Platform
Company
Blood Gases
Review status
Currently under review
Pending specialist review and validation.
This test measures the fraction of your hemoglobin that is bound to carbon monoxide in an arterial blood sample. A specialized analyzer called a co-oximeter separates and quantifies different forms of hemoglobin to determine how much is tied up by carbon monoxide.
Arterial sampling shows the oxygen-carrying status of blood as it leaves your lungs. The result helps your care team assess recent exposure to carbon monoxide and how effectively your blood can deliver oxygen to your tissues.
Carbon monoxide binds to hemoglobin with high affinity, limiting oxygen delivery to vital organs. Clinicians order this test when exposure is suspected, such as from smoke inhalation, faulty heaters, indoor engines, or certain workplace solvents, and when people present with headache, dizziness, confusion, or unexplained flu-like symptoms. It is also used to monitor response to treatment after removal from the source and oxygen therapy.
Results can guide decisions about the intensity and duration of oxygen therapy, the need for hyperbaric oxygen, and observation. The test is often paired with other blood gas and co-oximetry measures to provide a complete picture of oxygen transport and potential toxins affecting hemoglobin.
Your result is interpreted alongside your symptoms, exposure history, physical exam, and other co-oximetry values such as oxyhemoglobin and methemoglobin, as well as arterial blood gas measurements. Smokers and people exposed to indoor air pollution may have higher baseline values, so your clinician will consider your usual environment and habits when reviewing the number.
If your level is higher than expected or you have concerning symptoms, your team may advise immediate removal from exposure, high-flow oxygen, and repeat testing to track the decline over time. Pregnant individuals and newborns can be more vulnerable to the effects of carbon monoxide, so clinicians may act sooner in these situations. Always discuss next steps with your care team, especially if symptoms persist or exposure may continue.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Active smoking and exposure to secondhand smoke increase carboxyhemoglobin because smoke contains carbon monoxide. Your baseline may be higher if you smoke regularly.
Faulty heaters, indoor generators, car exhaust in enclosed spaces, and certain solvents that metabolize to carbon monoxide can raise levels quickly. Tell your clinician about recent home or job exposures.
Breathing supplemental oxygen before the blood draw can lower carboxyhemoglobin by speeding the elimination of carbon monoxide, which may reduce the measured value.
Using the wrong specimen type, mixing venous with arterial blood, delays to analysis, or air contamination can affect co-oximetry measurements. Proper arterial collection and prompt testing help ensure accuracy.
Lung or heart disease that limits oxygenation can worsen symptoms at a given level. Increased red blood cell breakdown can also produce more endogenous carbon monoxide and mildly raise the value.
Pregnant individuals and newborns may be more sensitive to the effects of carbon monoxide on oxygen delivery. Clinicians may use a lower threshold for concern and intervene sooner.
References