Exercise and Blood Glucose Levels…

Avoiding Low Blood Glucose Levels During Exercise

Avoiding Low Blood Glucose Levels During Exercise

Get the benefits of exercise while reducing your risks

Exercise, along with diet and medication, is key to lowering your blood glucose levels. But what happens if, after starting an exercise program, you think that your blood glucose levels are dropping too low (hypoglycemia)? What should you do?

Hypoglycemia is not defined by a particular blood glucose level alone, but usually occurs at glucose levels below 70 milligrams per deciliter (mg/dL) and is often accompanied by symptoms that include sweating, tremors, nausea or weakness. Because people with diabetes are prone to having their blood sugar drop during exercise, a good basic guideline is to make sure your glucose level is at least 100 mg/dL before you begin an exercise session to give you some margin for safety.

Be aware that when you exercise, it can be hard to tell if your glucose level is low. That’s because many symptoms of low blood glucose, such as fatigue and sweating, overlap with the changes people ordinarily experience when exercising vigorously. If you think that your blood glucose may be too low during or after exercise, check it with a blood glucose meter to determine whether it really is low. Low blood glucose levels may cause you to experience other symptoms, such as shaking and hunger, which you usually don’t experience just by exercising.

Is hypoglycemia a risk?

The risk depends on the person. In general, light exercise for less than 10 minutes is probably not going to affect your blood glucose levels very much. After moderate or strenuous exercise, however, your blood glucose levels can be expected to drop. Testing before, during and after exercise will tell you how much it drops and whether it drops to unsafe levels.

Before you begin an exercise program, consult your primary care provider and others on your health care team. They can help you develop an appropriate exercise program. They also can help you determine the best time to exercise and how to avoid hypoglycemia.

For example, if you use insulin, you may not want to schedule exercise when your insulin level peaks. Because peaks of insulin lower your glucose levels, adding exercise during this time could bring blood glucose down even more and cause it to go too low. If you’re on oral medications, think about the timing of their effects. Also, you probably shouldn’t exercise if you’ve gone several hours without food. One of the best times of the day to exercise is after a meal. This ensures that there is some glucose in your body but also helps to lower the spike in blood glucose that is caused by eating.

Is hypoglycemia a risk?In order to help prevent hypoglycemia, you need to think about many aspects of your day-to-day diabetes care. If your blood glucose levels are frequently too low during or after exercise, check with your physician or diabetes educator. You may be instructed to modify your exercise regimen. You also may be told to check your blood glucose levels before exercising and, if necessary, to eat a small snack beforehand.

Generally, if your blood glucose is less than 100 mg/dL before exercise, you should eat at least one carbohydrate choice (15 grams) before your workout. If your exercise session lasts longer than an hour, you should consider retesting when you finish to see if you need another snack, even if you feel fine. Improvement in glycemic control from exercise can actually last 12 to 72 hours depending on the duration and intensity of the exercise. Continue to monitor your blood sugar levels daily as recommended by your doctor or diabetes educator.

Always keep some quick sources of sugar handy just in case you need it while exercising. This can be glucose tablets, glucose gel, hard candy (not sugar free), fruit juice, raisins, or a regular soft drink (not diet).


  1. 1If you’re new to exercise, start slowly, and test your blood glucose before, during and after exercise to determine the effects of exercise on your blood glucose levels.
  2. 2Always carry a source of carbohydrate with you. Eat something even if you don’t have a blood glucose monitor to test your level but you feel the symptoms of a low blood sugar level.
  3. 3If you’re concerned about low blood glucose levels, exercise in a public place or bring a cell phone. If your blood glucose continues to drop when you check it several times during exercise (a very uncommon occurrence), you may need to seek immediate medical attention. You may also want to instruct someone to recognize the signs of severe hypoglycemia and what to do should it develop.
  4. 4Be on the lookout for hypoglycemia not only when you exercise, but up to 72 hours later. Keep monitoring for symptoms of low blood glucose and your blood glucose levels to detect very low blood glucose.

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