Taking metformin may cause dizziness. Metformin is a biguanide hypoglycemic agent for type 2 diabetes mellitus, especially obese type 2 diabetes mellitus, that has failed treatment with dietary control and physical activity alone. Possible adverse reactions to this product include diarrhea, nausea, vomiting, bloating, malaise, dyspepsia, headache, myalgia, dizziness, lightheadedness, rash, and weight loss. Metformin also reduces vitamin B12 absorption and lactic acidosis is rare. Contraindications to this product include severe infections and trauma, major surgical procedures, clinical hypotension and hypoxia; acute or chronic metabolic acidosis; congestive heart failure, and other serious cardiac and pulmonary disorders; renal failure; hypersensitivity to metformin; alcoholics; and uncorrected vitamin B12 and folate deficiencies. Metformin should be taken under medical supervision, do not take it on your own, and you should consult your doctor if you experience dizziness.