Human Glucagon is a peptide hormone. It is produced by the alpha cells of the pancreas and are responsible for increasing the glucose concentration in the bloodstream. The molecular weight of the polypeptide is of 3485 Daltons.  Human glucagon has an opposite effect to that of Insulin, which lowers the glucose concentration. Glucagon is released by the pancreas in cases where the concentration of glucose in bloodstream are low. Both Insulin and Glucagon are a part of feedback system which regulates the glucose level in the bloodstream. Glucose stored in liver is in the form of polysaccharide glycogen which is converted to glucose molecules by liver cells which consist of glucagon receptors. Glucagon turns off glycolysis which occurs in liver leading to shuttling of glycolytic intermediates towards gluconeogenesis. Glucagon is also associated with the induction of lipolysis. Production of glucagon depends on central nervous system pathways. 

Glucagon is used as an injectable as a first aid solution for severe hypoglycemia cases. This condition is when the individual is unable to take glucose orally. It is also used as a substitute of epinephrine in cases of anaphylaxis. Glucagon is known to act quickly and has side effects like nausea and headache. Glucagon binds to glucagon receptors, present in the plasma membrane and leads to conformation change which activates G proteins. Several cascading enzyme production leads to release of glucose molecules from the polymeric glycogen. Abnormally high levels of glucagon are indicative to pancreatic tumors like glucagonoma. This leads to symptoms like hyperglycemia, necrolytic migratory erythema and reduction in amino acids.