Carbon Monoxide (CO)

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Test Overview

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.

Last updated:	March 18, 2008
Author:	Maria G. Essig, MS, ELS
Reviewed By:	Caroline S. Rhoads, MD - Internal Medicine, R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care, Medical Toxicology
Editors:	Susan Van Houten, RN, BSN, MBA, Tracy Landauer