A person goes through various stages upon quitting smoking, the first of which is accompanied by strong withdrawal symptoms, such as nicotine cravings, insomnia, anxiety, food cravings, drowsiness and irritability. These symptoms usually begin within the first few hours of quitting cigarettes and peak approximately three days into withdrawals.
As the body experiences nicotine withdrawals, it also immediately begins to repair itself in the absence of the drug and the rest of the toxic chemicals contained within cigarettes. During the first few days after quitting smoking, a person's senses of taste and smell begin to return to normal and the risk of heart attack declines. Blood oxygen levels slowly return to normal as the carbon monoxide from past cigarettes clears out of the cardiovascular system. The body's heart rate and blood pressure almost immediately return to a healthy range, and the circulatory systems begins to function more efficiently.
Approximately three weeks after quitting smoking, a person begins to breathe more clearly and is able to regain stamina during physical activities as the lungs regenerate. This is also the time when strong withdrawal symptoms begin to subside. As each new month passes, the body is better equipped to fight infections and the risk of heart disease, stroke and lung cancer diminish greatly.