Antidiabetic drugs (with the exception of insulin) are all pharmacological agents that have been approved for hyperglycemic treatment in type 2 diabetes mellitus (DM). If lifestyle modifications (weight loss, dietary modification, and exercise) do not sufficiently reduce A1C levels (target level: ∼ 7%), pharmacological treatment with antidiabetic drugs should be initiated. These drugs may be classified according to their mechanism of action as insulinotropic or non-insulinotropic. They are available as monotherapy or combination therapies, with the latter involving two (or, less commonly, three) antidiabetic drugs and/or insulin.

The exact treatment algorithms are reviewed in the treatment section of diabetes mellitus. The drug of choice for all type 2 diabetic patients is metformin. This drug has beneficial effects on glucose metabolism and promotes weight loss or at least weight stabilization. In addition, numerous studies have demonstrated that metformin can reduce mortality and the risk of complications. If metformin is contraindicated, not tolerated, or does not sufficiently control blood glucose levels, another class of antidiabetic drug may be administered.

Most antidiabetic drugs are not recommended or should be used with caution in patients with moderate or severe renal failure or other significant comorbidities. Oral antidiabetic drugs are not recommended during pregnancy or breastfeeding.