The patient was 82-year-old man with type 1 diabetes mellitus. He had been using insulin degludec (IDeg) and insulin glulisine (IGlu) for treatment. He was admitted to our hospital due to diabetic ketoacidosis. As he started eating after recovery, we restarted intensive insulin therapy for glycemic control. Although he had eaten almost whole meals, his fasting blood glucose was extremely low, and the existence of nocturnal hypoglycemia was apparent. We reduced the dose and changed the injection time (evening→morning) of IDeg. We also stopped the evening IGlu injection; however, his nocturnal hypoglycemia did not improve. We decided to switch IDeg to insulin glargine U300 and to attach an intermittently scanned continuous glucose monitor (isCGM). His nocturnal hypoglycemia improved three days later. Since he had chronic heart failure and premature ventricular contractions, we used a Holter electrocardiogram to investigate the difference in arrythmia during hypoglycemia and non-hypoglycemia. As a result, the number of premature ventricular contractions was apparently high during hypoglycemia. In the present case, which involved an elderly patient with type 1 diabetes mellitus, chronic heart failure and nocturnal hypoglycemia, switching IDeg to insulin glargine U300 improved nocturnal hypoglycemia. IDeg differs from insulin glargine U300 in that it has a fatty acid side chain, which leads IDeg to combine with serum albumin. We thought that the increased level of free fatty acid due to hypoglycemia was competing against albumin combined IDeg, which increased free IDeg, and as a result, encouraged hypoglycemia.
Keywords: Arrythmia; Elderly people; Insulin degludec; Nocturnal hypoglycemia; Type 1 diabetes mellitus.