How Often to Test Your Blood Glucose

Checking your blood sugar is an important part of having diabetes. But before you grab your meter and check your blood glucose level, ask: Why am I checking now? How will I use the information? If you don't know, find out before you waste a test strip. Our blood sugar guide answers your questions on when and how often to test when you have diabetes.

Make the Most of Your Meter

How often should you check your blood sugar? The answer depends on the type of diabetes you have, your blood glucose level targets, and more practical matters, such as whether you can afford the test strips.

Recent studies have indicated that people with type 2 diabetes (PWDs type 2) who don't use medications but do self-monitor blood glucose may not see much difference in blood glucose control compared with people who don't self-monitor. But using a meter can provide much helpful information to guide you in selecting:

  • foods
  • portions
  • exercise
  • medication doses

From finding how often to test to discovering how accurate your meter is, we'll show you what you need to know about testing your blood sugar.

When Is the Best Time to Test Blood Sugar?

Many newly diagnosed PWDs type 2 are instructed to check fasting blood glucose. Diabetes educator Deb Bjorsness, R.D., CDE, from Great Falls, Montana, says: "It's pretty common for docs to say, 'Just check first thing in the morning; that's good enough.'"

Bjorsness has seen when it isn't good enough. "People come in and the only time they test is first thing in the morning, and their A1C has come back 8, 9, or 10 percent. That's the beauty of doing blood sugars at other times of the day, including postprandials [after meals], to see where the problem is."

If you've settled into a diabetes plan and your fasting blood glucose results are within your goal range, a better use of the next strip would be to check at a different time. There are many times when you can test your blood glucose, such as when you're sick, you start a new medication, or you're under a lot of stress. Some standard blood glucose checkpoints include:

  • fasting
  • before meals
  • after meals
  • before bed
  • during the night

Follow these easy tips to lower you blood sugar.

Consider Testing Before a Meal

If you're on a flexible insulin plan (multiple daily injections of long- and rapid-acting insulins or an insulin pump), check before meals to help determine doses. If you have type 2 diabetes and are starting insulin therapy with one injection a day, your doctor will probably adjust the dose based on your daily fasting results.

Below are target blood glucose guidelines for adults with diabetes who have no other health issues. The two major diabetes organizations differ on their recommendations. Ask your doctor about specific targets for you.

Guidelines for testing before a meal:
American Diabetes Association: 70-130 mg/dl
American Association of Clinical Endocrinologists: Under 110 mg/dl

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Consider Testing After a Meal

If you're on a flexible insulin plan (multiple daily injections of long- and rapid-acting insulins or an insulin pump), check before meals to help determine doses. If you have type 2 diabetes and are starting insulin therapy with one injection a day, your doctor will probably adjust the dose based on your daily fasting results.

Whether or not you use medications to control blood glucose levels, check one to two hours after a meal (check both before and after the same meal for precise data) to see how certain meals affect your blood glucose. This is especially helpful when you are first diagnosed.

But once you've seen the effects of certain foods and portions, you may not need to check every time, says endrocrinologist Tom Elasy, M.D.

Below are target blood glucose guidelines for adults with diabetes who have no other health issues. The two major diabetes organizations differ on their recommendations. Ask your doctor about specific targets for you.

Guidelines for testing after a meal (postprandial):
American Diabetes Association: Less than 180/mg/dl (1-2 hours after start of meal)
American Association of Clinical Endocrinologists: Less than 140 mg/dl (2 hours after meal)

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Consider Testing at Night

Bedtime checks (at least two hours after the evening meal) are recommended for:

  • people on multiple daily injections.
  • people who use insulin pumps.

Checking before bed may be recommended if you take basal insulin such as Levimir or Lantus once a day at bedtime or split your does into two injections.

What you should know about middle-of-the-night checks:

  • People who use insulin may be advised to do a check between 2 a.m. and 3 a.m. to reveal any nighttime hypoglycemia (blood glucose under 70 mg/dl).

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Consider Testing Before and After Exercise

Check to see how exercise affects blood glucose by testing immediately before and after exercise. Aerobic activity tends to lower blood glucose, even hours after stopping; strength training such as weight lifting may temporarily increase blood glucose, but it has long-term glucose-lowering benefits.

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Don't Forget These Important Times to Test

You should also test your blood sugar if you:

Are sick or have an infection. Illness can send blood glucose levels up. Check your glucose every two to four hours. If it's:

  • over 250 mg/dl, check your urine for ketones (a sign the body is burning fat for energy and may have insufficient insulin);if ketones are present in more than trace amounts, call your doctor.
  • over 250 mg/dl for more than six hours, call your doctor.
  • over 350 mg/dl even once, call your doctor.

Start a new medication. A prescription or over-the-counter medicine for a condition other than diabetes may affect glucose levels. Steroids are one example.

Are under a lot of stress. Emotional stress may lead to higher blood glucose numbers. Exercise -- even just a walk around the block -- helps reduce stress and glucose levels.

Feel as though your blood glucose level is too low. If your meter confirms it with a number of 70 mg/dl or less, eat 15-20 grams of pure glucose (tablets or gel) or drink 1/2 cup fruit juice or regular soda. Wait 15 minutes and check again.

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Get the Best Use Out of Your Strips

There are many times you could check. How often should you? "Everyone wants black-and-white answers," says Mary M. Austin, R.D., CDE. "It's not how often you do it; it's what you do with the information."

