Effects of exercise on blood glucose

Exercise-related lows

If you take insulin or a sulfonylurea pill, exercise can lead to a low blood glucose level. Too much insulin in your system or too little glucose in your system from carbohydrate results in low blood glucose.

It is important you eat enough carbohydrate before and during exercise to help prevent low blood glucose. You may experience a low blood glucose level up to 15 hours after you stop exercising, because:

• exercise makes your body more sensitive to insulin, so your body uses glucose more efficiently
• your body pulls glucose out of your bloodstream after exercise to rebuild a store of glucose in your liver and muscles

Exercise-related highs

If you have type 1 diabetes, do not start exercising when your blood glucose level is more than 250 mg/dL. A high level indicates you do not have enough insulin in your system. If you exercise, there is a good chance your blood glucose level will go even higher due to stress hormones.

"Stress" hormones produce the "flight or fight" response. They stimulate the liver to release an extra burst of glucose — energy — to help the body meet the demand placed on it. In prehistoric times, a saber-toothed tiger may have triggered this demand. Today, it is more likely a self-inflicted demand. High-intensity exercise, illness or a tough day at work can cause stress.

Sometimes, the stress-hormone response causes a burst of glucose that overwhelms the insulin supply (natural or injected). The result is a temporarily high blood glucose level. This can happen during heavy, sporadic work (such as shoveling dirt or snow) or during an hour or more of exercise. Your stress hormones also can kick in if you are exercising vigorously, exercising too hard for your fitness level or if you are in a competitive situation.

Here is what happens:

1. Sporadic, heavy work
2. Stress hormones produced
3. Liver releases burst of glucose
4. High blood glucose may result

Once your body has enough insulin (injected or natural), your blood glucose level will come down. But exercising before it does can complicate your overall blood glucose control. It is best to wait until your level is below 250 mg/dL. High blood glucose can lead to the dangerous buildup of ketones in the blood and urine.

For more information, call International Diabetes Center at 952-993-3393 or toll-free at 888-825-6315.