A 13-year-old female patient presented to the hospital after ingesting 150 grams of metformin, a significant overdose. As a result, she developed severe metabolic acidosis, hyperlactatemia, and acute kidney injury, which are known complications of acute metformin toxicity. The patient's condition was critical, requiring intubation and continuous renal replacement therapy to manage her metabolic disturbances. Metabolic acidosis and hyperlactatemia are well-documented consequences of metformin overdose, and the patient's initial presentation was consistent with these expected complications. Despite prompt treatment and rapid correction of her metabolic acidosis, the patient developed a unexpected complication - biventricular cardiac dysfunction. This cardiac dysfunction required the use of vasopressors and milrinone, medications that support heart function. Fortunately, the patient's cardiac function improved over time, and by hospital day 8, she was able to be extubated and discontinued from all vasopressors and inotropes. A follow-up echocardiogram performed one week later showed normalization of her biventricular function, indicating complete recovery from the cardiac dysfunction. This case highlights the importance of recognizing acute, reversible cardiotoxicity as a potential complication of large, acute metformin ingestions, in addition to the more commonly acknowledged metabolic complications. The fact that the patient developed cardiac dysfunction despite rapid correction of her metabolic acidosis suggests that the cardiotoxic effects of metformin may be independent of its metabolic effects, and clinicians should be aware of this potential complication when managing patients with metformin overdose. Link: https://pubmed.ncbi.nlm.nih.gov/40368398/