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Carbon Monoxide (CO)

A carbon monoxide blood test is used to detect carbon monoxide poisoning. Poisoning can happen if you breathe air that contains too much carbon monoxide (CO). This gas has no color, odor, or taste, so you can't tell when you are breathing it. The test measures the amount of hemoglobin in your blood that has bonded with carbon monoxide.

Carbon monoxide can come from any source that burns fuel. Common sources are cars, fireplaces, powerboats, woodstoves, kerosene space heaters, charcoal grills, and gas appliances such as water heaters and ovens. These things usually cause no problems. But if they are not used or installed properly, carbon monoxide may build up in an enclosed space.

When you inhale carbon monoxide camera.gif, it replaces the oxygen that is normally carried by the hemoglobin in your red blood cells. As a result, your brain and other tissues get less oxygen. This can cause serious symptoms or death.

Why It Is Done

This test may be done if you have been exposed to carbon monoxide or if you have unexplained symptoms, such as:

How To Prepare

Do not smoke before you have this test. Tobacco smoke contains carbon monoxide.

Talk to your doctor if you have any concerns about 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 taking a sample of your 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: August 07, 2014
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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