Diabetes Forecast

How Do I Fuel for Exercise?

I have type 2 diabetes, and I am a runner. Every day I run for 1 hour. What food can I eat, and what should I drink before I run? Miguel Ángel Sosa Alfonso, Colombia, South America

Meghann Moore, RD, CDE, MPH, responds

It is not usually necessary to eat extra for activities lasting an hour or less, but depending on the intensity of exercise you do, how long you work out, and the type of medications you’re on, you may need to fuel up before, during, or after a workout.

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To best determine if you need to eat, consider the intensity of the run and check your blood glucose at the start and end of your workout. For example, if your blood glucose typically drops 50 mg/dl during a run and your target blood glucose is 120 mg/dl, you would want to eat a snack when your pre-run blood glucose readings are less than 170 mg/dl. If your pre-run blood glucose is 200 mg/dl, however, you probably don’t need a snack.

If you take insulin or certain oral medications—such as glyburide, glimepiride, or glipizide—you may be at a higher risk for exercise-induced hypoglycemia (low blood glucose). In that case, eat a snack with 10 to 20 grams of carbohydrate for every 30 minutes of moderate exercise (when you can hold a conversation while working out, but can’t sing). Five to 10 grams of carbohydrate should be adequate for a low-intensity run (when you can comfortably sing a tune while you exercise). Still, you may need extra carbs during or after your workout to keep your blood glucose from dipping too low.

Good choices for a pre-run snack include slowly absorbed carbohydrate sources, such as whole grain snack bars, apples, peaches, dates, figs, milk, and yogurt. If you use sports drinks, which raise blood glucose quickly, consider those with 6 to 8 grams of carbohydrate per 100 milliliters of fluid.

Water is generally enough to keep you hydrated for an hour-long run. Weigh yourself before and after the run, then drink enough water to equal the weight you lost. (Hint: 4 cups of water weighs 2.2 pounds.)


Eating a moderate amount of carbohydrate-containing food before a run is recommended to prevent low blood glucose. Check your blood glucose right before and directly after the run to determine how much you need.



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