Hypoglycemia and physical activity: update on insulin reduction to safely perform aerobic exercise

One of the challenges of exercise for patients living with type 1 diabetes is the possibility of a hypoglycemic episode (low blood sugar). There are many ways to avoid having a low that usually involve either decreasing insulin or suspending its infusion or consuming carbohydrates. Recently a study (1) evaluated three strategies addressing when and how much to reduce insulin for individuals using an insulin pump.

They had seventeen individuals complete three 60-min treadmill exercise at a moderate intensity. They either suspended their pumps at the beginning of the exercise, reduced their basal rate by 80% 90 minutes before exercise, or reduced their basal rate by 50% 90 min before exercise.

They found that overall, a 50–80% basal rate reduction set 90 min before exercise improved glucose control and decreased hypoglycemia risk during exercise better than pump suspension at exercise onset. Interestingly, this approach with insulin reduction 90 min before exercise did not compromise glucose control after the exercise.

This recent study complements previous work done by our team showing that planning a similar (-80%) basal insulin reduction 40 minutes before exercise was not sufficient to prevent exercise-induced hypoglycemia (2).

The overall message for adults using insulin pump therapy and practicing a moderate intensity exercice is that when using basal insulin reduction as a strategy, a time interval of at least 90 min before exercise and reducing by up to 80% seem to have the most significant impact on the risk of a hypoglycemic episodes and better post-workout control.

References:

1) Zaharieva DP, McGaugh S, Pooni R, Vienneau T, Ly T, Riddell MC. Improved open-loop glucose control with basal insulin reduction 90 minutes before aerobic exercise in patients with type 1 diabetes on continuous subcutaneous insulin infusion. Diabetes care. 2019;Dc182204:182204. doi:10.2337/dc18-2204

2)  Roy-Fleming A, Taleb N, Messier V, et al. Timing of insulin basal rate reduction to reduce hypoglycemia during late postprandial exercise in adults with type 1 diabetes using insulin pump therapy: a randomized crossover trial. Diabetes & metabolism. 2018;2018 Aug 27. doi:10.1016/j.diabet.2018.08.002