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Answers from the BJC Experts

Ask the BJC Expert allows you to get the answers you need about a variety of health, medicine and exercise issues to help you live a more healthy life.

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My blood glucose levels two hours after I eat are usually back into the 80s or 90s and my levels have only been high a couple times, usually after eating a lot of sugar or carbs. But when I work out my levels drop into the 60s from 100 quickly. What is going on?

I don’t know if you have diabetes or not, and if you are type 1 or 2. That does make a difference here, but I will answer the best I can. When we exercise, our muscle cells need quick energy. We use the available glucose (sugar) in our blood and the stored sugar (glycogen) in our muscle cells first. Then, we convert stored glycogen in our liver into sugar. After about 30 minutes of exercise, our stores are depleted and we have to rely on free fatty acids. Exercise demands fuel (sugar). Blood glucose levels can drop rather quickly.
Since you know your response to exercise, testing before exercise is crucial. If blood glucose is less than 100 mg/dl, you need to have 15 grams of carbohydrate. If exercising for an hour or more, you may need 30 grams of carbohydrate. If it has been several hours since a meal, add protein to the snack.
If you have diabetes and are trying to lose weight, discuss with your doctor about reducing the dose of your medications on the days you exercise. That can help prevent hypoglycemia(low blood sugar). Some people experience low blood sugar for several hours after exercise. You may need carbohydrate snack immediately following exercise. Glycogen stores can take up to 24 hours to replenish.

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