If you're planning to exercise for a long time - half a day or more - you can take less insulin to prevent low blood sugar instead of eating extra food. This is especially convenient if you can't stop to eat during the activity. Here are some guidelines to help you figure out how to decrease your insulin dose.

• Decide which insulin is working hardest during the time you will be exercising.
  • The morning dose of regular insulin works hardest between breakfast and lunch.
  • The morning dose of NPH works hardest between lunch and dinner.
  • The dinner dose of lispro insulin works hardest between dinner and bedtime.
  • The bedtime dose of NPH works hardest during the night.
• Decrease that insulin dose by 10% of your total daily insulin dose.

For example, if your daily dose is 6 units of regular insulin plus 24 units NPH before breakfast, 4 units of lispro at dinner, and 6 units of NPH before bedtime, then your total daily dose is 40 units. If you are going for a morning hike, you will decrease your morning dose of regular insulin by 4 units (taking 2 instead of 6). If you have baseball practice in the afternoon, you will decrease your morning dose of NPH by 4 units.

Check with your healthcare team before making such dose changes. Doing so can help to prevent hypoglycemia.

Related information: Treatment - Insulin | Lifestyle - Exercise