Generally, nicotine leaves your blood 1-3 days after you stop using tobacco, and cotinine (something your body makes after nicotine enters it) will be gone after 1-10 days.
Neither will show up in your urine after 3-4 days. If you smoke menthol cigarettes or breathe in secondhand menthol smoke, cotinine may stay in your pee longer.
A saliva test can detect continine for up to 4 days.
Hair testing can show long-term use of tobacco products. It can be very accurate for as long as 1-3 months after you stop using tobacco and can detect nicotine for up to 12 months.