Our global life sciences company brings diagnostic testing & drug development together.

Carbon Dioxide, Total

CPT: 82374
Updated on 08/15/2021
Print Share


  • CO2
  • TCO2

Special Instructions

Maintain specimen in a tightly-stoppered tube.

Expected Turnaround Time

Within 1 day

Related Documents

Specimen Requirements


Serum (preferred) or plasma


1 mL

Minimum Volume

0.7 mL (Note: This volume does not allow for repeat testing.)


Red-top tube, gel-barrier tube, or green-top (lithium heparin) tube. Do not use oxalate, EDTA, or citrate plasma.

Gel-barrier tube (send entire tube) is preferred; red-top tube or green-top (lithium heparin) tube is acceptable if centrifuged within 45 minutes and the serum or plasma is removed and placed in a tightly-stoppered secondary tube.

Red-top tube, gel-barrier tube, or green-top (lithium heparin) tube. Do not use oxalate, EDTA, or citrate plasma.


Separate serum or plasma from cells within 45 minutes of collection.

Draw blood in gel-barrier tube and centrifuge. If red-top tube or green-top tube is used, centrifuge within 45 minutes of draw, remove the serum or plasma, and place in a transport tube and tightly stopper the tube.

Separate serum or plasma from cells within 45 minutes of collection.

Storage Instructions

Room temperature

Stability Requirements



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Improper collection and storage; improper labeling

Test Details


Evaluate the total carbonate buffering system in the body, acid-base balance. High results may represent respiratory acidosis with CO2 retention, or metabolic alkalosis (eg, prolonged vomiting). Low value may indicate respiratory alkalosis as in hyperventilation or metabolic acidosis (eg, diabetes with ketoacidosis).


Interpretation requires clinical information and the other electrolytes.



Reference Interval

See table.


Range (mmol/L)

0 to 30 d


31 d to 1 y


2 to 5 y


6 to 12 y


>12 y


Additional Information

“Total carbon dioxide” consists of CO2 in solution or bound to proteins, HCO3, CO32−, and H2CO3. In practice, 80% to 90% is present as bicarbonate (HCO3). “Hypercapnia” means excessive carbon dioxide in the blood. Impaired elimination of CO2 reflects interaction of abnormalities in respiratory drive, the muscles of respiration, and the function of the lung. Elimination of carbon dioxide from the lung involves alveolar ventilation but not dead-space ventilation. Partitioning of these spaces is expressed as a ratio between dead space and total volume per breath: the tidal volume. The tidal volume normally is <0.30. These and other aspects of pulmonary gas exchange, ventilation and their consequences are addressed as the partial pressure of arterial carbon dioxide, PaCO2, a part of arterial blood gases.1


1. Weinberger SE, Schwartzstein RM, Weiss JW. Hypercapnia. N Engl J Med. 1989 Nov 2; 321(18):1223-1231. 2677729


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
001578 Carbon Dioxide, Total 2028-9 001578 Carbon Dioxide, Total mmol/L 2028-9

For Providers

Please login to order a test

Order a Test

© 2021 Laboratory Corporation of America® Holdings and Lexi-Comp Inc. All Rights Reserved.

CPT Statement/Profile Statement

The LOINC® codes are copyright © 1994-2021, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at Additional information regarding LOINC® codes can be found at, including the LOINC Manual, which can be downloaded at