What Is Cotinine (COT) on a Drug Test?

Cotinine, abbreviated COT on test panels, is the primary breakdown product your body creates when it processes nicotine. Because cotinine stays in your system far longer than nicotine itself and tracks reliably with how much tobacco or nicotine you’ve actually been exposed to, it has become the standard biomarker that employers, insurers, and healthcare providers use to verify whether someone uses tobacco products. Finding COT on a drug test result means the lab measured cotinine levels in your blood, urine, or saliva to determine your tobacco or nicotine exposure status.

Why Labs Test for Cotinine Instead of Nicotine

Nicotine disappears from your bloodstream quickly, with a half-life of roughly two hours. Cotinine sticks around much longer, with a half-life that typically runs around 16 hours in non-pregnant adults. That longer window gives labs a more stable target to measure. The liver does most of the work, using an enzyme called CYP2A6 to convert nicotine into cotinine and other byproducts.1PubMed Central. Nicotine chemistry, metabolism, kinetics and biomarkers Because cotinine concentrations reflect nicotine intake over a period of days rather than hours, a single sample gives a much more accurate picture of your overall exposure than nicotine alone ever could.

The practical upside for testing is straightforward: a person could abstain from smoking for a few hours and have nearly undetectable nicotine, yet their cotinine level would still clearly indicate recent tobacco use. That makes it much harder to game a cotinine test by simply timing your last cigarette.

Where Cotinine Is Measured

Cotinine can be detected in blood (serum), urine, saliva, and even hair and nails.1PubMed Central. Nicotine chemistry, metabolism, kinetics and biomarkers Each sample type has different strengths, and the choice depends on the context of the test.

For most employment and insurance purposes, you will encounter urine or saliva testing. Blood draws are more common in clinical research settings, and hair analysis tends to show up in epidemiological studies or child welfare investigations rather than standard workplace panels.

Cutoff Levels and What the Numbers Mean

The threshold that separates a “smoker” from a “non-smoker” on a cotinine test depends on the sample type. These cutoffs are not arbitrary; they are statistically derived to best distinguish active tobacco users from everyone else, including people with some secondhand smoke exposure.

A large review of the research found that commonly used cutoff ranges are about 10 to 25 ng/mL for saliva, 10 to 20 ng/mL for serum, and 50 to 200 ng/mL for urine.5PubMed Central. Overview of Cotinine Cutoff Values for Smoking Status Classification One study focused on serum testing identified 10 ng/mL as the optimal cutoff for distinguishing smokers from non-smokers in a clinical setting.6PubMed Central. Accuracy of cotinine serum test to detect the smoking habit and its association with periodontal disease in a multicenter study Meanwhile, the optimal plasma cutoff for the general U.S. population has dropped to about 3 ng/mL, which is much lower than what was used two decades ago. That decline reflects both cleaner indoor-air policies and an increase in light or occasional smoking.1PubMed Central. Nicotine chemistry, metabolism, kinetics and biomarkers

If your result falls below the cutoff, you are classified as a non-smoker or non-user. If it falls above, you are classified as a tobacco or nicotine user. Many insurance and employment tests use a binary pass/fail system rather than reporting a precise number, but the underlying lab work still involves comparing your cotinine concentration to one of these thresholds.

Rapid Strips Versus Laboratory Analysis

You may encounter two very different testing technologies. Point-of-care strip tests, like the NicAlert brand, provide a quick color-coded readout by sorting your cotinine level into broad categories. Laboratory methods using mass spectrometry deliver precise numerical measurements and can distinguish cotinine from closely related molecules. When accuracy matters, the gap between these approaches can be significant.

One comparison study found that while a rapid strip test was 100% sensitive (it caught every true positive), its specificity was only about 38%, meaning it flagged a lot of people as positive who were not actually tobacco users.7PubMed Central. NicAlert™ test strip performance comparison with LC-MS/MS and immunoassay methods for nicotine and cotinine A separate analysis of strip tests in urine reported better specificity at 92% but slightly lower sensitivity at 88%.8PubMed. Use of continine immunoassay test strips for preclassifying urine samples from smokers and nonsmokers prior to analysis by LC-MS-MS Some immunoassay-based tests can also cross-react with a nicotine metabolite called 3-hydroxycotinine, which can push a borderline sample over the threshold even when cotinine itself is low.7PubMed Central. NicAlert™ test strip performance comparison with LC-MS/MS and immunoassay methods for nicotine and cotinine

If you receive a positive result from a rapid test and believe it is wrong, you generally have the right to request a confirmation test by a more precise laboratory method. This is worth knowing, because rapid tests are designed to be sensitive rather than perfectly specific. Their job is to flag potential positives for closer scrutiny, not to serve as final verdicts.

Secondhand and Thirdhand Smoke Exposure

One of the most common concerns people have when they test positive for cotinine despite not using tobacco is whether secondhand smoke could be the cause. The short answer is yes. Cotinine tests detect any nicotine exposure, not just active smoking, and secondhand smoke delivers enough nicotine to register on sensitive assays.

