Delayed response to an injection of U-500 regular insulin is not rare.

Highlights Since the PK/PD of U-500 regular insulin more closely resembles that of NPH insulin, it is commonly given before breakfast and dinner. However, a delayed response in which the major effect of the concentrated insulin takes place overnight occurs in about 10% of patients. This necessitates converting the regimen to a basal/bolus one in which the before breakfast injection serves as the basal insulin and short- or rapid-acting insulin is given before meals to control daytime hyperglycemia.