Metformin in 2019.

Metformin is the first-line pharmacologic treatment for type 2 diabetes and the most commonly prescribed drug for this condition worldwide, either alone or in combination with insulin or other glucose-lowering therapies. Metformin is a biguanide, a drug class of herbal origin that has been widely used to treat diabetes since the 1950s. Two other biguanides were withdrawn from clinical use because they caused lactic acidosis. Metformin was also taken off the US market due to concerns over lactic acidosis, but it subsequently has been proven safe and effective in lowering glucose levels and was reintroduced in 1995. Optimal metformin use requires clear understanding of its effects, dosing, safety, and alternatives.