meter been dropped or damaged?
If you think you’ve done everything right but still don’t trust your results, do a test using the control solution that is made for your meter. Control solution is a glucose solution that is designed to give a reading in a predetermined range when applied to a blood glucose test strip. The predetermined range will be marked on the vial of test strips or possibly on the bottle of control solution itself. If your reading is within the range indicated, your meter and strips are working properly. If not, make sure your control solution isn’t expired, and repeat the test. If your results are still outside the control solution range, call your meter’s customer service number for help.
Another tool to see how well your diabetes plan is working is the A1C test, also called the glycosylated hemoglobin, or HbA1c, test. This blood test gives an indication of overall blood glucose control over the previous 2–3 months by measuring the percentage of one type of hemoglobin molecules (found in red blood cells) that are attached to glucose molecules, or are glycosylated. This percentage gives a very good estimate of your average blood glucose level over that time. Currently, the ADA recommends a target A1C of less than 7% (equivalent to an estimated blood glucose average of 154 mg/dl), while the American College of Endocrinology (ACE) recommends a target A1C of 6.5% (equivalent to an estimated blood glucose average of 140 mg/dl) or lower. In research studies, higher A1C levels have been associated with a higher risk of diabetes complications.
The ADA’s recommended frequency for measuring A1C is two to four times a year. In the near future, your health-care provider may tell you your results both as a percentage and as an estimated average glucose level to make it easier to compare to your home blood glucose monitoring results. (To see how A1C percentages compare to the results you get on your meter, see “Average Blood Glucose.”)
An A1C test result that is higher than expected usually indicates that there are times when you are not monitoring that your blood glucose level is high. Varying the times of day you monitor can help to uncover when these times are and assist your health-care provider in making appropriate treatment recommendations.
When things go wrong with your glucose levels
In spite of your best efforts, it’s likely there will be times when your blood glucose level is higher or lower than your target range. Knowing how to respond is an important part of your diabetes care plan.
When your blood glucose gets too high, it is called hyperglycemia. Warning signs may include feeling very thirsty, having to urinate often, feeling very tired or weak, or having blurred vision. In many cases, however, hyperglycemia causes no symptoms at all.
Hyperglycemia can be caused by not taking your medicine as prescribed, which can happen for any number of reasons, including forgetting to take it, choosing not to take it, running out of medicine, or having a problem with your method of medicine delivery, such as a malfunctioning insulin pump. Some diabetes medicines, including insulin, can also lose effectiveness if they are old or have been stored improperly. Hyperglycemia can also be caused by an illness or infection, by certain medicines used to treat conditions other than diabetes, by eating too much, or by being less active than usual.
How you respond to high blood glucose depends in large part on how high it is and what the likely cause is. If you’ve just eaten a meal and your blood glucose level is somewhat higher than you’d like, taking a walk and drinking some water can help to bring it down, and reassessing your portion sizes, food choices, and carbohydrate intake at that meal may help to prevent high blood glucose in the future. If high blood glucose does not appear to be related to a recent meal, think through the other possible causes, such as forgetting to take a dose of medicine or coming down with a cold, to determine what might be going on.
Having a plan to respond to high blood glucose is important, because prolonged hyperglycemia can lead to diabetic ketoacidosis (DKA), a life-threatening complication. People with Type 1 diabetes are at higher risk of developing DKA than people with Type 2 diabetes, but it can happen in people with Type 2, particularly if they have a severe infection or injury.
DKA develops when there is not enough insulin in the body to use glucose for energy. When that happens, stored fat is broken down for energy instead, and acid by-products called ketones are created in the process. Ketones build up in the blood and eventually spill into the urine. The combination of high blood glucose, high blood ketones, and dehydration can lead to coma or even death.
It is recommended that you check your blood or urine for ketones if your blood glucose is over 240 mg/dl, if you are sick or have an infection, if you are under a lot of stress, if you have lost weight and don’t know why, or if you are not feeling well (even if your blood glucose is not elevated). One of the most common signs of DKA is having a sweet, fruity odor to your breath. Other signs include nausea, abdominal pain, flushed skin, rapid breathing, loss of appetite, or unconsciousness. The people you spend time with regularly should be aware of the warning signs of DKA since they can easily be mistaken for the flu.
