How Long Nicotine Stays in Your System

Two different questions hide inside this one. How long does the nicotine itself last in the body? And how long can a test tell that you used it? The answers are hours for the first and days for the second.

Nicotine versus cotinine

A 2019 update by tobacco research scientists, published in Nicotine & Tobacco Research and available as an NIH-funded author manuscript, says nicotine has a relatively short half-life of about 2 hours. A half-life is the time it takes for blood levels to fall by half, so after four half-lives about 6% remains. Because nicotine clears so quickly, the authors call it not very useful as a quantitative indicator of how much someone has taken.

Tests therefore usually look for cotinine, the major breakdown product of nicotine. The same update says the half-life of cotinine can vary from 8 to 30+ hours because of genetic, hormonal and other factors. A separate 2016 review in the Journal of Clinical and Diagnostic Research gives a similar range, calling the half-life long at 15 to 40 hours. It explains that cotinine forms when the liver enzyme CYP2A6 oxidizes nicotine.

How long until a test comes back negative

The update works through an example. Starting from a blood cotinine level of 200 ng/mL, it takes five half-lives to fall below 5 ng/mL.

Cotinine half-life	Time to reach the 5 ng/mL cutoff
8 hours	about 40 hours
16 hours	about 90 hours
30 hours	about 150 hours

A person with a short half-life could fall below the cutoff in about 2 days. Because the half-life is not known in advance, the authors say it is reasonable to allow 6 to 7 days to confirm non-smoking and avoid false positives. The window also depends on how much a person used before stopping and on the cutoff the lab applies.

Which fluids are tested

Cotinine can be measured in blood (serum, plasma or whole blood), saliva and urine. The 2016 review adds that urinary cotinine concentrations are about four to six times higher than those in blood or saliva, which is why urine tests can pick up lower exposures. It also notes that cotinine levels are directly proportional to the amount of nicotine absorbed.

We did not find an official source that gives a detection window for hair, so we do not give one.

What this means if you are quitting

The same markers show nicotine use from any product. The update says nicotine is a highly specific biomarker of use of tobacco products, e-cigarettes and nicotine replacement products, all of which deliver nicotine. If a test matters for a job, an insurance form or a clinical program, ask the lab or the requester which marker and cutoff apply.

The timeline for how you feel is different from the timeline for what a test shows. Health Canada says withdrawal symptoms appear within one to two days, peak in the first week and last about 2 to 4 weeks. For the milestones, see what happens when you quit smoking, and for aids that ease withdrawal see quit-smoking medications.