Fueling for Exercise with Insulin Use

Experts recommend at least 150-minute weekly of moderate physical activity for all adults.1 Exercise is a key part of diabetes self-management. When you are using insulin there are important factors to consider when thinking about exercise.  

Before beginning any exercise, make sure you test your blood sugar about 15-30 minutes prior. If your blood sugar is between 100-250, you are good to go. Anything lower, eat a small snack containing 15-30 grams of carbohydrates. This will help your blood sugar levels stay consistent during your workout.3 Carbohydrates are a recommended pre-workout snack, as they are shown to enhance performance and prevent your body from depleting your glucose stores.4 However, with normal or elevated blood sugar, a pre-exercise snack is not necessary.   

During exercise, it is necessary to self-monitor symptoms. Values should be greater than 70 mg/dL,if they are not  stop exercising immediately and check your blood sugar.3. If it’s less than 70 mg/dL, utilize approximately 15 grams of fast acting carbohydrates.3 Some examples are ½ cup of fruit juice or regular soft drink or glucose tablets. Wait at least 15 minutes and recheck blood sugar. If it’s over 70 mg/dL, you can return to exercise.  

Following exercise, continue to monitor your blood sugar levels and symptoms, as hypoglycemia (low blood glucose) can occur four to six hours following an exercise session. The longer you participate in the exercise, the longer your blood sugar can be affected.3 Exercise draws on your stored glucose within your body, which draws from glucose in your blood to replenish stores leading to hypoglycemia. If low blood sugar occurs, eat a small snack of carbohydrates (i.e., fruit, crackers, glucose chews) or a half cup of fruit juice. Additionally, consuming a meal or snack with at least 20 grams of protein will help to build muscle.5 In addition to benefiting glycemic control, physical activity also decreases risk of heart disease and stroke over time.3 Overall, exercise has a variety of benefits for individuals, regardless of the progression of diabetes.  

Your hemoglobin A1c (HbA1c) shows how well blood glucose levels were managed over the past 3 months.  Regular physical activity over 8 weeks or longer has been shown to improve HgbA1c levels in many people. Larger improvements have been seen with strenuous exercise, making it a key component of blood sugar control.2   



1. Piercy KL, Troiano RP. Physical Activity Guidelines for Americans From the US Department of Health and Human Services. Circulation Cardiovascular quality and outcomes. 2018;11(11). doi:10.1161/CIRCOUTCOMES.118.005263 

2. Fowler MJ. Diabetes treatment, part 1: Diet and exercise. Clinical Diabetes. 2007;25(3). doi:10.2337/diaclin.25.3.105 

3. Mayo Clinic Staff. Diabetes and Exercise: When to monitor your blood sugar. Mayo Clinic. 

4. Ormsbee MJ, Bach CW, Baur DA. Pre-exercise nutrition: The role of macronutrients, modified starches and supplements on metabolism and endurance performance. Nutrients. 2014;6(5). doi:10.3390/nu6051782 

5. van Loon LJC. Role of dietary protein in post-exercise muscle reconditioning. Nestle Nutrition Institute Workshop Series. 2013;75. doi:10.1159/000345821