With an arterial blood gas pH, 7.46, pCO2, 31.1 mm Hg, pO2, 83.3 mm Hg, HCO3, 20 mEq/L, lactate, 3.6 mmol/L, and methemoglobin, 40%, the patient was considered to have methemoglobinemia. Here, HBG2 is linked to methemoglobinemia.