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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.

When a person inhales carbon monoxide camera.gif, 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 engine fumes (such as from cars or boats), 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:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Attach a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure on the site and then put on a bandage.
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WebMD Medical Reference from Healthwise

Last Updated: March 01, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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