Metformin toxicity in the intensive care unit: A case series and review of the literature.

Metformin toxicity is a life-threatening condition with high morbidity and mortality. Toxicity predominantly occurs in the setting of acute renal dysfunction, as the drug is solely eliminated by the kidneys. While this risk is widely known to clinicians, diagnosing metformin toxicity is challenging because commercially available serum metformin levels require days to weeks to result. Therefore, the intensivist must rely on medical history, clinical presentation, and routine laboratory findings to make the preliminary diagnosis. Treatment of metformin toxicity includes supportive fluid hydration, vasopressors, and emergent hemodialysis (HD). We report three critically ill patients who had near-fatal severe metformin-induced lactic acidosis. Their metformin levels were markedly higher than the toxicity threshold reported by the Federal Drug Agency. These patients made a prompt and complete recovery after the initiation of HD. We also review the pathophysiology, clinical presentation, diagnosis, and treatment of metformin toxicity.