The normal range for a carbon dioxide blood test is 23 to 29 milliequivalent units per liter, explains Healthline. Normally, doctors order a blood pH level test along with a CO2 blood test. A pH test measures alkalinity or acidity of the blood and helps determine the cause of symptoms.
Doctors order CO2 or pH level tests when a patient shows symptoms of carbon dioxide and oxygen imbalance, according to Healthline. These symptoms include shortness of breath or other difficulties breathing, vomiting, and nausea. Doctors order these tests routinely when a patient is on oxygen therapy or following certain surgeries to ensure lung functionality.