Metformin-Associated Lactic Acidosis Induced by Even Modest Amounts of Alcohol: A Case Report

A 66-year-old man with type 2 diabetes mellitus, treated with metformin, experienced loss of consciousness after bathing and consuming approximately 700 mL of beer (estimated 28 g of alcohol). He had no history of habitual heavy drinking. Upon arrival at the emergency department, he was alert (Glasgow Coma Scale score E4V5M6) with a heart rate of 73 bpm (sinus rhythm), blood pressure of 68/43 mmHg, respiratory rate of 18 breaths per minute, and oxygen saturation of 98% on room air. Arterial blood gas analysis revealed a pH of 7.33, a bicarbonate level of 16.2 mmol/L, and a lactate level of 7.4 mmol/L, consistent with lactic acidosis. These findings indicate a significant metabolic disturbance despite only modest alcohol intake. Metformin-associated lactic acidosis (MALA) was suspected, and he was admitted to the intensive care unit. Despite fluid resuscitation, hypotension required a norepinephrine infusion, which was discontinued after 12 hours. The acidemia improved, and all medications except metformin were resumed. He was discharged on hospital day 3 with stable renal function. This case underscores that even modest alcohol consumption can precipitate MALA in the presence of mild renal impairment.