Nicotine has a half-life of about two hours and can stay in the blood for about one to three days. Cotinine, a byproduct of nicotine, has a half-life of 18 hours and can last for several days.

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Nicotine quickly enters your bloodstream. Your liver then breaks down nicotine into several byproducts, primarily cotinine. Depending on what you're testing, such as a blood, urine, saliva, or hair ...