How to Prevent Hypoglycemia During and After Physical Activity

The short- and long-term benefits of physical activity are undeniable, from both a physical and psychological standpoint. For people living with type 1 diabetes (T1D), physical activity also has tangible benefits for improving blood sugar management and preventing long-term complications. However, some planning and caution is required, because the large amount of glucose used by muscle cells during physical activity leads to an increased risk of hypoglycemia. 

Some people with T1D are afraid of physical activity, or don’t work out as much as they would like, because they are concerned about the risk of hypoglycemia. But there are strategies for minimizing that risk.

Limiting hypoglycemia during your workout

The first thing to take into consideration is the type of exercise, its duration and its intensity. A cardiovascular type of workout (e.g., running, swimming, biking, etc.) burns up a larger amount of glucose than resistance training (e.g., muscle building). There are two main ways to prevent hypoglycemia during cardiovascular exercise: reducing insulin and/or increasing carb intake. Which of these two methods is most effective? There are few studies that look at this, but one recent study looked at this issue among participants who did moderate-intensity cardiovascular activity for 45 minutes (stationary bike).

In that study, one group of individuals reduced their mealtime rapid-acting insulin bolus by 50% one hour before exercising. The participants in the second group did not reduce their mealtime insulin dose, but took a 15 to 30 g supplement of rapid-acting glucose during the activity. The second option turned out to be more effective at preventing hypoglycemia during exercise.

However, this study has several limitations:

  1. The participants did not try both methods, which means that the results could be due to individual differences.
  2. The size of the group was small.
  3. Only one type of physical activity was tested.

In short, it’s through practice and trial-and-error that you’ll be able to find the adjustment that works best for you. 

Limiting hypoglycemia after your workout

After your workout, depending on your blood sugar level, it’s recommended that you eat a snack with complex carbs and protein to reduce any risk of hypoglycemia. For example, you could have crackers with cheese or peanut butter.

There is an increased risk of hypoglycemia up to 48 hours after you finish exercising, because the muscle cells remain insulin-sensitive during that period. It’s recommended that you pay close attention to your blood sugar levels, especially at night. This could involve programming one or several alarms at night to measure your blood sugar level. If you use an insulin pump, it’s recommended that you reduce your nighttime basal insulin dose by 20%. This could be combined with a bedtime snack.

A few tips

It’s essential to have all the tools you need to plan and practise any physical exercise. To help you, the BETTER team has created an at-home training program that will motivate you. This program includes tables that will help you to adjust your insulin doses and carb intake. Click on this link.

Are you living with diabetes and 50 years of age or older? You could contribute to research by completing an online questionnaire on physical activity.

To learn more, click HERE.


  • Brazeau, A., Rabasa-Lhoret, R., Strychar, I., and Mircescu, H. (2008). Barriers to Physical Activity Among Patients With Type 1 Diabetes. Diabetes Care, 31(11), 2108-2109. doi:10.2337/dc08-0720
  • Eckstein, M. L., et al. (2020). Efficacy of Carbohydrate Supplementation Compared With Bolus Insulin Dose Reduction Around Exercise in Adults With Type 1 Diabetes: A Retrospective, Controlled Analysis. Canadian Journal of Diabetes. doi:10.1016/j.jcjd.2020.03.003