Is it better to reduce basal insulin rate or remove insulin pump before exercise in type 1 diabetes?

The aim of this study was to investigate if reducing basal insulin rate (BRR) 90-minutes before exercise was better at preventing hypoglycemia (dangerously low blood glucose) than suspending the insulin pump (pump suspension; PS) in type 1 diabetes (T1D). The main finding was that BRR 90-minutes before exercise improved blood glucose control and reduced hypoglycemia compared to PS.

Insulin is the treatment for type 1 diabetes (T1D). It is a hormone that lowers blood glucose. Insulin treatment is made up of basal insulin and mealtime insulin. Basal insulin controls blood glucose between meals. Mealtime insulin controls blood glucose after meals. Insulin can be delivered continuously through a pump that is controlled by the patient (open-loop insulin pump).

Exercise is an important part of T1D treatment. It lowers the risk of heart disease and improves overall wellbeing. However, during exercise, the body uses more glucose. Therefore, patients must take actions to prevent blood glucose from going too low (hypoglycemia). These actions include: eating more carbohydrates, reducing basal insulin rate (BRR) before exercise or disconnecting their insulin pump during exercise (PS). It is not known if BRR or PS is better at controlling blood sugar after exercise in T1D.

This study included 17 patients that had T1D and an open-loop insulin pump. Patients completed three 60-minute treadmill exercise sessions. During the first session patients removed their pump when they began exercise. For the second session, patients reduced their basal insulin by 80% 90-minutes before exercise. For the third session, they reduced their basal insulin by 50% 90-minutes before exercise.

Blood glucose level was significantly higher with BRR 50% at the start of exercise. At the end of exercise, BRR 80% had the smallest drop in blood glucose levels (-31 mg/dL) compared to 50% BRR (-47 mg/dL) and PS (-67 mg/dL). With PS group, 7 out of the 17 patients developed hypoglycemia compared to only 1 out of 17 with both BRR. After a standard meal post-exercise, blood glucose rose with PS and 50% BRR but did not rise with 80% BRR.

The authors concluded that, compared to PS, 50-80% BRR 90-minutes before exercise, improves blood glucose control and reduces the risk of hypoglycemia. They also determined that it does not compromise post-exercise meal blood glucose control.

This study was funded by Insulet Canada Corporation and Insulet Corporation, the developers of insulin pumps. This study involved a very small number of patients. Larger studies are needed.

If you have any concerns about managing T1D, please consult with your doctor.