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Smoking and Tobacco




For how long the nicotine level can be detected in the blood for a person who use to smoke 3-4 cigarets per day?


Nicotine has a half-life of about 2 hours.  This means that if you have a level of 12 nanograms per milliliter in your body, in 2 hours it will be half of 12 or 6 nanograms per milliliter and 2 hours after that, it will be 3 nanograms per milliliter.  It will be 1 1/2 nanograms per milliter 6 hours after you quit smoking and nearly 0 at about 8 hours.  If you start with more nicotine in your system - for example, 20 nanograms per milliliter, then it takes longer to get to zero. 

The breakdown product of nicotine which is called cotinine - has a longer half-life of about 16 hours.  Depending how high your level is to start with - it may take several days to a week for cotinine, the breakdown product of nicotine, to get to zero. 

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Response by:

Karen L Ahijevych, PhD, RN, FAAN Karen L Ahijevych, PhD, RN, FAAN
Professor Emeritus
College of Public Health
College of Nursing
The Ohio State University