Carboxyhaemoglobin - blood

Last updated: Thursday, 08, April, 2004

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Item Process
Specimen1 mL blood in EDTA.


Reference Interval

Carboxyhaemoglobin 0.2-2.0% of total haemoglobin in normal blood; up to 8.5% in heavy smokers.


Investigation of possible carbon monoxide exposure and poisoning.


In carbon monoxide poisoning, carboxyhaemoglobin levels provide an approximate guide to status.
Between 10-20%: headache and dyspnoea on exertion;
above 20%: confusion and irritability;
above 50%: unconsciousness, with death likely if exposure is prolonged;
above 70%: death is rapid.

Toxicity relates more to inhibition of mitochondrial cytochrome respiration than to interference with blood oxygen transport.

ReferenceGorman D et al. Toxicology. 2003; 187(1): 25-38.