Glucagon is a hormone secreted by the pancreas that increases the blood glucose level by stimulating the liver to change glycogen to glucose. It opposes the actions of insulin and is used to reverse hypoglycemic reactions and insulin shock. It prevents blood sugar from falling too low during periods between meals when glucose can easily be recovered from digestion of sugars and starches.
Patients suffering from hypoglycemia usually lack adequate production of glucagon and as a result their blood sugar tends to fall continuously if they do not eat.