When should I test my blood sugar level?

Ronald Tamler, MD
Endocrinology Diabetes & Metabolism
Depending on the medication you're taking, you may need to check your blood sugar only once a day. In this video, Ronald Tamler, MD, clinical director of the Mount Sinai Diabetes Center, discusses blood sugar testing.

This is a great and very necessary question.

First, take your blood sugar when your rise in the morning.

About two hours after breakfast take your blood sugar again.

If you get insulin or medication before dinner, take your blood sugar an hour before dinner.

If you take insulin at night take your blood sugar one hour before that.

If you are ill or extremely stressed take your blood sugar at least every four hours.

Before exercise take your blood sugar. If your reading is lower than normal you may need a snack: especially before strenuous exercise such as shoveling snow or swimming.

A key to successful diabetes management is knowing blood glucose readings.

Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
Though all blood sugar readings are helpful, certain readings -- such as those taken in the morning, before meals, two hours after meals, and before bedtime -- provide particularly valuable clues as to whether your overall diabetes management is working well. You and your doctor may come up with a testing schedule; if not, here is a common approach that will provide plenty of information without your having to test your sugar constantly.

Common monitoring pattern:

Day 1
  • Check your fasting sugar first thing in the morning, before
           breakfast or any activity.
  • Check again 2 hours after breakfast (start counting the time at
           the beginning of the meal).
Day 2
  • Check right before lunch.
  • Check again 2 hours after lunch.
Day 3
  • Check right before dinner.
  • Check again 2 hours after dinner.
Day 4 and after
  • Repeat the above cycle, choosing a different meal each day.
  • If there are several hours between the after-dinner test and when
           you go to bed, do a pre-bedtime test some days.
  • On a few occasions, set an alarm clock and do a test in the middle
           of the night (2 or 3 A.M. for most people); this is especially
           valuable if you wake up with a high blood sugar level or do
           not sleep well.
Be sure to record each number in a separate column so that all the pre-breakfast values are in one column, all the after-breakfast values are in a separate column, etc.  This will allow you to quickly see where you often have trouble with blood sugar control. 
The Best Life Guide to Managing Diabetes and Pre-Diabetes

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The Best Life Guide to Managing Diabetes and Pre-Diabetes

Bob Greene has helped millions of Americans become fit and healthy with his life-changing Best Life plan. Now, for the first time, Oprah's trusted expert on diet and fitness teams up with a leading...

Continue Learning about Diabetes


Diabetes mellitus (MEL-ih-tus), often referred to as diabetes, is characterized by high blood glucose (sugar) levels that result from the body’s inability to produce enough insulin and/or effectively utilize the insulin. Diabetes ...

is a serious, life-long condition and the sixth leading cause of death in the United States. Diabetes is a disorder of metabolism (the body's way of digesting food and converting it into energy). There are three forms of diabetes. Type 1 diabetes is an autoimmune disease that accounts for five- to 10-percent of all diagnosed cases of diabetes. Type 2 diabetes may account for 90- to 95-percent of all diagnosed cases. The third type of diabetes occurs in pregnancy and is referred to as gestational diabetes. Left untreated, gestational diabetes can cause health issues for pregnant women and their babies. People with diabetes can take preventive steps to control this disease and decrease the risk of further complications.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.