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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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Member Comments

If this is for T1 diabetics then I cannot comment BUT for me as a T2, 100mg/dL is quite a normal reading, usually around 85 to 90 is good for me so why would I want to eat carbs to bump it up. If I was at 100 t0 180 I would be very upset and not eat for quite a while and if I was 180-250 it would be increasing my insulin not my carbs. You also dont say what type of carbs - please dont tell people to eat white starchy carbs as they are like giving an alcoholic more booze - just makes the condition worse. Please stop pushing carbs unless it is vegetable or fruit based. Report
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Good knowledge and article Report
I am a diabetic with my blood sugar in control, the average number now is 82. I check it 5-6 times a day because I am constantly experimenting with new foods , but more important I do various intense exercises and I want to learn the effects it has on my body from the different routines. it works for me. Report
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This would knock diabetics on keto or low carb diets out of their regime completely. It is worth considering, and everybody is different, but I could not take 15 g of carbohydrates before my hour of swimming and succeed in weight loss. Report
Helpful info. Hope someday to be back into moderate activity levels. Meanwhile I am prediabetic, taking 750mg of Metformin ER once daily. Very conscious of diet & ltd exercise due to chronic back issues. Down 30 lbs w/ more to lose. Really rely on SP to help me w/ tracking & motivation. Report
Actually having a low sugar today. I was good and checked before getting on treadmill. It was 63. I ate like I normally do everyday. I have been exercising 30 to 35 minutes a day on treadmill. Today I will go over calories because of trying to get sugar up. It doesn't seem to want to go up. Best I can do after eating 2 snack is 101. So I just ate diner. I had pasta and I never eat that because it always spikes my sugar. so far 108. I really want to exercise. I am trying to be patient, but bugging out. The pasta is not spiking it like normal either. it did go up a little. So I try again in 15 minutes and then will give treadmill a shot.

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I don't know if your publishers look at all the photos on articles that promote exercise and other healthy lifestyles, but of the 4 that were available to read after I tracked my food, this was the only one that showed a body in a sweat suit that had some extra "personal upholstery" on it. The other three showed thin athletic bodies in tank tops and shorts. I chose this article because of that. I got some good tips and will continue to pick the articles with photos of people who are not perfectly sculpted over those that are. Report
Good article. Report
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Have my diabetes under control, but it is still a struggle to make sure it stays that way. Report
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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.