Metformin-associated Lactic Acidosis: An Unexpected Scenario

According to the National Diabetes Statistics Report (2017) by Centers for Disease Control and Prevention (CDC), 9.4% of the US population, approximately 30.3 million people had diabetes while 84.1 million had pre-diabetes as of 2015. In addition to lifestyle changes, the American Diabetes Association recommends metformin as the first-line treatment for type 2 diabetes. Hence, not surprisingly, metformin is a commonly prescribed medication by most healthcare providers in all clinical settings. As a result, it remains essential that all medical professionals be aware of any adverse effects as a result of metformin therapy, no matter how uncommon. We present the case of a 42-year-old lady with type 2 diabetes mellitus who required initial admission to intensive care unit (ICU) after presenting with unilateral back and lower abdominal pain with dysuria and was noted to have an acute kidney injury with a creatinine of 7.45 mg/dL and severe metabolic acidosis with a pH of 6.7 and an anion gap more than 50 mmol/L. Lactic acid was elevated at 24.2 mmol/L. Serum metformin levels were high at 14 mcg/mL (therapeutic range: 1-2 mcg/mL). She required emergent dialysis but subsequently, renal functions recovered. Risk of metformin-associated lactic acidosis (MALA) is reported to be an estimated 6.3 per 100,000 patient-years. Commonly encountered clinical scenarios such as hypoxemia, sepsis, alcohol abuse, renal injury, and shock can precipitate MALA. Early recognition allows timely initiation of appropriate therapy and reduces associated morbidity.