Research on residents of federally assisted housing found that roughly half of non-smoking adults and nearly three-quarters of children and adolescents in those settings showed detectable cotinine from secondhand smoke exposure.9Oxford Academic (Nicotine & Tobacco Research). Cotinine-Measured Secondhand Smoke Exposure Among Federal Housing Assistance Recipients Without Active Tobacco or Nicotine Use in the United States: NHANES, 2007-2018 That is a striking number, but the cotinine levels produced by secondhand exposure are much lower than those seen in active smokers. Most cutoffs are designed to account for this, sorting low-level secondhand exposure below the line and active use above it.

Even thirdhand smoke, the residue left on surfaces and dust in rooms where people have smoked, produces measurable cotinine in non-smokers. A study measuring salivary cotinine found that people exposed only to thirdhand residues had cotinine concentrations about twice as high as unexposed individuals, while people exposed to both secondhand and thirdhand smoke had levels nearly three times higher.10PubMed. Third-hand exposure at homes: Assessment using salivary cotinine These levels are still low in absolute terms, typically well below active-smoking cutoffs, but they illustrate how sensitive cotinine testing can be as a marker of any nicotine exposure.

Can Food Trigger a Positive?

Nicotine is a natural compound found in plants of the nightshade family, including tomatoes, potatoes, eggplants, and some teas. After you eat these foods, small amounts of nicotine get metabolized into cotinine and appear in your urine. An analysis of dietary nicotine estimated that the resulting urinary cotinine concentrations could range from about 0.6 to 6.2 ng/mL, depending on how much of these foods a person consumes.11PubMed. Dietary nicotine: a source of urinary cotinine

Those numbers are low enough that they would not typically trigger a positive on a standard employment or insurance screen using the cutoffs described above. But they could be relevant in research settings that use very low detection thresholds, or in situations where someone’s cotinine level is hovering right near a borderline. If you are a non-smoker who eats a lot of tomato-based foods, the practical risk of a false positive from diet alone is very small but not zero.

Vaping and E-Cigarettes

Because most e-cigarette liquids contain nicotine, vaping produces cotinine just like smoking does. A study comparing urine cotinine levels across different user groups found that exclusive e-cigarette users had a geometric mean urinary cotinine of about 120 ng/mL, which is lower than the roughly 843 ng/mL seen in conventional cigarette smokers but far above the levels of non-smokers, who averaged under 1 ng/mL. People who both vaped and smoked had the highest levels of all, topping 1,000 ng/mL on average.12Tobacco Induced Diseases. Differences between the effects of conventional cigarettes, e-cigarettes and dual product use on urine cotinine levels

This means that if your drug test includes a cotinine panel, vaping nicotine-containing liquids will almost certainly trigger a positive result. Some people assume that because vaping is not “smoking,” it will not show up on a tobacco test. That assumption is wrong. The test looks for the metabolic fingerprint of nicotine, and it does not care how the nicotine got there. Nicotine-free vape liquids would not produce cotinine, but nicotine-free options are a minority of the market, and even some products labeled as nicotine-free have been found to contain trace amounts.

Genetic Variation in How Quickly You Clear Cotinine

Not everyone metabolizes nicotine at the same speed. The liver enzyme CYP2A6, which handles the bulk of the nicotine-to-cotinine conversion and cotinine’s subsequent breakdown, varies considerably across people due to genetic differences. Some individuals carry gene variants that make this enzyme sluggish, and they are classified as “slow metabolizers.” Others have highly active versions and are “fast metabolizers.”

Research in an Alaska Native and American Indian population confirmed that CYP2A6 genetic variants significantly predict how quickly someone processes nicotine.13PubMed Central. Nicotine metabolism and its association with CYP2A6 genotype among Indigenous people in Alaska who smoke Other work has shown that variants in a second enzyme, CYP2C19, also influence how cotinine is further processed, potentially changing the ratio of cotinine to its byproducts in your system.14The FASEB Journal. Assessment of CYP2A6 and CYP2C19 Genetic Variation on Cotinine‐N‐Oxide Formation and their Potential Effect on the Nicotine Metabolic Ratio (NMR)

What this means in practical terms is that two people who smoke the same number of cigarettes can have noticeably different cotinine levels. A slow metabolizer will accumulate more cotinine from the same nicotine dose and take longer to clear it, while a fast metabolizer may test lower despite identical tobacco exposure. Fixed cutoffs handle this reasonably well for most people, but edge cases do exist, especially for light or occasional smokers whose cotinine levels already sit near the threshold.

