Carbon Dioxide

Test Overview

A carbon dioxide test measures the total amount of the three forms of carbon dioxide (bicarbonate, carbonic acid, and dissolved carbon dioxide) in your blood. This test is also called a total carbon dioxide or TCO₂ test.

Carbon dioxide (CO₂) is a gaseous waste product made from metabolism. The blood carries carbon dioxide to your lungs, where it is exhaled. More than 90% of carbon dioxide in your blood exists in the form of bicarbonate (HCO₃). The remainder of the carbon dioxide is either dissolved carbon dioxide gas (CO₂) or carbonic acid (H₂CO₃).

Your kidneys and lungs balance the levels of carbon dioxide, bicarbonate, and carbonic acid in the blood.

This test is usually done at the same time as an arterial blood gas test.

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Author:	Sydney Youngerman-Cole, RN, BSN, RNC	Last Updated June 23, 2006
Medical Review:	Adam Husney, MD - Family Medicine R. Steven Tharratt, MD, MPVM, FACP, FCCP - Pulmonology, Critical Care, Medical Toxicology
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