Carbon Monoxide (CO)
A carbon monoxide blood test is used to detect poisoning from breathing carbon monoxide (CO), a colorless, odorless, poisonous gas. The test measures the amount of hemoglobin that has bonded with carbon monoxide. This amount is also called the carboxyhemoglobin level. See a picture of carbon monoxide poisoning.
When a person inhales carbon monoxide, it combines with the red blood cells that normally carry oxygen to the body's tissues and replaces the oxygen that is normally carried in the blood. As a result, less oxygen is carried to the brain and other body tissues. Carbon monoxide can cause severe poisoning and death.
Carbon monoxide is made during burning when there is not enough oxygen present for complete combustion. The main sources of carbon monoxide are automobile exhaust fumes, fires burning with poor ventilation (such as gas heaters and indoor cooking fires), factories, and smoking tobacco.
Why It Is Done
A carbon monoxide blood test is used to detect poisoning from breathing carbon monoxide. You might have this test if you have been exposed to the gas or if you have unexplained symptoms, such as:
How To Prepare
Do not smoke before you have this test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
How It Is Done
The health professional drawing blood will:
How It Feels
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
There is very little chance of a problem from having blood sample taken from a vein.
A carbon monoxide blood test is used to detect poisoning from breathing carbon monoxide (CO), a colorless, odorless, poisonous gas. The test measures the amount of hemoglobin that has bonded with carbon monoxide. This is also called the carboxyhemoglobin level.
Carbon monoxide results are reported as a percentage: The amount of carbon monoxide bound to hemoglobin is divided by the total amount of hemoglobin (and then multiplied by 100). The higher the percentage, the greater the risk of having symptoms of carbon monoxide poisoning. With values below 10%, a person may not have any symptoms of poisoning.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Results are usually available right away.
High blood carbon monoxide values are caused by carbon monoxide poisoning. Symptoms of carbon monoxide poisoning become more severe as the carbon monoxide levels increase.
Women and children may have more severe symptoms of carbon monoxide poisoning at lower carbon monoxide levels than men because women and children usually have fewer red blood cells.
What Affects the Test
What To Think About
eMedicineHealth Medical Reference from Healthwise
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