Nicotine itself leaves your body relatively quickly, but its main byproduct, cotinine, lingers longer and is what most tests actually detect.
Nicotine vs. cotinine: - Nicotine has a half-life of about 2 hours, so it's mostly gone from your blood within about 1–2 days of your last use. - Cotinine (what your body breaks nicotine into) has a half-life of about 16 hours and is what nicotine tests measure, because it stays detectable much longer.
Detection windows by test type: - Blood: Nicotine for 1–3 days; cotinine for up to about 10 days. - Urine: Cotinine typically detectable for 3–4 days in occasional users, and up to 3 weeks or more in heavy, regular users. - Saliva: Cotinine for up to about 4 days. - Hair: Nicotine/cotinine can be detected for up to 90 days or longer, though hair testing is less common.
Factors that affect how long it stays: - How much and how often you used (heavy long-term users clear it more slowly) - Your metabolism, age, and overall health - Kidney and liver function - Hydration and activity level (minor effects) - Genetics (some people metabolize nicotine faster)
What happens in your body after quitting (the encouraging part): - Within 20 minutes: heart rate and blood pressure begin to drop - Within 12 hours: carbon monoxide levels in your blood normalize - Within 2–3 days: nicotine is essentially cleared, and taste and smell begin improving - Within 2–12 weeks: circulation and lung function improve - Nicotine cravings are usually strongest in the first few days to weeks, then gradually decrease
The key takeaway: While nicotine clears your body within a few days, the psychological habit and cravings take longer to fade. Quitting support — nicotine replacement, medications, counseling, or quitlines — significantly improves success.
If you're working to quit, free resources like 1-800-QUIT-NOW (US) offer support and have helped many people succeed.