Metformin is a synthetic biguanide compound primarily used as an oral antihyperglycemic agent. It is not an endogenous hormone but is chemically synthesized and widely used in the management of type 2 diabetes mellitus. Metformin is classified under the biguanide class of compounds and is available under various brand names, including Glucophage, Fortamet, and Riomet. It is not produced naturally in the body and is administered orally. Researchers have extensively studied metformin for its role in glucose metabolism and its potential benefits in other metabolic disorders. The primary physiological role of metformin is to lower blood glucose levels, primarily by reducing hepatic glucose production and improving insulin sensitivity. Research areas include its effects on weight management, cardiovascular health, and potential anti-aging properties. Metformin's mechanism of action involves the activation of the AMP-activated protein kinase (AMPK) pathway, which plays a crucial role in cellular energy homeostasis. By activating AMPK, metformin decreases hepatic glucose production and increases insulin sensitivity in peripheral tissues. Additionally, it may influence the gut microbiota and improve glucose uptake in muscle cells. Metformin has a half-life of approximately 4 to 8.7 hours and is primarily excreted unchanged in the urine. It has a bioavailability of 50-60% when taken orally, with absorption occurring mainly in the small intestine. The drug is not metabolized by the liver, which reduces the risk of hepatic side effects. Clinically, metformin is widely used as a first-line treatment for type 2 diabetes and is approved by regulatory agencies worldwide. It is also being investigated for its potential use in polycystic ovary syndrome (PCOS) and other metabolic conditions. Metformin is generally well-tolerated, with gastrointestinal disturbances being the most common side effects. It is available by prescription and is not classified as a controlled substance.