A 39-year-old man presented to the emergency department after intentionally ingesting 50 tablets of metformin 1,000 mg. The reported time of ingestion was 6 h prior to arrival. Vital signs were: temperature, 37.4°C; pulse, 94 beats per minute; blood pressure, 117/74 mmHg; respirations, 16/min; and oxygen saturation, 96 % on room air. Gastric lavage was performed, and a single dose of activated charcoal was given. His initial serum lactate was 4.3 mmol/L (normal00.67-1.8 mmol/L). The patient had a negative urine drug screen, and acetaminophen and salicylate levels were below detection limits. The patient was admitted for monitoring of lactic acidosis.Twenty hours after arrival, the patient became hypotensive with a blood pressure of 85/45 mmHg. Arterial blood gas analysis revealed a pH of 7.20, pCO 2 19 mmHg, and bicarbonate HCO 3 of 6 mmol/L. A repeat serum lactate at this time was 20 mmol/L, and a basic metabolic panel showed sodium of 134 mmol/L, potassium 3.8 mmol/L, chloride 98 mmol/L, bicarbonate 16 mmol/L, BUN 32 mg/ dL, and creatinine 1.3 mg/dL; the calculated anion gap was 20 mmol/L. A 1-L normal saline bolus was administered, and serum alkalinization was initiated with a sodium bicarbonate drip.