High dose vitamin C induced methemoglobinemia and hemolytic anemia in glucose-6-phosphate dehydrogenase deficiency.

Investigational use of intravenous vitamin C has been on the rise, but its side effects may be underreported. A 75-year-old woman presented with acute onset of jaundice, dark urine and shortness of breath after receiving 30 g of vitamin C infusion as an unconventional therapy for her hemifacial spasm. Diagnosis of methemoglobinemia and hemolytic anemia was made clinically and confirmed on laboratory tests. She recovered with supportive treatment and packed cell transfusion. Her previously unrecognised underlying condition of glucose-6-phosphate dehydrogenase (G6PD) deficiency was confirmed months after the initial presentation. This is the first reported case of methemoglobinemia and hemolytic anemia induced by high dose vitamin C in a female patient with G6PD deficiency. The dosage of vitamin C administered was also relatively low compared with previous adult reports. When administered at physiological dose, vitamin C can be used as an alternative to methylene blue in treatment of methemoglobinemia in patients with G6PD deficiency. However at supraphysiological dose vitamin C can paradoxically lead to hemolytic anemia in the same group of patients. Physicians should be alert of these potential complications of high dose vitamin C.