Carboxyhaemoglobin
What this test measures
Carboxyhaemoglobin is haemoglobin bound to carbon monoxide instead of oxygen. It shows recent exposure to carbon monoxide from smoke, fumes or faulty appliances.
Why doctors request it
Measured on a blood gas or by a breath monitor in smoking clinics, after fires, and when carbon monoxide poisoning is suspected.
What commonly pushes it up
- Smoking, which typically gives 3 to 10 percent
- Exposure to exhaust fumes, fires or faulty gas appliances
- Living in heavy traffic
What commonly pushes it down
- There is no meaningful low value
Everyday reasons for a value outside the range
- Smokers routinely run above the non-smoker range
About the sample
Analysed promptly; the level halves every four to five hours in fresh air.
Upload a photo or PDF and see every line against the range your lab printed, explained in plain English. First report free.
Read my report freeThis is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.