If you have a nicotine test in your blood, you need to stop using nicotine-containing product three days prior to the date of examination. Avoid also the consumption of thiocyanate containing foods, as it can lead to false positive results.
If you're considering a blood tests, nicotine is usually visible 1 to 3 days after last use of a nicotine-containing product like cigarettes or tobacco. But it may also vary in lieu of the amount of nicotine use, the individual’s health and age.