I coach a college cross country athlete who has type 1 diabetes. He just can’t finish strongly at the end of a hard workout and races. Based on his workouts, he should be running faster. After the races his blood sugar level is 250-300 mg/dl [13.8-16.7 mmol/L] whereas before them, it is in the normal range. The ability to process the sugar seems like it might be the limiting factor and creating the tiredness at the end of the race. Any thoughts on solving this problem?

In someone who does not have diabetes, we don’t see this excessive rise in blood sugar as a result of intense exercise because of the precise, matching rise in insulin levels when needed. These rising insulin levels not only increase the utilization of glucose but also control the release of liver glycogen (stored glucose). So, it is not just the ability to process the sugar that is affected. The rise in glucose levels from liver sources, as a result of inappropriate levels of circulating insulin is also playing a role.

The difficulty in trying to accomplish this precise control in the athlete with diabetes is that we increase the risk of exercise-induced hypoglycemia. High intensity, anaerobic type exercise may require increased basal insulin. On an insulin pump, this can be addressed via a higher temporary basal rate surrounding exercise. On insulin injections, this may be a bit more difficult to accomplish. Some athletes in this situation do well with ingestion of a snack and appropriate rapid acting insulin coverage for that snack prior to exercise. The additional circulating insulin may help to minimize the liver’s release of glycogen, as well as assist in utilization of glucose during and immediately after exercise.

Athletes with diabetes should not attempt to do this without the assistance of their healthcare team, and certainly not before extensive blood sugar patterning indicates a consistent and predictable rise in blood glucose levels as a result of intense exercise. It is also important to recognize that, over time, training can result in adaptations which may change the blood glucose response to exercise. Frequent blood glucose testing and plans to address both hypo and hyperglycemia will need to be a part of the treatment plan.

The diabetes care team might also consider more extensive patterning of blood sugars during activity and training using The Continuous Glucose Monitoring System. Your student should talk to his diabetes care team about such options.

DMW