A normal value for a carbon dioxide blood test is between 23 and 29 mEq/L, according to the U.S. National Library of Medicine. The severity of an abnormal test result is dependent on the underlying condition in the patient.
The level carbon dioxide in the liquid part of the blood -serum- is controlled by the lungs and kidneys. If the lungs and kidneys are unable to remove large amounts of carbon dioxide from the body, respiratory failure and damage to vital organs may result.
Conditions that cause abnormal levels include diarrhea, vomiting, ethylene glycol or methanol poisoning, breathing disorders and Cushing syndrome, cites the U.S National Library of Medicine.