Symptomatology according to methemoglobin level [8, 1, 2, 9]
15–30%	∙ Cyanosis, asthenia, dizziness, headache
30–50%	∙ Dyspnea, tachypnea, syncope
50–70%	∙ Obnubilation, coma, convulsions, circulatory failure, rhythm disorders
Over 70%	∙ Risk of death