Hypoglycemia is when your blood glucose is too low. It can happen if you skip a meal or snack, eat a meal or snack later than usual, eat less than usual, exercise more than usual, take too much diabetes medicine, or drink alcohol on an empty stomach. Your body will usually give you warning signs of low blood glucose, which may include feeling tired, hungry, sweaty, shaky, dizzy, grouchy, or confused.
When you experience these symptoms, it is important to respond quickly. If you can check your blood glucose level with your meter, do so. If you can’t get to your meter quickly, it’s safer to go ahead and treat yourself for hypoglycemia than to wait until you can check with your meter. If your blood glucose level is 70 mg/dl or lower, eat or drink something containing 15 grams of carbohydrate, and recheck in 15–20 minutes. If your blood glucose has not risen in that time, eat or drink another 15 grams of carbohydrate. If it has risen by at least 30 mg/dl and is above 70 mg/dl, you do not need to eat or drink more. However, if it is almost time to eat a meal, go ahead and eat the meal.
Some people have a higher risk of developing hypoglycemia than others. Those at higher risk include anyone who uses insulin and anyone who takes one of the following drugs: chlorpropamide (brand name Diabinese), tolazamide (Tolinase), tolbutamide (Orinase), glyburide (DiaBeta, Glynase, and Micronase), glipizide (Glucotrol, Glucotrol XL), glimepiride (Amaryl), combination drugs that contain glyburide, glipizide, or glimepiride (such as Glucovance, Metaglip, Avandaryl, and Duetact), repaglinide (Prandin), combination drugs that contain repaglinide (Prandimet), and nateglinide (Starlix). People who take multiple medicines for Type 2 diabetes are also at a higher risk of hypoglycemia. People who control their Type 2 diabetes with diet and exercise or who take only metformin (Glucophage and other brands) are at low risk for hypoglycemia.
Anyone who is at risk of developing hypoglycemia is advised to carry a source of 15 grams of carbohydrate in case of low blood glucose. Portions of food and drink that contain 15 grams of carbohydrate include 3 regular-size marshmallows; 3–5 Life Savers, sugar cubes, or glucose tablets; and half a cup (4 ounces) of fruit juice or regular (nondiet) soft drink.
If you use insulin, your doctor may prescribe a glucagon emergency kit for you, to be used in the event of severe hypoglycemia, when you are unable to treat yourself or safely swallow food or liquids. Glucagon must be administered by injection, so you will want to teach your family members, coworkers, and possibly others how to use it and to be sure they know where your kit is located. Glucagon kits also have easy-to-use instructions with pictures to help the person giving the injection.
People who have had high blood glucose for a sustained period may experience symptoms of hypoglycemia at blood glucose levels higher than 70 mg/dl. This is because the brain has adapted to having high blood glucose. If you have symptoms of hypoglycemia when your blood glucose level is in the normal range, do your best not to eat or drink carbohydrate in response. Drinking water and taking a walk may help take your mind off the symptoms you’re feeling. Your brain will eventually adapt to normal blood glucose levels.
Blood glucose that is dropping quickly — which can be caused by taking too much medicine or by engaging in more physical activity than usual — may similarly cause signs and symptoms of hypoglycemia, even when the actual blood glucose level is higher than 70 mg/dl. Eating or drinking carbohydrate in response is not recommended as long as your blood glucose is in a normal range, but you may need to recheck your blood glucose level periodically to make sure it isn’t dropping too low. If you frequently experience rapid drops in blood glucose level, you will learn from experience when to have a snack, and when to wait out the symptoms of hypoglycemia.
Preventing problems: Monitoring your glucose levels often is key
One way to prevent problems is to monitor your blood glucose level often enough to pick up on small problems before they become big problems. This is particularly important for anyone who is at risk of developing hypoglycemia, as listed above, or hyperglycemia. People who use an insulin pump are at higher risk of developing hyperglycemia because only fast-acting insulin is used in a pump. If the pump malfunctions or becomes accidentally disconnected, there is no long-acting insulin in the person’s system to continue moving glucose from the bloodstream into the body’s cells, so high blood glucose can develop quickly.
Another way to prevent problems is to keep records of your blood glucose monitoring results and to look for patterns in your numbers. While an isolated high blood glucose level may have little significance, a pattern of high blood glucose levels at a particular time of day or during or after a particular activity is often a sign that some part of your diabetes treatment plan needs adjustment.
