Adjusting Basal Insulin on Injections - ExCarbs

Adjusting
Basal Insulin
on Injections

Why is it sometimes important to adjust your basal (long-acting background) insulin before or after exercise if you are on a long acting or intermediate acting insulin?

This is necessary to reduce your risk of late lows after aerobic exercise; it will also depend on which basal (long-acting background) insulin you are using. Best to talk to your diabetes team if you are using insulin injections!

It can get a little tricky if you are taking long acting insulin injections.

Remember: If you have already had an injection, you cannot get that insulin back out, so it will continue to work even when you are exercising. In these cases, it is important to have ExCarbs handy.

If exercise happens every day then it is possible you can reduce your basal dose by about 20% to account for this increased insulin sensitivity with exercise, but if for some reason there is a day you don’t exercise, your sugars are likely to run a bit higher than you would anticipate.

If exercise is planned for just a couple of days a week then it is possible you can reduce your long acting insulin the night before, but this does potentially leave a risk of your blood sugar getting higher later in the day or the next morning.

There are several ways to get around this:

  • Try splitting your dose so it is taken twice a day which will allow the dose to be reduced either before or after exercise. This should first be discussed with your diabetes specialist team.
  • With the permission of your diabetes specialist team, consider pump therapy.
  • Think about using a differing insulin such as NPH, while slightly older, doesn’t last as long, so can be taken twice daily. This also should first be discussed with your diabetes specialist team.
Here are more suggestions for adjusting basal insulin:
  • For prolonged aerobic exercise, lowering your dose by 20% before you start is useful if the exercise is frequent (less than every 3 days).
  • For brief aerobic or anaerobic exercise, best not to change the dose before. Sometimes this needs to be increased if blood sugar levels start to rise.
  • After exercise, try a 20% lower nighttime dose (injection) to prevent night time lows.
  • At the end of exercise a short sprint can also lower the later risk of a low for some people.