Aim and background: Metformin and clonazepam mixed-drug poisoning is rare and life-threatening. Early diagnosis, aggressive treatment, and careful monitoring are essential for improving patient outcomes. Case description: A 36-year-old man with bipolar disorder attempted suicide by ingesting 45 gm of metformin and 30 gm of clonazepam. He developed central nervous system depression, severe lactic acidosis, acute kidney injury (AKI), and liver injury. The patient suffered cardiac arrest with ventricular fibrillation and required defibrillation and mechanical ventilation. The primary goals of therapy were prompt removal of metformin and clonazepam, restoration of acid-base balance, and management of AKI. Treatment included consistent sodium bicarbonate infusion, prompt initiation of hemodialysis, an aggressive antibiotic regimen, mechanical ventilation, flumazenil treatment to manage clonazepam toxicity, and long-term supportive care. Despite a poor prognosis, the patient survived and was discharged after a hospital stay of 50 days. The patient has recovered completely and is routinely following up with his consulting physician. Conclusion: Despite severe acidosis, metformin-induced lactic acidosis warrants immediate treatment with renal replacement therapy and sodium bicarbonate. Clinical significance: Emergency physicians and intensivists should be aware of the need for a multifaceted intervention approach involving sustained low-efficiency dialysis, extracorporeal therapy, hemodynamic support, and meticulous acid-base balance management, which are crucial for the survival of patients presenting with severe lactic acidosis.