Insulin Edema With Use of U-500 Regular Insulin in a Hybrid Closed-Loop Insulin Pump

Insulin edema is a rare complication of insulin therapy which has been described in known or newly diagnosed people with diabetes, following initiation or intensification of insulin treatment. Here we present a 63-year-old man with complaints of weight gain, shortness of breath, and lower extremity edema starting two weeks after the change of his insulin pump to the hybrid closed-loop insulin pump system and substitution of U-100 aspart insulin with U-500 regular insulin. Laboratory studies, imaging, and electrocardiogram (EKG) were performed to evaluate the cause of acute edema and were all normal. Hemoglobin A1C showed remarkable improvement after the pump change and the insulin pump download showed a significant increase in the amount of total daily insulin administered. With the exclusion of other causes of acute edema, the patient was diagnosed with insulin edema. He was started on spironolactone 50 mg/daily and showed a desirable improvement of edema on follow-up.  This case shows that although the use of the hybrid insulin-pump system helps to obtain better control of diabetes in many patients, the rapid improvement in glycemic control may precipitate the development of insulin edema. Furthermore, the use of high concentration insulin in insulin pumps is off-label and their use might increase the rate of complications of insulin therapy including insulin edema.