Glucagon is a 29 amino acid peptide produced by the alpha cells in the pancreas. It is produced by proconvertase 2 processing products of the pre-pro-glucagon gene. Classically hypoglycaemia triggers glucagon release. Hypoglycaemia is sensed within the hypothalamus, particularly the ventromedial hypothalamic nucleus, and the parasympathetic nervous system relays the signal to the pancreas to cause glucagon release. Glucagon release is inhibited by hyperglycaemia, insulin, GLP-1 and somatostatin. The main function of glucagon is to increase blood glucose, through both glycogenolysis and increased gluconeogenesis. It also affects lipid metabolism, breaking down fat through lipolysis and increasing ketone production. Glucagon affects protein metabolism, increasingureagenesis and causing amino acid uptake into hepatocytes. The resultant carbon skeletons can then enter the gluconeogenic pathway. Glucagon therefore acts in multiple ways to maintain fuel supply to all organs in the body.