I have read that someone with type 1 diabetes taking more exercise than usual can take less insulin or should eat more carbohydrate. If insulin is used to get glucose into the body’s cells, why should more activity require less insulin? Is insulin sometimes required twice (being used to store carbohydrate currently not wanted in the liver)?

Exercise allows insulin to work more efficiently by changing insulin receptor activity on the cell surface — including the muscle cell. Thus, more exercise/activity, less insulin needed to do the job of allowing glucose to enter the cell. Therefore, more food or less insulin is needed to keep glucose levels steady with activity.

A key problem is figuring out when this change occurs. Most advice is too simplistic and merely says take more food or take less insulin. In fact, one needs to decide whether this should be during the activity, just after the activity, or for hours later. This is very individualized and also changes with intensity and duration of activity, whether the activity is truly aerobic or not and idiosyncratic factors. Frequent blood glucose testing usually can help define what occurs for any individual. Working with your diabetes team can help you figure out ways to respond to activity.

SB