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Smoking & Carboxyhemoglobin

By Cheryl Jones ; Updated August 14, 2017

The effects of smoking on the lungs and heart are well-publicized. Perhaps less well-known is the effect cigarette smoking has on the blood. Cigarette smoke is laden with harmful chemicals, including carbon monoxide. At high levels, carbon monoxide can cause suffocation. In lower concentrations, carbon monoxide prevents the blood from properly transporting oxygen to organs and tissues.

Carbon Monoxide

A carbon monoxide molecule consists of one oxygen atom bound to a carbon atom. Carbon monoxide is odorless, colorless and tasteless. The gas is produced by combustion engines, faulty gas stoves or furnaces, fires, and burning charcoal, notes the website Carbon monoxide is also present in cigarette smoke. The gas is poisonous, warns the Occupational Safety and Health Administration. Warning signs of carbon monoxide poisoning include headache, nausea, dizziness and irritability. Carbon monoxide can lead to loss of consciousness and asphyxiation.


Carbon monoxide has an especially high affinity for hemoglobin, the oxygen-carrying component of blood, explain A. Light and colleagues in their study of carboxyhemoglobin in smokers and nonsmokers published in “Respiratory Care Journal.” The affinity of carbon monoxide for hemoglobin is 245 times higher than the affinity of carbon dioxide. Carboxyhemoglobin forms when carbon monoxide binds to hemoglobin. Because carbon monoxide has such a strong attraction to hemoglobin, the bond is irreversible. Carboxyhemoglobin is unable to carry oxygen to the tissues and organs.

Effects of Smoking

People who smoke cigarettes have a higher level of carboxyhemoglobin compared with nonsmokers, Light and colleagues report. Whereas carboxyhemoglobin levels among nonsmokers are less than 1.5 percent, levels in smokers range from 3 to 15 percent, depending on the number of cigarettes smoked daily. Light also found that carboxyhemoglobin levels of nonsmokers rose when they were exposed to secondhand smoke.


To compensate for the increased levels of carboxyhemoglobin and reduced oxygen levels in the blood, smokers tend to have higher total hemoglobin levels than nonsmokers, according to a study reported in the “Journal of the American Medical Association,” headed by Dale Nordenberg. The increased hemoglobin levels can mask anemia and other medical conditions that are diagnosed based on hemoglobin threshold levels.


Elevated carboxyhemoglobin levels lead to lower exercise tolerance and an increased incidence of heart attacks during exercise, report Nordenberg and colleagues. Conditions such as iron or other nutritional deficiencies, chronic diseases, malignancies, or inflammatory conditions, which are based on hemoglobin threshold levels, may remain undetected and untreated. Once smokers quit the habit, carboxyhemoglobin levels decrease and total hemoglobin levels return to the levels seen in nonsmokers.

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