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Cotinine is a metabolite of nicotine and is used to measure one's exposure to tobacco products. It is most commonly tested for in urine and blood, and most often in urine since that test in non-invasive.
A non-smoker has levels of less than 1 ng/mL. In blood a level less than 10 ng/mL and in urine <11 ng/mL is considered non-smoking. It takes about 2 weeks after the last smoke for cotinine levels to fall to near normal levels in a blood test. Since cotinine remains in urine much longer, it can take several weeks for it to be normal after completely stopping.
How many cigarettes one smokes does matter, since the higher the number the higher the cotinine levels will be. Only with no smoking at all will one accomplish the levels of a non-smoker and it will take a minimum of 2 weeks for a blood test and 4-6 weeks of complete non-smoking for a urine test.
Not only how many cigarettes, but also the type of cigarette (high versus low nicotine, menthol versus non-menthol), how deeply one inhales, and even their genetic make-up contribute to the overall time it takes to reach non-smoking levels.
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