The best approach for reducing basal insulin on a pump for exercise is to plan in advance and do the basal rate reduction well before exercise starts.

Try this method for prolonged aerobic exercise (lasting at least 45 minutes):

• Reduce the basal insulin by 50% 90 minutes before exercise starts.
• Carefully monitor your blood sugar and next time, change the percentage reduction if you did not stay in target range (e.g. a little less of a reduction if glucose levels were too high, a little more of a reduction if levels were too low).
• How much to reduce the rate down by can be tricky, so it should be based on your previous exercise patterns!
• The reduced basal rate should remain reduced throughout the exercise and until roughly 90 minutes after the exercise is done. (This will be important in reducing your risk of lows.)

If you forget to do this, try reducing your basal rate by 80% at the onset of exercise. (This percentage will vary from person to person and as fitness changes.) If you are planning to suspend your pump start of exercise, then make sure it is for no longer than 2 hours as more than this increases the risk of ketones forming – something best avoided!

The Basal Adjustment method can be very useful if exercise is prolonged, specifically because insulin going into the body from a pump can take up to a few hours to actually start working.