Table 2.

Symptoms and Signs in a Patient with Methemoglobinemia (Adopted from Ludlow et al).²

% MetHb	Symptoms
<15	Generally Asymptomatic
15–30	Cyanosis, anxiety, light-headedness, fatigue, headache
30–50	Tachypnea, confusion, syncope
50–70	Seizures, arrhythmias, metabolic acidosis, coma
>70	Death