Nicotine typically has a half-life of about 1 to 2 hours in the body, meaning that half of the nicotine is metabolized and eliminated within this time frame

. After smoking or using nicotine products, nicotine itself is usually cleared from the bloodstream within 1 to 3 days

. However, nicotine is metabolized into cotinine, a more stable metabolite with a longer half-life of around 16 to 20 hours, which can remain detectable in the body for up to 10 days or more depending on individual factors such as metabolism and frequency of use

. Detection times vary by the type of test and body fluid:

• Urine: Nicotine can be detected for at least 3 days, while cotinine can be detected for up to 10 days or longer in regular smokers

• Blood: Nicotine clears in 1 to 3 days, cotinine up to 10 days

• Saliva: Nicotine can be detected up to 4 days, cotinine also for several days

• Hair: Nicotine and its metabolites can be detected for weeks or even months, but hair tests may reflect exposure to secondhand smoke as well

In summary, nicotine leaves the bloodstream relatively quickly within a few days, but its metabolite cotinine can remain in the system for about one to two weeks, making it the preferred marker for testing nicotine exposure. The exact clearance time depends on factors like how much and how often nicotine was used, metabolism, and the type of test employed

. Withdrawal symptoms generally begin within hours after the last use and can last for weeks, even after nicotine has mostly cleared from the body