Gastrointestinal disorders such as nausea, vomiting, diarrhea, abdominal pain and loss of appetite may occur. Patients may experience a metallic taste and there may be weight loss. Skin reaction such as erythema, pruritus and urticaria. Lactic acidosis, sometimes fatal, has occurred with metformin hydrochloride. Absorption of various substances including vitamin B
12 may be impaired.