However, if consumed at a dose of more than 200 mg/day, it can cause methemoglobinemia, a condition characterized by elevated methemoglobin levels in the blood; methemoglobin is an abnormal form of hemoglobin, containing iron in the ferric state (Fe<sup>3</sup> <sup>+</sup>) rather than the reduced ferrous form (Fe<sup>2</sup> <sup>+</sup>) found in hemoglobin. This evidence concerns the gene HBG2 and methemoglobinemia.