Checking Blood Sugar

Institutes & Services > Diabetes

Checking Blood Sugar

Checking your blood sugar (blood glucose) is important. Changes in blood sugar are common and can vary greatly throughout the day depending on what you eat, your activity, and medications you take.

  • Write your blood sugar results in your diary.
  • Take the diary with you to your regular doctor appointments.
  • The doctor or the diabetes educator will review and discuss your results with you.
  • Your doctor may adjust your medicine if your blood sugar is too high or too low.
  • The diary will also help you see how your meals, activity and medicines work together to control your blood sugar.
  • Controlling your blood sugar can delay or prevent diabetes complications such as heart attack, stroke, or blindness.

How do I check my blood sugar?

You will use a blood glucose meter to check your blood sugar several times a day. A meter is a small device that tests a tiny drop of blood and then displays your blood sugar level at that moment. A lancet is a device used to prick the skin to get the drop of blood. The results are used to make decisions about food, physical activity, and medications.

Areas other than the finger maybe used such as the fleshy part of the hand, the forearm, the outer thigh, the calf or the stomach. Experts recommend using the side of the fingertip to get the most accurate result. There are times that other sites should not be used because the result may be less accurate. These times include:

  • If your blood sugar is likely to be low
  • If you have trouble knowing your blood sugar is low (Hypoglycemia Unawareness)
  • If less than 2 hours after starting a meal
  • You have been physically active

Talk with your doctor or pharmacist to see what meters and supplies are covered by your insurance. If you do not have insurance, store brand meters and supplies are usually less costly.

What are the blood sugar targets for people with diabetes?

For most people, the American Diabetes Association recommends

  • When I wake up and before meals: 80 to 130 mg/dL 
  • 2 hours after starting a meal: below 180 mg/dL 

When is the best time to check blood sugar and how often?

Most people check their blood sugar after fasting (first thing in the morning before they eat) and before other meals. Your doctor may ask you to test your blood sugar after a meal (post-prandial) when your blood sugar may be higher. Usually a post-prandial blood sugar is checked 2 hours after eating.

Other times you may want to test are:

  • When you have symptoms of high or low blood sugar.
  • When you are ill, especially if you are throwing up or dehydrated.
  • Before, during and after exercise.
  • Before you go to sleep.

If you are using the results to decide on how much insulin to take, you will need to check your blood sugar several times during the day. Some people only need to check once or twice a day. If you are making medication changes, changing your activity or meal plan, if you are pregnant or if you are ill, you may need to check more often. Your health care team can help you to decide how often you should test.

How do I know my results are accurate?

Follow your meter’s instructions when doing your check.

  • Keep your meter clean.
  • Check test strips to make sure they are not past their expiration date.
  • Do not leave testing supplies in a hot car or direct sunlight, or in the freezer.
  • Make sure skin is clean and dry before testing.
  • Make sure your blood sample is big enough.
  • Check your meter with control solution as recommended by manufacturer.

All meters have a 1-800 phone number on the back in case you have questions about your meter. Your doctor will write prescriptions for your glucose meter and supplies. Insurance pays part of the cost of meters and supplies. Store brand meters and supplies may be less expensive if you do not have insurance.

Check with your doctor and your healthcare team to make sure these goals are correct for you.

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