HBG2 and type 2 diabetes mellitus: A methemoglobin level up to 15% of total hemoglobin is asymptomatic in healthy patients; headache and fatigue is associated with a level ranging from 15% to 30%; dizziness, dyspnea, and syncope occur at levels of 30–50%; and at levels higher than 50%, central nervous system (CNS) depression, coma, and death are expected [2, 7].