Methemoglobin

It works by converting hemoglobin to methemoglobin, which allows for the binding of cyanide (CN–) anions by ferric (Fe3+) cations and the formation of cyanomethemoglobin.

Percentage of methemoglobin is likely a better indicator of illness severity than overall concentration, as underlying medical conditions play an important role.

[9] This may be further compounded by the "functional hemoglobin's" decreased ability to release oxygen in the presence of methemoglobin.

Anemia, congestive heart failure, chronic obstructive pulmonary disease, and essentially any pathology that impairs the ability to deliver oxygen may worsen the symptoms of methemoglobinemia.

Upon exiting the body, bloodstains transit from bright red to dark brown, which is attributed to oxidation of oxy-hemoglobin (HbO2) to methemoglobin (met-Hb) and hemichrome (HC).