Endrocrinologist Tom Elasy says people and health care providers need to distinguish between the intensification stage of diabetes -- when diabetes is newly diagnosed or when the treatment plan is being changed -- and the maintenance phase -- when glucose goals are reached.

How to Best Use Strip Allotment
Medicare covers 100 test strips every three months for a PWD who doesn't use insulin. For someone newly diagnosed with type 2, how is this allotment best used? "I'd use a lot early to learn about the person," Elasy says. "And for them to learn a lot about themselves: how physical activity and diet and medication affect their blood sugar."

"But once that lesson is learned, that intensity is not required," he says, although as the disease progresses, renewed testing often is necessary. "Folks that are not on any medications at all, do they need to monitor twice a day? Of course not. Would it be helpful if they monitored at least once or twice a week just to keep track? Absolutely. Monitoring has a powerful, positive effect on how you subsequently eat or the likelihood that you'll take a walk."

However often you choose to check in the maintenance phase, move the times around. And if you're not willing to check regularly, diabetes educator Deb Bjorsness says to at least do some spot checks. "Two hours after your biggest meal is probably your best time for information."

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What You Need to Know About Glucose Meter Accuracy

Blood glucose targets are given as ranges because no one, even people without diabetes, maintains a constant number. Here are some things that may affect the accuracy of your results:

User error. Suspicious of the results? Read and follow the user guide instructions. Store your meter and strips away from sunlight and temperature extremes. Check the viability of each new bottle of test strips by running a check using glucose control solution.

Laboratory versus at-home results. Meters intended for self-monitoring are allowed to vary by as much as 20 percent from the results laboratory equipment would give. And it depends on how the meter reads the sample: as plasma or whole blood. Plasma glucose may be as much as 15 percent higher.

Location of the blood. Blood glucose levels differ within the body. Rapid changes from dosing insulin or eating show up first in blood obtained from the fingertips.

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Keep Track of Your Blood Glucose Checks

Glucose checks should be tracked in the form you prefer -- and can be used to spot patterns and make changes when levels are out of your target range.

Which is better: a paper logbook or fancy software that lets you download results and make graphs?
"The vast majority of people just need simple, basic devices," says endocrinologist Tom Elasy, M.D. "We're advancing technology the wrong way. Fun graphs and figures -- that's information that doesn't inform."

Diabetes educator Deb Bjorsness, R.D., CDE, agrees. "The people who download into a computer are not likely to do it immediately. They might do it in a month. The beauty of writing the results down in a logbook right then is you can see them day to day."

Make use of any data you collect:

  • Circle numbers that are outside your target range.
  • Three glucose levels from the same time of day that are out of range are a pattern. If you don't know what to do about the pattern, call your health care provider.
  • If you run out of logbooks, go to the meter manufacturer Web sites. Some have log sheets you can print.

Get a Good First Drop for Accurate Blood Glucose Results

Diabetes educator Deb Bjorsness, R.D., CDE, suggests these steps to getting a good drop of blood on the first stick -- with the least pain -- and thus an accurate result:

1. Wash. "It's amazing how many people don't wash their hands," Bjorsness says. "Say you eat an apple. You don't realize you have apple residue on your fingers. If you don't clean your hands, you could have a blood sugar result that is artificially high. If you use insulin, that can be a real issue." Bjorsness recommends using soap and warm water. "Save the alcohol pads for when you are out and about and don't have access to a sink," she says.

2. Shake. Give your hands three to five shakes below your heart to get the blood down to the fingertips. For those of you who remember shaking down a mercury thermometer, that's the snap you want.

3. Stick. Set your lancet to the right depth for you. "You need a depth on the device to get just enough blood without having to squeeze the life out of your finger. Don't go deeper than you need." For less pain, use the sides of your fingers, which have fewer nerve endings than the pads. Or try an alternate lancing site, such as the fleshy parts of your palm or forearm.

4. Milk. Gently milk the finger down. Don't squeeze hard or you might change the composition of the blood, affecting the result.

Know Your Blood Glucose Targets

Before you use another test strip, make sure you know your blood glucose targets.

In a telephone survey of 500 people with type 2, over half of those taking no diabetes medication, 30 percent of those taking pills, and 12 percent of those taking insulin did not have blood glucose level targets. See our blood glucose guidelines for general targets. Then ask your health care provider what ranges are right for you.

Type of test: Fasting (before breakfast)
American Diabetes Association recommends: 70-130 mg/dl
American Association of Clinical Endocrinologists recommends: Under 110 mg/dl

Type of test: A1C (shows blood glucose levels over time)
American Diabetes Association recommends: Less than 7 percent (under 156 mg/dl expressed as estimated average glucose)
American Association of Clinical Endocrinologists recommends: 6.5 percent or less (under 110 mg/dl expressed as estimated average glucose)

Note: A woman who is pregnant or trying to get pregnant will have lower target numbers for the health of her baby. Children have higher target numbers. Elderly people, especially those who have cardiac disease, may have higher target numbers.

Marie McCarren's books include A Field Guide to Type 2 Diabetes (American Diabetes Association, 2004) and The American Diabetes Association Guide to Insulin & Type 2 Diabetes (2007).

Tips to Lower Blood Glucose

You can achieve lower blood glucose numbers! And doing so can help you live a happier, healthier life with diabetes. Feel better and reduce your risk of diabetes complications when you lower your blood sugar levels to your target range. We can help you get there.

Tips to Lower Blood Glucose

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