Table 2.

Clinical symptoms in relation to MetHb blood concentration.

MetHb % of total Hb	Symptoms
<10	Asymptomatic
10-20	Cyanosis
20-40	Headache, fatigue, weakness, tachycardia, and dizziness
40-50	Dyspnea and lethargy
50-70	Acidosis, arrhythmias, hypoxia, seizures and coma
>70	Death

MetHb, methemoglobin; Hb, hemoglobin.