Home / Resources / Articles / Risk Associated with Insulin Dose Before Exercising

Risk Associated with Insulin Dose Before Exercising

Mar 30, 2021
Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Aleksandra Kusic, PharmD Candidate, Florida A&M University, College of Pharmacy and Pharmaceutical Sciences

A small pilot study investigates how modest hyperglycemia, not hyperinsulinemia, is better for people with type 1 diabetes during exercise.    

Physical activity is vital for people with diabetes to help maintain better control of their blood sugar levels and increase insulin sensitivity. Patients with diabetes should implement 150 minutes per week of moderate-intensity exercise.  Physical activity can contribute to variations in blood sugar levels depending on the exercise, duration, and many other factors. A small pilot study was conducted which showed that low insulin coupled with euglycemia or modest hyperglycemia is more favorable for people with type 1 diabetes during exercise. According to Rita Basu, MD, “Hyperinsulinemia, but not hyperglycemia, blunts compensatory exercise-induced increase in endogenous glucose production in type 1 diabetes.” People with type 1 diabetes will have higher insulin concentrations in the peripherical circulation, leading to blunt regulatory increase response of endogenous glucose release during exercise, which can cause an episode of hypoglycemia to occur. Acute hypoglycemia can be very dangerous and lead to hospitalizations for some patients.  


The pilot study wanted to distinguish the effects of hyperglycemia vs. hyperinsulinemia on exercise-induced increases in glucose disappearance and endogenous glucose production in patients with type 1 diabetes. The study was conducted with six participants with type 1 diabetes using insulin pump therapy and six without diabetes to analyze the effects of euglycemia with low insulin, euglycemia with high insulin, and hyperglycemia with low insulin during the three scheduled visits.  The glucose fluxes were measured using (6,6-2H2) glucose test before, during, and 60 minutes after exercise. All participants were matched for age, fat-free mass measured via DXA, and VO2 max levels of 65% were set as moderate activity by the researchers.   

Results from this study showed that all participants had an increased rate of glucose disappearance with exercise (P< 0.01), but the peak rate of glucose disappearance during exercise was lower for type 1 diabetic participants (P<0.01) during all visits. Increased rate of glucose disappearance can cause the patient with diabetes to develop low blood sugar during and after exercise. For patients with type 1 diabetes, the endogenous glucose production increased (P<0.001) with exercise during low insulin and euglycemia or hyperglycemia, but not during euglycemia with high insulin. Therefore, it is favorable for the patient to have euglycemia or hyperglycemia with low insulin because endogenous glucose production is vital when exercising. Modest hyperglycemia or euglycemia will provide the patient with the glucose that the muscles will use to perform functions without causing an acute drop in glucose levels during the exercise. If the patient has hyperinsulinemia before exercise due to the insulin dose, the patient will be at a higher risk of developing low blood sugar during the exercise. 

Exercise-induced hyperinsulinemic hypoglycemia occurs by blunt compensatory exercise-induced increase in endogenous glucose production in people with type 1 diabetes. Hypoglycemia is a dangerous acute adverse event that can occur if there is sufficient insulin and insufficient glucose to balance it. Thus, exercising shortly after taking insulin dose can be unsafe because of the abundance of insulin, but not enough glucose to exercise and still be able to maintain a healthy blood glucose level. Also, bolus and rapid-acting insulin cause quick drop in glucose, increasing the patients’ chance of developing hypoglycemia if not carefully monitored. People with diabetes may have to eat carbohydrates and decrease their insulin dose before exercise to avoid experiencing hypoglycemia.  

While exercising, it is beneficial for people with type 1 diabetes to closely monitor blood glucose before, during, and after exercise to determine how glucose levels are impacted by the different activities performed. People with diabetes benefit from euglycemia or modest hyperglycemia during exercise because the body needs additional glucose for the muscles to function without causing a significant drop in blood glucose. Self-monitoring for glucose blood levels is vital to avoid hypoglycemia caused by hyperinsulinemia for people with diabetes. Decreasing insulin dose before exercising can be beneficial to sustain an average glucose level during and after exercise. 

The small pilot study suggests that modest hyperglycemia, not hyperinsulinemia, is more beneficial for people with type1 diabetes when exercising. Howeever, there needs to be a larger cohort of diabetes patient participants with a wide range of exercise intensities and activities for the results to be more specific rather than a general outlook. Patients with diabetes should continuously monitor their blood glucose levels throughout the day to detect how physical activities can affect their glucose levels. 

Practice Pearls: 

  • Patients with type 1 diabetes should check their glucose levels before, during, and after exercise to see how their exercise routine affects their blood glucose levels.  
  • Normal or modestly elevated blood glucose levels are favorable during exercise for patients with type 1 diabetes.  
  • Exercising shortly after insulin dose can be dangerous because hyperinsulinemia, not hyperglycemia, blunts compensatory exercise-induced increase in endogenous glucose production in type 1 diabetes. 


Romeres, Davide, et al. “Hyperglycemia But Not Hyperinsulinemia Is Favorable for Exercise in Type 1 Diabetes: A Pilot Study.” Diabetes Care, 2020, doi:10.2337/dc20-0611. 


Aleksandra Kusic, PharmD Candidate, Florida A&M University, College of Pharmacy and Pharmaceutical Sciences