Carbon dioxide levels are almost always done as part of an electrolyte panel to tell your doctor whether your sodium, potassium, chloride, and bicarbonate (H2CO3-, measured as total CO2) are in balance. They may be done as part of an annual screen, included as part of a basic or comprehensive metabolic panel, or done when your doctor suspects an imbalance. The CO2 test is also done when your doctor is evaluating your acid-base balance, to screen for an imbalance, and to monitor a known problem during treatment.

Carbon dioxide testing may be ordered, usually as part of an electrolyte panel when:

• you are having a routine annual blood screen;
• your doctor suspects that you may be retaining water or are dehydrated, upsetting your electrolyte balance;
• to evaluate your body’s acid-base balance (pH);
• to monitor a condition or treatment that might cause an electrolyte imbalance.

When CO2 levels are higher than normal, it suggests that your body is having trouble maintaining its pH balance by releasing excess carbon dioxide or that you have upset your electrolyte balance, perhaps by losing or retaining fluid. Both of these imbalances may be due to a wide range of dysfunctions. CO2 elevations may be seen with chronic lung-related problems, such as emphysema, and metabolic problems, such as severe diarrhea or prolonged vomiting (which can cause metabolic alkalosis – an excessive loss of body acidity).

Low CO2 levels may be seen with respiratory alkalosis (which can be caused by hyperventilation), metabolic acidosis, shock, starvation, and during kidney failure.

PLEASE NOTE: Numerically reported test results are interpreted according to the test's reference range, which may vary by the patient's age, sex, as well as the instrumentation or kit used to perform the test. A specific result within the reference (normal) range – for any test – does not ensure health just as a result outside the reference range may not indicate disease. To learn more about reference ranges, please see the article, Reference Ranges and What They Mean. To learn the reference range for your test, consult your doctor or laboratorian. Lab Tests Online recommends you consult your physician to discuss your test results as a part of a complete medical examination.

Some drugs may increase blood carbon dioxide levels including: aldosterone, barbiturates, bicarbonates, hydrocortisone, loop diuretics, and steroids.

Drugs that may decrease blood carbon dioxide levels include methicillin, nitrofurantoin, tetracycline, thiazide diuretics, and triamterene.