Smoking and Nicotine in blood

Dear Ask The Doctor: How long does nicotine stay in your system for

Dear Alexander: Nicotine usually has a half life of 2 hours . Half life is the amount of time it takes for a certain substance to loose half of its range of activity. Thus the total duration of how long nicotine stays in the system depends upon the amount inhaled/ number of cigarettes smoked as you are continuosly supplying the body with nicotine thus leading to accumulation, thus prolonging the time for which nicotine stays in the blood. The nicotine in the blood is mainly metabolised by the liver and to some extent the kidney.