I swim for an hour in the morning. I can start with a 80-90 mg/dl [4.4-5 mmol/L] blood sugar (I monitor it every 15 minutes or so), and I am fine when I get out of the pool, but my blood sugar continues to rise. I will bolus for the amount missed while in the pool and possibly more, yet my blood sugar continues to go up (200-250 mg/dl [11.1-13.8 mmol/L]). Some days, if my blood sugar is 100-120 mg/dl [5.6-6.7 mmol/L], I bolus one-half the amount that I will miss while off the pump before I go in, then the rest afterward. If I don’t exercise, I have tested my basal rate, and I can maintain my blood sugar level without eating. It is so frustrating to exercise, and then have my blood sugars go way up. I was swimming in the evening but was having the same problem. My doctor thought that I would have better luck in the morning before eating, but it hasn’t helped.

You are not alone in your frustrations regarding elevated blood sugars after intense exercise. Research in subjects (who do not have diabetes) during and immediately after higher intensity exercise demonstrated increases in circulating insulin levels to compensate for the liver glycogen release that is a physiologic response to intense exercise. It may be that the rise that you are experiencing is two-fold: related to both the fact that your basal insulin during exercise has been reduced as a result of disconnecting the pump during your water workout; and this need for increased basal insulin post exercise. It is possible that, despite the fact that you bolus, to cover for the rise, the absorption rate of this bolus is not matching the liver glycogen (and hence basal insulin) need.

This brings to mind two questions: First, what would your post exercise blood sugars look like if you wore the pump at your normal basal rate during your workout? Second, it is obviously more convenient to take the insulin pump off during your water workout, would you be able to control that rise with a combination of a bolus prior to disconnecting (to cover for that missed basal), and an elevated temporary basal rate upon reconnection post exercise? These are a few options you may wish to discuss with your diabetes team.

DMW