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Carbon Monoxide (CO)

Results continued...

Results are usually available right away.

Normal

Carbon monoxide 1
Nonsmokers:

Less than 2% of total hemoglobin

Smokers:

4%–8% of total hemoglobin

High values

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.

Symptoms related to high carbon monoxide values 1
Percent of total hemoglobin Symptoms

20%–30%

Headache, nausea, vomiting, and trouble making decisions

30%–40%

Dizziness, muscle weakness, vision problems, confusion, and increased heart rate and breathing rate

50%–60%

Loss of consciousness

Over 60%

Seizures, coma, death

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

  • Smokers already have some carbon monoxide in their blood.
  • People who are regularly exposed to car exhaust, such as taxi drivers and traffic police, often have high carbon monoxide levels (8% to 12%).

What To Think About

  • A person with symptoms and possible exposure to carbon monoxide, such as someone who lives in a house with an old heating system and complains of ongoing headaches, should be tested for carbon monoxide poisoning.
  • A person who may have carbon monoxide poisoning should be removed from the place of likely exposure and given oxygen to breathe before being tested.
  • If carbon monoxide poisoning is suspected, other tests (such as arterial blood gases and a complete blood count) may be done. An arterial blood gas (ABG) test may be done to determine whether symptoms are caused by carbon monoxide poisoning or by another disease that causes similar symptoms.

Citations

  1. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.

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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