Serum or plasma concentration of carbon monoxide (CO)

What Is This Test Measuring?

Carbon monoxide binds to hemoglobin in red blood cells, forming carboxyhemoglobin (COHb). This test quantifies the percentage of hemoglobin saturated with CO, which can indicate exposure to sources like smoke, fumes, or industrial environments. Normal levels are typically low, as the body naturally metabolizes CO over time.

Why Might You Need This Test?

Your healthcare provider may order this test if you’ve experienced symptoms like headache, dizziness, nausea, or shortness of breath after exposure to carbon monoxide, or if you live in an area with known pollution or smoke hazards.

How Is the Test Performed?

A small blood sample is drawn from a vein, usually in your arm. The sample is processed to separate serum or plasma, where CO levels are measured using a specialized analytical method (often immunoassay or chemiluminescence). Results are reported as a percentage of COHb in your blood.

What Do Results Mean?

Results are not typically provided as a single reference range for COHb, as levels vary based on exposure duration and individual factors. High levels may suggest recent exposure requiring medical evaluation, while low levels do not necessarily rule out past exposure.