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Cotinine, Serum

Measures cotinine, which your body makes from nicotine. It shows nicotine use or heavy smoke exposure over the last few days.

AI-verified against cited sources. Awaiting expert reviewLOINC 10365-5

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What it is

When nicotine enters your body, the liver turns most of it into cotinine. Nicotine levels fall by half in about two hours, but cotinine lasts for days, so it is a steadier sign of recent exposure. Any source counts: cigarettes, cigars, chewing tobacco, vapes, nicotine gum, patches or lozenges, and heavy secondhand smoke. It is sometimes ordered before surgery, for insurance paperwork, or to check on a quit-smoking plan.

Why it matters

Tobacco smoke raises the risk of heart disease, lung disease and cancer. A cotinine level gives an objective measure of recent nicotine exposure, which can be more reliable than memory. It can help a person and their care team see whether nicotine use has stopped. It also shows how much nicotine reaches someone who lives with heavy smoke exposure.

If it’s high

A high cotinine level means nicotine has entered your body in the last few days. It cannot show which product it came from. Daily cigarette smokers often have levels of about 100 to 250 ng/mL. Exposure to other people's smoke usually stays under 3 ng/mL. Results in between depend on the cutoff your lab or program uses.

Common causes

  • Smoking cigarettes, cigars or a pipe
  • Vaping (cotinine levels in regular vapers are similar to those in cigarette smokers)
  • Smokeless tobacco
  • Nicotine gum, patches, lozenges or pouches
  • Heavy or long exposure to other people's smoke (usually a low level)
  • Smoking cannabis in blunts (hollowed-out cigars), which can give levels like active smoking

What can help

  • If you want to quit, ask your clinician about proven quit-smoking support; in the US, 1-800-QUIT-NOW connects you to a free state quitline
  • If a result surprises you, ask whether secondhand smoke, nicotine replacement or a vape could explain it
  • If the test is for surgery or insurance, ask the ordering office which cutoff it uses and how long to wait after your last nicotine

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: up to 5 ng/mL. Source: ARUP Laboratories, Nicotine & Tobacco Research (SRNT subcommittee on biochemical verification).

SRNT 2019 update: serum or plasma cotinine cutpoints for separating smokers from nonsmokers (research guidance)

  • Below the cutpoint range (secondhand smoke exposure usually falls here)below 3 ng/mL
  • 3 to 10 ng/mL: the range where cutpoints are set3 to under 10 ng/mL
  • Above the cutpoint range10 and above ng/mL

What can affect your result

  • Time since your last nicotine: cotinine falls by half about every 16 hours
  • The amount and type of nicotine you use
  • Genes that control how the liver processes nicotine, which vary across ethnic groups
  • Estrogen, pregnancy and heavy alcohol use, which speed up how the body handles nicotine and cotinine
  • Secondhand smoke exposure
  • Smoking cannabis in blunts, which can raise cotinine
  • The test method (LC-MS/MS or immunoassay)
  • Every nicotine source counts, including cigarettes, cigars, chewing tobacco, vapes, nicotine gum, patches and lozenges. This test cannot tell tobacco from nicotine replacement products.
  • Secondhand smoke can give a low but measurable result.
  • How fast your body clears nicotine varies with genes, ethnic background, sex hormones, pregnancy and heavy alcohol use, so the same use can give different numbers in different people.
  • Methods differ. LC-MS/MS is more specific. Immunoassays often read higher because they are less specific.
  • Use the tube your lab specifies. ARUP rejects serum gel (SST) tubes and light-blue citrate tubes for this test.

Cotinine falls by half about every 16 hours (about 8 to 30 or more, depending on the person), so it reflects nicotine use over roughly the last few days. For a daily user, it usually takes about 80 to 100 hours to drop to common cutoff levels after the last nicotine.

When to talk to a clinician

A cotinine result is never an emergency by itself. Talk with your clinician if you want help quitting, or if you are pregnant or have a child who lives with heavy smoke exposure.

Questions you could ask

  • Would a urine or saliva test suit my situation better than a blood test?
  • Which cutoff does this lab or program use, and what does my number mean against it?
  • If I use nicotine replacement or a vape, how will that show on this test?

Questions people ask

Will vaping, patches or gum show up?

Yes. Cotinine comes from nicotine itself, so any nicotine product raises it. This test cannot tell a cigarette from a patch or a vape. A different urine test that includes anabasine can help show tobacco use, although it is less helpful for vaping because some e-liquids contain traces of it.

How long after I quit will the result be negative?

Cotinine halves about every 16 hours, and the time varies from person to person. For most daily users it reaches common cutoffs in about 3 to 4 days. Experts consider waiting 6 to 7 days after the last nicotine a safe way to avoid a false positive.

Can secondhand smoke cause a positive result?

It can cause a low, measurable result, usually under 3 ng/mL. Heavy or prolonged exposure can go higher. ARUP notes that passive and active exposure cannot be fully separated by this test, so the cutoff your lab or program uses matters.

Show the science and sources

Units

  • 1 ng/mL = 1 ng/mL
  • 1 ng/mL = 1 µg/L
  • 1 ng/mL = 5.675 nmol/L

Open the Cotinine (Serum) unit converter

For clinicians and researchers

Cotinine is the major proximate metabolite of nicotine, formed mainly by CYP2A6, with a mean half-life of about 16 hours (about 8 to 30 or more hours). Serum and plasma cotinine are usually reported as free cotinine. ARUP measures nicotine and cotinine by LC-MS/MS with a 5 ng/mL cutoff each, notes that passive and active exposure cannot be separated definitively, and notes that 10 ng/mL cotinine is often used for surgery clearance. The 2019 SRNT update puts plasma and saliva cutpoints at 3 to 10 ng/mL and urine cutpoints at 30 to 50 ng/mL, with about 80 to 100 hours to fall to the cutpoint after the last nicotine. In NHANES 1999-2004 the optimal serum cotinine cutpoint for US adults was 3.08 ng/mL (sensitivity 96.3%, specificity 97.4%), with race- and ethnicity-specific values from about 0.8 to 5.9 ng/mL, and the older 14 to 15 ng/mL cutoff overestimates the number of nonsmokers. In pregnancy, where nicotine and cotinine metabolism are faster, 5 to 10 ng/mL has been suggested. Daily smokers average about 100 to 250 ng/mL of free serum cotinine, while secondhand smoke exposure is usually under 3 ng/mL. Cotinine cannot separate tobacco from nicotine replacement or e-cigarettes; anabasine and anatabine in urine (cutpoint about 2 ng/mL) come from tobacco, so they help separate tobacco from pharmaceutical nicotine, though some e-liquids contain them too. Total nicotine equivalents are the preferred quantitative marker of daily nicotine intake but have no established cutpoints. Chromatographic methods are preferred over immunoassays, which tend to read higher.

LOINC 10365-5 (primary), 43196-5, 59891-2. Specimen: serum-or-plasma.

Sources

  1. Nicotine and Metabolites, Serum or Plasma, Quantitative (ARUP test code 0092361), ARUP Laboratories
  2. Biochemical Verification of Tobacco Use and Abstinence: 2019 Update, Nicotine & Tobacco Research (SRNT subcommittee on biochemical verification) (2020)
  3. Optimal serum cotinine levels for distinguishing cigarette smokers and nonsmokers within different racial/ethnic groups in the United States between 1999 and 2004, American Journal of Epidemiology (2009)
  4. Cotinine (PubChem compound 854019), PubChem, National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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