HBG2 and hyperinsulinemic hypoglycemia, familial, 4: Calabrese et al. explained that ascorbic acid significantly reduced the in vitro occurrence of sodium nitrite-induced methemoglobin (METHB) formation at a dose-dependent manner in erythrocytes from G6PD-deficient humans.27 Rajabi and Ale Davood suggested that treatment with ascorbic acid was possible in methemoglobinemic condition caused by toxic effects or by congenital methemoglobin reductase deficiency.28 However, methylene blue therapy is necessary when methemoglobin content of the blood is critically increased more than 30%.