Metformin is a synthetic biguanide compound primarily used as an oral antihyperglycemic agent. It is not an endogenous hormone but is derived from the plant Galega officinalis, which contains guanidine, a precursor to metformin. Metformin belongs to the chemical class of biguanides and is widely recognized for its role in managing type 2 diabetes mellitus. Researchers have found that metformin's primary physiological role is to lower blood glucose levels by improving insulin sensitivity, particularly in the liver and muscle tissues. It is also being explored for its potential benefits in treating other conditions such as polycystic ovary syndrome, aging, and various metabolic disorders. Metformin's mechanism of action involves the activation of AMP-activated protein kinase (AMPK), which plays a crucial role in cellular energy homeostasis. This activation leads to decreased hepatic glucose production, increased insulin sensitivity, and enhanced peripheral glucose uptake. Additionally, metformin affects the gut microbiome and increases GLP-1 levels, contributing to its glucose-lowering effects. Pharmacokinetically, metformin has an oral bioavailability of 50-60% and is not metabolized by the liver. It is excreted unchanged in the urine, with a half-life of approximately 4-8 hours. Clinically, metformin is the first-line treatment for type 2 diabetes and is approved by regulatory agencies worldwide. It is available in immediate and extended-release formulations to mitigate gastrointestinal side effects, which are common but typically manageable with dose adjustments. Researchers continue to investigate its broader therapeutic applications, including its potential role in longevity and disease prevention.