Carbon Monoxide in Blood (Carboxyhemoglobin)

Why This Test Might Be Ordered

Your healthcare provider may order this test if you’ve been exposed to smoke, vehicle exhaust, or industrial fumes. It’s also used in cases of suspected carbon monoxide poisoning, especially in smoke inhalation or occupational settings. Some hospitals check newborns for CO exposure during delivery.

What to Expect Before the Test

No special preparation is needed. You’ll likely have a small needle inserted into your arm to draw blood. If you’re a smoker or have recent exposure to carbon monoxide, your provider may discuss this with you beforehand.

What the Results Mean

High levels of carbon monoxide in your blood can block oxygen from reaching your organs. Mild exposure may cause headaches or dizziness, while severe exposure can lead to unconsciousness or even death. Your provider will interpret results based on your symptoms, exposure history, and overall health.

Common Causes of Abnormal Results

Elevated carbon monoxide levels can result from smoking cigarettes, pipes, or cigars; exposure to vehicle exhaust; heating systems with poor ventilation; or industrial environments. Natural sources like certain plants (e.g., some mushrooms) can also contribute, though this is rare.