Glucagon, a peptide hormone derived from proglucagon in pancreatic α cells, regulates glucose metabolism. It stimulates glucose production in rat hepatocytes ex vivo and enhances glucose output from perfused rat livers through elevated gluconeogenesis and glycogenolysis, while reducing glycolysis, and raises plasma glucose levels in rats. Glucagon secretion decreases following food intake in healthy rats and humans, yet remains unchanged or increases in individuals with type 2 diabetes.