Gastrointestinal adverse effects including anorexia, nausea and diarrhea may occur and is dose dependent. These effects can be limited by administering with food and starting with a low dose (500 mg once or twice daily), then slowly titrating the dose upwards according to the clinical response. Patients may experience a metallic taste and there may be weight loss. Absorption of various substances including Vitamin B12 may be impaired. Hypoglycemia is less than of a problem with Metformin than with the sulfonylureas.
Lactic acidosis is rare and occurs predominantly in patients with renal impairment.