Insulin is the main hormone, a polypeptide, that regulates uptake of glucose into cells (primarily muscle and fat cells) from the blood. Insulin is released in the beta cells of the islet of Langerhans in the pancreas, the gland that lies just behind the stomach.

Normal insulin production in the pancreas is released in two different ways, basal and meal-stimulated. Basal insulin secretion refers to a constant release of a certain small amount of insulin by the pancreas.

This helps your body get the fuel needed for different activities you perform throughout the day. Pulsatile insulin secretion occurs after a meal and helps you body metabolize the food you eat. This allows glucose and other nutrients to reach the cells to be used to produce energy or to be stored as fat. Every time blood glucose concentrations are over 100 mg per dL, insulin secretion increases. When insulin levels are high, the liver stops producing glucose and stores it in other forms until the body needs it again. As blood glucose level reduces after reaching their peak, the pancreas reduces the production of insulin. About two to four hours after a meal both blood glucose and insulin are at low levels, with insulin being slightly higher. The blood glucose levels are then referred to as fasting blood glucose concentrations.