As with many drugs, the body builds up a tolerance to
nicotine, NIDA points out. Smokers start to need more nicotine to get the same effect. They usually end up smoking more often to get that same nicotine high. Nicotine tolerance builds up quickly over the course of the day during continuous smoking.
People experiencing nicotine withdrawal are often irritable, have a hard time sleeping and difficulty paying attention or thinking clearly. They also often end up with a huge appetite and intense longing, or craving, for a cigarette. The physical symptoms of nicotine withdrawal eventually lessen over time, frequently disappearing altogether after several weeks without nicotine. Cravings for a cigarette, however, can last a lifetime.