Fatal metformin-associated lactic acidosis in a healthy woman after massive overdose

Metformin is widely prescribed for type 2 diabetes mellitus and is generally considered safe. However, metformin-associated lactic acidosis (MALA) is a rare but potentially fatal complication. Although typically associated with renal or hepatic dysfunction, intentional overdose can also lead to severe acidosis and high mortality. A 42-year-old woman with no medical history ingested 12 g of metformin in a suicide attempt. She presented with stable vital signs and normal renal and hepatic function. Initial arterial blood gas showed metabolic acidosis (pH 7.21, HCO₃ ^- 12 mmol/L, lactate 8 mmol/L). Intermittent hemodialysis was initiated, but her acidosis worsened. She developed hypotension requiring norepinephrine and subsequently deteriorated neurologically. Despite 2 hemodialysis sessions, she progressed to cardiac arrest and died. This case demonstrates that massive metformin overdose can overwhelm normal metabolic and clearance mechanisms, resulting in refractory lactic acidosis. Even with early hemodialysis, tissue sequestration of metformin and ongoing mitochondrial dysfunction may sustain lactate overproduction. Massive metformin overdose can be fatal even in healthy individuals. Close monitoring is essential, and prolonged or continuous renal replacement therapies may be warranted when initial dialysis fails to correct severe acidosis.