Why does exercise sometimes raise my blood glucose?
Gary Schiener, MS, CDE, responds
Exercise is vital for everyone with diabetes. Being active most days of the week helps reduce long-term health risks, improves insulin sensitivity, and enhances mood and overall quality of life. Most of the time, working out causes blood glucose to dip. But certain types of exercise can cause your levels to rise during or after exercise. There are steps you can take to avoid this.
What to Know
Using your muscles helps burn glucose and improves the way insulin works. That’s why blood glucose levels usually come down during exercise. But you might see blood glucose go up after exercise, too. Some workouts, such as heavy weight lifting, sprints, and competitive sports, cause the production of stress hormones (such as adrenaline). These, in turn, raise blood glucose levels by stimulating the release of glucose by the liver.
The food you eat before or during a workout may also contribute to a glucose rise. Eat too many carbs before exercising, and your sweat session may not be enough to keep your blood glucose within your goal range.
Some people choose to accept a temporary exercise-induced glucose rise, knowing that the benefits of exercise far outweigh the drawbacks. But if you want to prevent the rise, here are some strategies that might help:
- Choose moderate-intensity aerobic workouts, or circuit weight training with light weights and high repetitions.
- Practice relaxation techniques such as paced breathing, visualization, or meditation before and during your workout to minimize the adrenaline effect.
- Consider moving your workout to later in the day if you usually exercise in the early mornings. The dawn phenomenon, a natural rise in blood glucose that occurs between about 4 and 8 a.m., can result in elevated levels during morning exercise. The same workout done later in the day is less likely to result in a rise.
- Talk with your physician about adjusting your rapid-acting insulin or other short-acting diabetes medications—meglitinides or amylin, for instance—prior to workout sessions that tend to produce a glucose rise.
- Avoid consuming excessive amounts of carbohydrate prior to and during your workouts. Instead, try some yogurt with nuts or peanut butter.
Physical activity is important for everyone with diabetes. Most forms of aerobic/cardiovascular exercise produce a drop in glucose levels, while activities such as high-intensity training and weight lifting can result in a rise. Managing glucose levels with any form of exercise is possible once you understand your personal patterns (doing regular blood glucose checks and keeping a workout log can help) and implement sensible adjustments.
Gary Scheiner, MS, CDE, is the owner and clinical director of Integrated Diabetes Services, a private practice offering individualized diabetes management consultations. He is a master’s-level exercise physiologist and author of six books, including Think Like A Pancreas. He’s had type 1 diabetes for 33 years and works out daily.