Definition of methemoglobin in English:


(British methaemoglobin)

Pronunciation /metˈhēməˌɡlōbən//ˌmetˌhēməˈɡlōbən/


  • A stable oxidized form of hemoglobin which is unable to release oxygen to the tissues, produced in some inherited abnormalities and by oxidizing drugs.

    • ‘In the normal physiological state, small amounts of methemoglobin are formed during the reaction between oxygen and hemoglobin, but these amounts are typically limited to less than 0.02 of the total amount of hemoglobin.’
    • ‘Patients with red cell breakdown, for example in malaria, pass haemoglobin into the urine, where it is broken down to the brown pigment methaemoglobin; hence one form of malaria is called ‘black-water fever’.’
    • ‘Red cells are lysed and potassium ferricyanide oxidizes hemoglobin to methemoglobin, which combines with potassium cyanide forming cyanmethemoglobin.’
    • ‘In addition, the enzyme systems for reducing methemoglobin to oxyhemoglobin are incompletely developed in infants under six months of age.’
    • ‘Methemoglobinemia is detectable by measurement of blood levels of methemoglobin and is manifested clinically as cyanosis and hypoxia.’