A couple people have asked me why I reduce the basal rate on my insulin pump when I exercise.

I thought I better write a few paragraphs on the subject to help clarify.

A basal rate is the amount of insulin delivered during a single day (see also this definition). With my basal rates set correctly, I could go 24 hours without eating and my blood sugars would be within the normal range (i.e., 80-120 mg/dl) the whole time. I say basal rates (plural) because my basal rate isn’t the same all day long. Everybody is different, of course, but for me, I have a single basal rate for 8 AM to 10 PM and then another basal rate for 10 PM to 8 AM. Other people with diabetes might have more or fewer rate changes throughout the day, but between 2 and 5 different rates during 24 hour period is fairly common.

With aerobic exercise, insulin usage is more efficient, so my body needs less insulin. To keep my blood sugars within normal ranges during exercise, I have a few choices. First, I can lower my basal rate so that my blood sugar stays normal during exercise. This is a difficult approach because on just about any bicycle ride, the intensity varies widely. Plus, not eating anything during a long ride would leave my energy stores completely depleted and that’s not a good thing when you have to get up the next day and do another ride. A second approach is to leave my basal rates at their normal levels and keep my blood sugars normal by eating or drinking extra carbohydrates. This approach is difficult because it would mean carrying a lot of extra food with me everytime I ride. A third approach is simply a combination of the previous two approaches and it is the approach that I use. It allows me to eat while I’m riding to keep my energy stores up, but I don’t have to eat so much that carrying all the extra food is burdensome.

The trick, of course, is to know how much to lower the basal rate. Well, through experimentation, I’ve found that lowering my basal rate to 70% of it’s normal level gives me a good balance of a reduced basal rate and still being able to eat and drink carbohydrates during a ride. Depending on the intensity level of the excercise, I might lower my basal rate by just 10% for something easy (like a recovery ride) and by 50% for something really hard.

I hope this helps. If you have questions, leave a comment here or send me an email.

This entry was posted on Sunday, May 21st, 2006 at 7:07 pm and is filed under Diabetes, Exercise. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.