Carbohydrate Adjustments for Exercisers with Diabetes

Many people with diabetes have special needs that should be considered when planning an exercise program.

Exercise can cause your blood glucose levels to drop too much, especially if you take insulin or other glucose-lowering medications. Symptoms of hypoglycemia, or "low blood sugar," include feeling shaky, lightheaded, weak, confused, anxious, fatigued, irritable, or hungry, headache, breaking out into a clammy sweat, or even fainting.

Hypoglycemia can happen during exercise, right after exercise, or even up to 24 hours after you finish exercising. Symptoms of hypoglycemia can be mild and gradual; but it is more common that symptoms come on very quickly. By paying close attention to how you’re feeling, you can prevent problems before they put you at risk of injury.

Because of the risk of hypoglycemia, you should always check your blood glucose level before you exercise. Having a carbohydrate containing snack prior to exercising is one way to prevent exercise related hypoglycemia. Use the chart below to make the recommended adjustments, based on your glucose reading, before you exercise. Click here for a detailed, printable chart that shows single (15-gram) servings of carbohydrate-containing foods.

Adjustments Based on Blood Glucose Levels Before Exercise
Exercise Duration & Intensity <100 mg/dL 100-180 mg/dL 180-250 mg/dL
< 30 min. at low intensity Eat 15 g carbohydrate N/A N/A
30-60 min. at moderate intensity Eat 15 g carbohydrate 100-120: Eat 15 g carbohydrate. 121-180: N/A N/A
30-60 min. at high intensity Eat 30 g carbohydrate Eat 15 g carbohydrate N/A
> 60 minutes at moderate intensity* Eat 15 g carbohydrate per hour of activity Eat 15 g of carbohydrate per hour of activity After 1 hour of activity, eat 15 grams carbohydrate
  • Examples of low-intensity exercise: yoga, leisurely walking or biking
  • Examples of moderate-intensity exercise: vigorous walking, swimming, tennis
  • Examples of high-intensity exercise: running, Spinning, aerobics or kickboxing
  • Examples of long-duration (60+ minutes) moderate-intensity exercise:team sports, golfing, cycling or swimming
*Retest your blood glucose after each hour of activity and follow recommendations based on your reading. Contact your physician if you experience symptoms of hypoglycemia during or after exercise for 2 or more consecutive days.

For more specific information or help, talk to your health care provider. The American Diabetes Association's National Call Center also offers live advice from 8:30 a.m. to 8 p.m. EST, Monday through Friday at 1-800-DIABETES or 1-800-342-2383.

This article has been reviewed and approved by Amy Poetker, Registered Dietitian and Certified Diabetes Educator.
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About The Author

Becky Hand
Becky Hand
Becky is a registered and licensed dietitian with almost 20 years of experience. A certified health coach through the Cooper Institute with a master's degree in health education, she makes nutrition principles practical, easy-to-apply and fun. See all of Becky's articles.