Managing Blood Sugar During Physical Activity
Physical activity lowers blood sugar, right? Actually, it’s not quite that simple, especially for people with type 1 diabetes.
In reality, blood sugar can go up or down during and even after physical activity. Everyone’s body responds a little differently, but in general:
- Low blood sugar (hypoglycemia) from physical activity most often happens to people with type 1 diabetes who exercise for long periods or who work out hard without adjusting their insulin dose or meal plan
- High blood sugar (hyperglycemia) can happen to people who perform very high-intensity (anaerobic) exercise
It’s not always possible to know how your blood sugar is going to react to different activities. Some change is unavoidable, but the key is to keep your blood sugar levels from going too high or too low. This isn’t always easy and everyone’s body responds a little differently to physical activity. But monitoring blood sugar before, during, and after physical activity reveals a pattern of how certain activities affect your blood sugar levels.
Avoiding lows during and after physical activity
- Be mindful of length of time. Blood sugar levels can go too low if you engage in physical activity for long periods
- Eat something first. Engaging in physical activity on an empty stomach can cause low blood sugar
- Plan for your insulin and food needs. This may take some trial and error as well as the help of your diabetes care team. But adjusting the insulin dose and food intake to the level of physical activity you plan to be doing can help keep your blood sugar in a safe range
- Stop if you feel any warning signs of hypoglycemia. Just going “5 minutes more” can be dangerous. Take a moment to eat or drink some kind of high-carbohydrate food if you feel like you are going low
- Keep “emergency carbs” close at hand. Always keep some form of high-sugar food handy. This can be a soft drink (nondiet), fruit juice, glucose tablets, raisins, or hard candy
- Monitor later, too. Blood sugar levels can drop even 16 to 24 hours after physical activity because the body uses blood sugar to replace sugar that has been used by the muscles
Avoiding highs during and after physical activity
- Make sure not to start out too high! A high blood sugar level can rise even higher because of exercise
- Match insulin dose to activity intensity. Blood sugar levels can also go too high if physical activity is too intense and/or insulin levels are too low. What happens is the nerves signal the liver to release stored glucose, which can cause a rapid rise in your blood sugar levels
- Check for ketones. If blood sugar is too high, the body might produce ketones (acidic waste products that can occur when fat is broken down for energy), and a dangerous condition called ketoacidosis can result. Check blood sugar before and after exercising to avoid high blood sugar and, if your blood sugar is unusually high for you, check for ketones, too!
- Going for the long haul? You may need to eat during or after physical activity if the workout is very intense or continues for a long time. A low-fat snack that has 15 to 30 grams of carbs may help. Repeat this snack based on blood sugar levels
Know which way your blood sugar is going!
Before starting physical activity, it’s helpful to know which way your blood sugar level is heading. Start checking 90 minutes before starting an activity. If checks show that your blood sugar level is going down (even if it is still in a safe range), a snack may keep it from going any lower. This is particularly important if you are about to start an activity where it is difficult or inconvenient to stop and check your blood sugar in the middle of doing it.