Metformin-Associated Lactic Acidosis in Individuals Without Chronic Kidney Disease on Therapeutic Dose: A Case Report.

Metformin-associated lactic acidosis (MALA) is a severe side effect of metformin treatment. We encountered an exceedingly rare case of MALA in a patient taking metformin at recommended doses who had no risk factors except for advanced age. A 77-year-old male with a diagnosis of lactic acidosis was referred to our facility. He was taking 250 mg/day of metformin for diabetes. Although he had no pre-existing chronic kidney disease, he developed acute kidney injury upon admission, leading to the diagnosis of MALA based on the test results and history of metformin use. His lactic acidosis improved without extracorporeal treatment through metformin discontinuation and proper circulatory management. When encountering patients with unexplained lactic acidosis, it is important to consider MALA as part of the differential diagnosis and to confirm the patient's medication history. Specifically, when metformin use is identified, attention should be directed toward the potential for MALA.