The cotinine test is a common biomarker measurement used in health, forensic, and administrative settings to determine a person’s exposure to nicotine. It provides an objective and quantitative assessment of recent use of tobacco products or other nicotine-delivery systems. The test identifies cotinine, a substance produced when the body processes nicotine, making it a reliable indicator of exposure. While the test does not detect nicotine itself, the presence of cotinine is a definitive marker of recent exposure to any nicotine source.
Cotinine as a Nicotine Metabolite
Cotinine is the primary breakdown product, or metabolite, created when the body processes nicotine. After nicotine is absorbed into the bloodstream, it is quickly metabolized, primarily by the liver, into cotinine and other compounds. This chemical transformation makes cotinine the preferred substance for testing nicotine exposure. Nicotine has a short half-life, typically ranging from one to four hours. Cotinine, by contrast, has a significantly longer half-life, ranging from approximately 16 to 40 hours. This longer duration means cotinine remains detectable for several days, providing a more stable and accurate measurement of recent exposure than nicotine testing alone.
Clinical and Practical Applications
The cotinine test is used across medical, administrative, and legal fields. In health and clinical monitoring, physicians use the test to verify compliance with smoking cessation programs. Objective cotinine levels help doctors track a patient’s progress or adjust nicotine replacement therapies. The test is also used to assess health risks in specific patient populations, such as pregnant individuals, where nicotine exposure poses developmental risks to the fetus.
Outside of medical settings, the test is widely applied in insurance and employment screening. Life insurance companies routinely require cotinine testing during underwriting to assess an applicant’s risk profile, which influences premium costs. Employers also use the test as part of pre-employment screening or wellness programs to ensure compliance with policies prohibiting nicotine use. In legal and forensic contexts, cotinine testing determines exposure in disputes over passive or secondhand smoke, providing objective quantification where self-reported status may be unreliable.
Sample Types and Detection Timeframes
The choice of sample type depends on the required detection window and the testing environment. Laboratories utilize different cut-off levels for each sample type, such as 16 nanograms per milliliter (ng/mL) in serum, to differentiate active use from minimal environmental exposure.
Sample Types
- Urine testing is the most common and least invasive method, offering the highest cotinine concentrations and detection for up to three to four days after the last exposure.
- Blood, or serum, testing is highly accurate, providing a precise quantitative measurement. The detection window is usually up to 10 days.
- Saliva testing is a non-invasive and highly sensitive alternative, with a moderate detection window of up to four days following exposure.
- Hair analysis provides the longest detection window, useful for assessing chronic or long-term exposure. This method can detect exposure that occurred up to three months prior.
Sources of Exposure Beyond Tobacco Smoking
While the cotinine test is primarily associated with conventional cigarette use, it detects nicotine exposure from any source. Secondhand smoke, or passive exposure, is a frequent cause of detectable cotinine, though levels are usually below the cut-offs set for active smoking. Nicotine Replacement Therapy (NRT) products, such as patches, gums, lozenges, and inhalers, deliver pure nicotine and will inevitably metabolize into cotinine. A supplementary test for the alkaloid anabasine, found in tobacco but not NRT products, may be used to distinguish between NRT use and continued tobacco consumption.
Modern nicotine delivery systems, including e-cigarettes and various vaping products, also result in a positive cotinine test. These devices deliver nicotine, which the body processes the same way as nicotine from a traditional cigarette. The concentration of cotinine produced depends on the nicotine strength and usage frequency of the device.