Carbon Dioxide(CO2) Determination Reagent is an in vitro diagnostic quantitative test kit. A CO2 blood test measures your level of bicarbonate, an indicator of how much CO2 is in your blood. CO2 is a form of natural waste that your body produces. Your blood carries CO2 to your lungs, where you breathe it out. Too little or too much CO2 in your blood may be a sign of a more serious health problem.