Diabetes Forecast

Avoiding Lows from Late Evening Workouts

What to Know

Exercise in the evening can lead to low blood glucose levels (hypoglycemia) in people with type 1 diabetes, because blood glucose levels tend to drop overnight. Knowing that, many people who would otherwise work out instead avoid exercise in the evening, despite American Diabetes Association recommendations that people with type 1 diabetes live a healthy, active lifestyle. For this study, researchers wanted to know whether a reduced long-acting basal insulin dose combined with a reduced rapid-acting bolus insulin dose before a low-glycemic- index snack would lower the risk of hypoglycemia after an evening workout in people with type 1 diabetes.

The Study

A total of 10 men with type 1 diabetes enrolled in the study. The first study day, they took their usual total long-acting (basal) insulin dose; on the second study day they took 20% less. Both days, they took reduced doses of their usual rapid-acting insulin. In the evening, their dose of rapid-acting insulin (bolus) was 25% smaller than usual. A high-carbohydrate meal followed, then, an hour later, 45 minutes on a treadmill. An hour after running, participants took half their usual dose of rapid-acting insulin and ate a low-glycemic- index meal. At home, they ate a low-glycemic- index bedtime snack. Researchers took fasting blood samples each day and monitored glucose levels for 24 hours before and after exercise.

The Results

When participants took their usual dose of long-acting basal insulin, hypoglycemia occurred 6 hours after exercise. However, when participants took the 80% long-acting basal insulin dosages, they did not have hypoglycemia for up to 24 hours.


People with type 1 diabetes may reduce the risk of post-exercise hypoglycemia by reducing their insulin doses and eating low-glycemic- index foods right after an evening workout and before bed. Knowing that such modifications can help prevent hypoglycemia should reduce fears of exercise and encourage a more active lifestyle. The study did have some shortcomings, though. It was a very small study, which made comparing insulin doses and timing difficult. Also, it did not include women or people who were physically inactive. And, it did not include people who use insulin pumps.

Insulin therapy and dietary adjustments to normalize glycemia and prevent nocturnal hypoglycemia after evening exercise in type 1 diabetes: a randomized controlled trial, BMJ Open Diab Res Care 2015;3:1 e000085 http://dx.doi.org/10.1136/bmjdrc-2015-000085

The information on this screen does not take the place of care from your doctor or other health care provider. If you have general questions about diabetes or diabetes-related research, e-mail askada@diabetes.org or call 1-800-DIABETES (800-342-2382).



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