How long does it take for nicotine to be out of your system, after u quit smoking?

Better question:: The more pragmatic question is whether you will benefit from ongoing nicotine replacement. About a third of patients who are tobacco dependent will live longer if they are maintained on nicotine replacement. Serum cotinine levels are the most accurate predictor but clinically if one has or had a history of craving for a cigarette within the first 1/2 hour of awakening - consider replacement.

Varies: Studies cite the half life (time for half to be gone) as 2 hrs and most accept 4 half lives to be when it is gone. However metabolism also slows at lower concentrations to a half life of 11 hrs due to release of some that was bound to tissue. Gender, race and age differences also account for small differences. That said, by a week after abstinence it is effectively gone.