An intermediate-acting insulin used in the treatment of diabetes mellitus. Administered once or twice daily, NPH (neutral protamine hagedorn) insulin lowers blood glucose within 1 to 2 hours after administration and exerts a peak effect at 6 to 10 hours. Endogenous insulin, a pancreatic hormone composed of two polypeptide chains, is important in the normal metabolism of carbohydrates, proteins and fats, promoting glucose utilization and protein synthesis; it has anabolic effects on many types of tissues.