Your blood glucose response to exercise will vary depending on:
- your blood glucose level before starting activity,
- the intensity of the activity,
- the length of time you are active,
- and changes you’ve made to insulin doses.
Sometimes people experience a drop in blood glucose during or after exercise, so it is very important to monitor your blood glucose, take proper precautions, and be prepared to treat hypoglycemia (low blood glucose).
To learn how different types of activity affect you, you should frequently check your blood glucose before, during, and after an exercise session.
Put a trial and error system into place. For example, increased activity may mean that you need to lower your insulin dose or eat some extra carbohydrates before exercising to keep your blood glucose in a safe range. Some activities may cause your blood glucose to drop quickly while others do not.
If your blood glucose levels are trending down before a workout, have a pre-exercise snack. Always carry a carbohydrate food or drink (like juice or glucose tabs) that will quickly raise your blood glucose. It may take a while to figure out what works best for you.
If your blood glucose level is less than 100 mg/dl before you start your activity, try having a small carbohydrate snack (about 15 grams) to increase your blood glucose and reduce your risk for hypoglycemia. This is especially important if you anticipate that your body’s circulating insulin levels will be higher during the time you exercise and if you will be exercising for longer than 30 minutes.
If you use an insulin pump, you may be able to avoid adding an extra snack by lowering your basal insulin rate during the activity.
If you have repeated problems with your blood glucose dropping during or after exercise, consult your doctor.