The oral biguanide metformin (Glucophage, and others) is generally the drug of choice for initial treatment of type 2 diabetes. It has also been used to prevent or at least delay the onset of diabetes in patients considered to be at high risk for the disease. Recent guidelines recommend considering use of metformin in patients with prediabetes (fasting plasma glucose 100-125 mg/dL, 2-hr post-load glucose 140-199 mg/dL, or A1C 5.7-6.4%), especially in those who are <60 years old, have a BMI >35 kg/m2, or have a history of gestational diabetes.1 Metformin has not been approved for such use by the FDA.
Metformin for Prediabetes. JAMA. 2017;317(11):1171. doi:10.1001/jama.2016.17844