Acute overdose of metformin can show potentially fatal lactic acidosis. Management should be directed towards close monitoring of renal function and hemodynamics. Patients may require dialysis or extracorporeal membrane oxygenation in cases of hemodynamic instability. This case presents an adolescent with massive metformin ingestion estimated at 100 g leading to metformin-associated lactic acidosis and subsequent respiratory failure, cardiovascular collapse, and acute kidney injury. The complications were successfully managed with venoarterial extracorporeal membrane oxygenation, continuous renal replacement therapy, and mechanical ventilation.