Bicarbonate test; HCO3-; Carbon dioxide test; TCO2; Total CO2; CO2 test - serum
How the test is performed
A blood sample is needed. For information on how this is done, see: Venipuncture
How to prepare for the test
Your health care provider may tell you to stop taking any drugs that may affect test results. Corticosteroids and excessive use of antacids can increase bicarbonate levels.
How the test will feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
The CO2 test is most often done as part of an electrolyte or basic metabolic panel. Changes in your CO2 level may suggest that you are losing or retaining fluid, which causes an imbalance in your body's electrolytes.
CO2 levels in the blood are influenced by kidney and lung function. The kidneys are mainly responsible for maintaining the normal bicarbonate levels.
The normal range is 23-29 mEq/L (milliequivalent per liter).
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
DuBose TD Jr. Disorders of acid-base balance. In: Brenner BM, eds. Brenner and Rector’s The Kidney. 8th ed. Philadelphia, Pa: Saunders Elsevier; 2008:chap 14.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.