The activity of NADH-methemoglobin reductase varies widely among leprosy patients under dapsone treatment and is negatively correlated to their hemoglobin level. It is supposed that this correlation might be due to an increase in the reticulocyte rate in leprosy patients. In a study, no significant correlation was found between the NADH-methemoglobin reductase activity and the hemoglobin level in males and in females or between the former and the reticulocyte rate.533483484