Insulin is a hormone that lowers the amount of glucose, or sugar, in the blood. A low level of insulin always exists in the bloodstream, but the pancreas secretes more after a meal is eaten. Insulin is made and secreted in the islet beta cells of the pancreas.
Insulin decreases blood glucose levels by stimulating fat, muscle and red blood cells to take in glucose from the blood.
Blood glucose levels are measured in milligrams per deciliter, or mg/dL. Normal levels of blood glucose lie between 70 mg/dl and 100 mg/dl. If blood glucose levels rise significantly above 100 mg/dl, then insulin is released from the pancreas. If glucose levels fall below 70 mg/dL, the secretion of insulin from the pancreas decreases.