Metformin-Associated Lactic Acidosis in a Patient With Normal Renal Function

We report a case of metformin-associated lactic acidosis (MALA) in the setting of normal renal function and review the relevant medical literature. A 77-year-old female diagnosed with type 2 diabetes mellitus previously treated with insulin and gliclazide MR was started on metformin. A few weeks later, she was found to have lactic acidosis. Renal function was normal, and no severe underlying illness was identified. Metformin was discontinued, and lactate levels normalized within 4 days, suggesting metformin was a reversible precipitant of the lactic acidosis. MALA can occur in the absence of renal impairment, systemic hypoperfusion or severe liver disease. A possible mechanism is a genetically determined alteration in metformin pharmacokinetics. Metformin is beneficial and safe in patients with normal renal function, but the development of MALA, although rare, should be kept in mind to prevent potentially life-threatening toxicity.