Going low during exercise can be frightening. Preventing low blood glucose involves two strategies: decreasing insulin dosage or increasing carbohydrate intake. Sounds simple, but in reality it takes time for each individual to find the right combination that works for him or her.
Why decrease insulin and increase carbohydrate with exercise to prevent lows? Exercise causes an insulinlike effect; muscular contractions push glucose into the muscle—an action independent of insulin. So the normal dose of insulin when taken with exercise has the potential to trigger low blood glucose levels.
Preventing a Low
Here are some tips for preventing a low blood glucose during a workout. The goal is to complete your exercise and recovery with as little change in blood glucose as possible.
- Measure your blood glucose before exercise, and if it is below 90 mg/dl, extra carbohydrate may be necessary. If it’s between 90 mg/dl and 270 mg/ dl, no carbohydrate is needed. If blood glucose is above 270 mg/dl, delay exercising and measure the ketones in your urine. If ketones are negative, you can exercise, and extra carbohydrate is likely not needed. If ketones are positive, take insulin and don’t exercise until the ketones are negative. You should also monitor your blood glucose during and after exercise. You may need to include overnight monitoring if you were exercising later in the afternoon.
- Before your workout, consume about 15 grams of carbohydrate for every 30 minutes of anticipated moderate-intensity exercise. Some good choices are oatmeal cookies, dried fruit, granola bars and properly formulated sports drinks. You might eat additional carbohydrate after your workout, if needed.
- Take your reduced insulin dose about one hour before exercising (depending on peak action). Be sure to inject the insulin into tissue below the skin and not into muscle. The range for reducing your insulin dose before exercise is 25 to 80 percent, depending on your exercise intensity and duration. You’ll need to use trial and error and frequent monitoring to find what works best for you.
- No matter what you do, you might still experience a low with exercise. To prevent a serious emergency, be sure to carry some carbohydrate snacks with you. Have your medical identification handy, and try to exercise with a friend who is aware of your particular “low” symptoms and knows what to do if you should have a low.