Pregnancy Changes the Numbers

Pregnant women metabolize nicotine and cotinine substantially faster than they do when not pregnant. Research has found that during pregnancy, the clearance of cotinine increases by about 140% and its half-life drops from roughly 16.6 hours to about 8.8 hours. Even though pregnant smokers in the study consumed similar amounts of nicotine before and during pregnancy, their plasma cotinine levels dropped significantly, from around 202 ng/mL postpartum to about 119 ng/mL during pregnancy.15The Journal of Pharmacology and Experimental Therapeutics. Accelerated Metabolism of Nicotine and Cotinine in Pregnant Smokers

This accelerated metabolism means that standard cotinine cutoffs may underestimate tobacco use in pregnant women. A pregnant smoker could appear to smoke less than she actually does, or a lighter smoker could test below the cutoff entirely. Clinicians who work with pregnant patients need to account for this, and some research settings use lower thresholds when screening this population.

Cotinine Testing in Newborns and Children

Cotinine can cross the placenta, so newborns carry a measurable record of their prenatal nicotine exposure. A study examining dried blood spots from newborns found detectable cotinine in about 35% of samples. Among newborns whose mothers reportedly did not smoke during pregnancy, 29% still had detectable cotinine, presumably from secondhand smoke. About 12% of all newborn samples had cotinine levels high enough to indicate active maternal smoking, yet 41% of the mothers of those infants denied smoking.16Pediatrics. Prenatal Tobacco Exposure and Cotinine in Newborn Dried Blood Spots

Testing infant urine for cotinine can similarly identify ongoing secondhand or thirdhand smoke exposure after birth. A Canadian study of over 2,000 infants found that about 22% had urinary cotinine in a range consistent with moderate secondhand smoke exposure, even in a population where most parents reported not smoking.17Journal of Exposure Science & Environmental Epidemiology. Assessing secondhand and thirdhand tobacco smoke exposure in Canadian infants using questionnaires, biomarkers, and machine learning These findings underscore that self-reported smoking is unreliable, and cotinine testing provides a more honest picture, particularly in pediatric settings where the child cannot advocate for their own exposure reduction.

Cotinine Beyond Pass or Fail

While most people encounter cotinine testing as a simple yes-or-no gatekeeper, the biomarker has broader clinical uses. One growing application involves the nicotine metabolite ratio (NMR), which compares the amount of a downstream metabolite called 3-hydroxycotinine to the cotinine level itself. The NMR serves as a proxy for how fast your body clears nicotine and has been validated as a tool for selecting the best smoking cessation treatment for an individual.18PubMed Central. The Use of the Nicotine Metabolite Ratio as a Biomarker to Personalize Smoking Cessation Treatment: Current Evidence and Future Directions

The logic is that fast metabolizers burn through nicotine replacement therapy (patches, gum, lozenges) too quickly for those products to work well, while slow metabolizers get adequate nicotine levels from the same replacement doses. Studies suggest that for fast metabolizers, non-nicotine medications like varenicline or bupropion are significantly more effective. One analysis found that the number of people who need to be treated to get one additional quitter dropped from 26 to just 5 when fast metabolizers were switched from nicotine replacement to a non-nicotine medication.19Scientific Reports. Characterising the nicotine metabolite ratio and its association with treatment choice: A cross sectional analysis of Stop Smoking Services in England This use of cotinine-derived measurements to personalize cessation therapy is still working its way into routine clinical practice, but the evidence behind it is strong.

Distinguishing Tobacco From Nicotine Replacement

Here is a wrinkle that comes up more often than you might expect: if someone is using nicotine patches, gum, or lozenges as part of a quit-smoking program, their cotinine levels will still be elevated. A standard cotinine test cannot tell whether the nicotine came from a cigarette or from an FDA-approved cessation product. Both produce cotinine through the same metabolic pathway.

To solve this, labs can test for minor tobacco alkaloids called anabasine and anatabine. These compounds are found in tobacco leaf but are not present in pharmaceutical-grade nicotine products. If someone’s urine shows cotinine but no anabasine or anatabine, the nicotine almost certainly came from a replacement product rather than from smoking.20PLoS One. Validation of a LC-MS/MS method for quantifying urinary nicotine, six nicotine metabolites and the minor tobacco alkaloids–anatabine and anabasine–in smokers’ urine Smoking cessation programs that monitor compliance routinely use this approach. If you are on nicotine replacement and worried about testing positive on a tobacco screen, asking whether the lab checks for these alkaloids can clarify the picture.

How Long Cotinine Stays Detectable

Detection windows vary by sample type and individual metabolism. In blood and saliva, cotinine is generally detectable for about three to four days after the last nicotine exposure in regular smokers, though light or occasional users may clear it somewhat faster. Urine testing extends the window slightly, often catching exposure from up to a week prior, because cotinine and its metabolites concentrate in urine over time. Hair testing operates on a completely different timescale: depending on hair length, it can reflect exposure from several weeks to several months ago.

The genetic and physiological factors mentioned earlier, especially CYP2A6 activity and pregnancy status, shift these windows meaningfully. A fast metabolizer might drop below a serum cutoff in two days after a single cigarette, while a slow metabolizer could take four or five days from the same exposure. These differences rarely matter for heavy daily smokers, whose cotinine is replenished constantly, but they can be decisive for the occasional social smoker facing a pre-employment screen.