Metformin-Induced Hemolytic Anemia in a Patient With Glucose-6-Phosphate Dehydrogenase Deficiency

Metformin, an oral antidiabetic agent, is considered the preferred first-line therapy for patients with type II diabetes. Between 2010 and 2012, it has been estimated that 14 million Americans were administered an oral antidiabetic agent, suggesting the extensive use of metformin among the diabetic population. There have been few case reports implicating metformin in causing hemolytic anemia. We present a case of a 53-year-old white male who developed hemolytic anemia after the initiation of treatment with metformin 500 mg twice daily. The patient experienced a 1.5 g/dL decrease in hemoglobin from baseline and a 2.8 mg/dL increase in total bilirubin within 1 day of treatment. Laboratory results confirmed that the patient was also glucose-6-phosphate dehydrogenase deficient. The hemolytic anemia resolved on discontinuation of metformin. Although this adverse effect seems to be rare, it is important to consider its seriousness. Clinicians should be advised to closely monitor patients newly started on metformin.