Metformin is the first-line pharmacological therapy for type 2 diabetes. It is the only glucose-lowering oral drug that has been shown to reduce mortality in patients with diabetes. The most common adverse effect is gastrointestinal upset. Starting at a low dose and increasing it slowly reduces this risk. Taking metformin with food also helps. Numerous contraindications to the use of metformin are listed in the product information, including reduced renal function. Strict adherence to these recommendations may deny a valuable drug to many patients.