Background: Vitamin C is often used by complementary and alternative medicine practitioners for its antioxidant properties. We describe a case of severe hemolytic anemia and methemoglobinemia paradoxically resulting from an oxidative stress of high dose vitamin C in a patient with previously undiagnosed glucose-6-phosphate dehydrogenase (G6PD) deficiency. Case Presentation: A 47-year-old man presented with severe hemolytic anemia and methemoglobinemia days after receiving 395 g of intravenous (IV) vitamin C at an alternative medicine practice. He was managed conservatively with transfusions and his hemolysis subsided after several days. His G6PD level, measured months after his presentation, was deficient at 0.4 units/g. Conclusion: While vitamin C is often considered an antioxidant, its utilization in tissues produces its oxidized form (dehydroascorbic acid) which depletes intra-erythrocyte stores of glutathione. Patients with G6PD deficiency have reduced abilities to restore intracellular glutathione, placing them at risk for oxidative stress, and subsequent hemolysis that can be life threatening.

Keywords: Case report, hemolysis, methemoglobinemia, vitamin C, glucose-6-phosphate dehydrogenase deficiency