When you record your blood glucose monitoring results, it’s helpful to also jot down information about your day, such as your food intake, sleep schedule, level of physical activity, or stress level. This type of information may be useful in determining the cause of any out-of-range blood glucose levels or patterns of blood glucose levels. Some newer meters allow the user to “tag” blood glucose readings with notations such as “meal” or “exercise.” In addition, most major meter companies now make software that can display several days’ or weeks’ worth of blood glucose readings in a variety of charts and graphs. These can make it easier to see blood glucose patterns, and if you can print them out, they’re handy to share with your diabetes care provider.
However you keep your blood glucose records, take them and your meter to all of your diabetes appointments to show to your health-care provider. Your provider is there to help you work out any problems in your diabetes management, not to scold you for having problems, so be sure to speak up when things aren’t working well.
Frequently asked questions about blood glucose
While each person’s diabetes is unique, there are some common problems that diabetes care providers are often asked about, including the following:
Why would my blood glucose be higher in the morning than it is at bedtime the night before?
One possibility is that your liver is releasing lots of glucose into the bloodstream during the night, because the feedback mechanisms to prevent this from occurring are not working. Taking the drug metformin can help in this situation.
Another possible cause is the dawn phenomenon, in which hormones released during the normal waking process cause a rise in blood glucose in the early morning hours. In people who take insulin, adjusting their dose of long-acting insulin or the basal rate on an insulin pump may help to correct this.
Yet another possible cause is the Somogyi effect, in which the body responds to hypoglycemia during the night by releasing hormones that cause the liver to release glucose, thereby restoring blood glucose to a safe level. The treatment in this case is to prevent hypoglycemia during the night, which involves assessing and adjusting your evening meal and medicines.
Why would I have two identical A1C test results in a row when my home blood glucose monitoring results were completely different during the periods leading up to each test?
Your A1C level can be interpreted as an average of all blood glucose levels over three months. When you consider that the average of 76 and 140 is 108, and the average of 30 and 186 is also 108, you can see how three months of in-range blood glucose levels could yield the same A1C as three months that included some out-of-range blood glucose levels.
When your A1C level doesn’t seem to “match” your home blood glucose monitoring results, you may want to vary the times of day at which you check your blood glucose level with your meter. You may find there are times when your blood glucose level is high or low; if these fall into a pattern — for example, you have high blood glucose after lunch pretty much every day — you may need to make some adjustments to your diabetes management plan.
I have downloaded my meter. Now what do I do?
With most meters on the market today, you can transfer your blood glucose monitoring results from your meter to a software program on a computer using a cable provided by or purchased from the meter manufacturer. The software program will have a variety of ways of displaying your blood glucose readings, making it easier for you to assess your overall level of control as well as see patterns in your blood glucose levels, such as frequent highs or lows at particular times of day.
This information is useful to your health-care provider, too, so if you have access to a printer, take a copy of any charts, graphs, or other reports you make to your next appointment to discuss. The first priority when looking over your blood glucose history is to note any episodes of hypoglycemia and their likely cause. The second is to note whether your blood glucose levels first thing in the morning and before meals are within your target range. And then you will want to see whether your after-meal readings are within range.
Consistent problems in any of these areas may be addressed with changes to your medication, meal, or exercise plans. However, since it can be difficult to remember what you ate or when you exercised from one doctor appointment to the next, it helps a lot to keep some records of these details, particularly if you’re noticing out-of-range readings when you monitor your blood glucose.
When should I check my blood glucose after a meal to see if what I ate contained the amount of carbohydrate I thought?
If you want to evaluate how certain foods or amounts of food affect your blood glucose level, check it approximately two hours after you begin eating. You will get the most information if you also check before the meal, then compare the two readings.
Stay proactive about your diabetes care regimen
It’s not uncommon for people with either Type 1 or Type 2 diabetes to need some adjustments to their diabetes care regimen as their bodies, health, and life situations change over the years. Performing regular blood glucose monitoring and having your A1C level measured every three to six months can alert you and your health-care provider to when changes are needed.
Diabetes will be with you for a lifetime, but by being proactive in your care, optimal diabetes control can be yours for a lifetime, too.
Want to learn more about managing blood sugar? Read “What Is a Normal Blood Sugar Level?” “Managing Your Blood Glucose Ups and Downs”, and “Blood Sugar Monitoring: When to Check and Why,” then see our blood sugar chart.