Methemoglobin forms in the blood as a result of iron oxygenation and is normally converted back to hemoglobin. Though Methemoglobin is a form of hemoglobin, it does not carry oxygen. In cases where there is too much methemoglobin in the blood, body does not get adequate oxygen. Methemoglobinemia can be the result of a genetic disorder, or it can be caused by later exposure to certain chemical agents.
A prominent sign of methemoglobinemia is that the blood becomes brownish in color, instead of the normal red color. Other symptoms may include depression, weakness, rapid breathing, discoloration of skin and mucous membranes, jaundice, vomiting, hypothermia and swelling of face or jaw.