People are usually interested in how long nicotine remains in the system because their employer wants to test for nicotine, either as a condition of employment, or more commonly to determine the cost of health insurance.
As unfair as it seems, employers don’t usually distinguish between cigarette smokers and users of nicotine in safer forms, like vaping or smokeless tobacco. Even people who use nicotine gum — which the FDA approves for long-term use — can be treated as a health risk by employers.
Insurance companies consider the presence of nicotine a reliable indicator that the test subject is a tobacco user or a user of nicotine replacement therapy (NRT) products, which usually means an ex-smoker (and someone likely to return to smoking, as more than 90 percent of NRT users do).
But if you try to find the answers to questions like, “How long does nicotine stay in your blood?” or “How long does nicotine stay in your urine?” beware that most testing doesn’t even look for nicotine per se.