Test library
Carboxyhemoglobin Level Test
A carbon monoxide blood test measures carboxyhemoglobin, the form of hemoglobin bound to carbon monoxide, to assess exposure. It is used when carbon monoxide poisoning is suspected from smoke, faulty heating equipment, or vehicle exhaust.
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Order Carbon Monoxide, Blood Test- Typical turnaround
- 1-3 business days
- Starting price
- From $179
- Results
- Confidential, online
Quick answer
The carbon monoxide blood test measures carboxyhemoglobin in the blood. Carbon monoxide binds to hemoglobin far more readily than oxygen does, so elevated levels can reduce the amount of oxygen reaching tissues. The test is used when exposure is suspected, such as after smoke inhalation, a faulty furnace, or a vehicle exhaust incident. A qualified healthcare provider interprets the result with the person's symptoms.
What this test measures
Carbon monoxide is an odorless, colorless gas produced by incomplete combustion. Common sources include gas furnaces, water heaters, wood stoves, portable generators, and vehicle exhaust. Because it binds to hemoglobin with high affinity, it forms carboxyhemoglobin and displaces oxygen, which can strain the heart, brain, and other organs. Measuring carboxyhemoglobin gives an objective picture of how much exposure has occurred.
The sample is a blood draw, usually from a vein, and in urgent situations it may be obtained from an artery or analyzed with a co-oximeter. The report gives the percentage of hemoglobin bound to carbon monoxide. People who smoke often have higher baseline levels than non-smokers. Timing matters because carbon monoxide clears from the blood over hours once exposure stops, so a sample collected later may read lower than the peak.
This test is ordered when someone has symptoms that could suggest carbon monoxide poisoning, such as headache, dizziness, nausea, confusion, or shortness of breath, especially when several people or pets in the same building feel unwell. It may also confirm exposure after a known incident or check people who work around combustion equipment. Results guide next steps alongside the clinical assessment.
- Carboxyhemoglobin (COHb) percentage
- Total hemoglobin
- Oxygen saturation
- Arterial or venous blood gas panel
- Methemoglobin percentage when co-oximetry is used
- Lactate
- Blood pH and bicarbonate when a gas panel is included
Why people order this test
- Suspected carbon monoxide poisoning from a faulty appliance
- Symptoms after smoke inhalation
- Exposure to vehicle exhaust in an enclosed space
- Unexplained headache, dizziness, or nausea affecting several people in one building
- Confirmation after a workplace or home exposure incident
- Monitoring during treatment after a known exposure
How to prepare
No fasting is required. A blood sample is collected at a laboratory or, in urgent situations, in a medical setting. Because carbon monoxide clears from the blood within hours after exposure ends, the sample is usually collected as soon as possible after a suspected exposure.
Understanding your results
Results are usually available within one to three business days for routine collection. The report gives the percentage of hemoglobin bound to carbon monoxide. A higher level indicates greater exposure, and a qualified healthcare provider interprets the value with symptoms, smoking status, and timing of collection.
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Frequently Asked Questions
What does a carbon monoxide blood test measure?
It measures carboxyhemoglobin, the percentage of hemoglobin carrying carbon monoxide instead of oxygen.
Do I need to fast for this test?
No. Fasting is not required for a carbon monoxide blood test.
Why does timing of the sample matter?
Carbon monoxide leaves the bloodstream over hours once exposure stops, so a sample taken soon after exposure gives a more accurate picture of the peak level.
Can smoking affect the result?
Yes. Tobacco smoke contains carbon monoxide, so people who smoke often have higher baseline carboxyhemoglobin levels.
What symptoms prompt this test?
Headache, dizziness, nausea, confusion, and shortness of breath are common reasons, especially when more than one person in a building feels unwell.
Ready to get tested?
Order online and visit a collection site near you, or choose a mail-in kit. No referral and no insurance required.
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