U-500 regular insulin in automated insulin delivery systems for severe insulin resistance: A single-center retrospective cohort.

U-500 regular insulin use in automated insulin delivery systems (AIDs) is off-label and minimally studied. In this four-individual cohort, HbA1c remained stable, time below range stayed low, and no diabetic ketoacidosis or severe hypoglycemia occurred, despite lower TIR. These findings provide early clinical experience to inform cautious, individualized off-label use.