Withdrawal refers to the physical problems and emotions you experience if you are dependent on a substance (such as alcohol, prescription medicines, or illegal drugs) and then suddenly stop or drastically reduce your intake of the substance.
Symptoms of withdrawal are caused by decreased amounts of alcohol or drugs in the blood or tissues of a person who has grown accustomed to prolonged heavy use and who then suddenly stops. Withdrawal syndrome is a set of symptoms that occur when you decrease or stop drinking or using drugs after using alcohol or drugs for a long time.
Symptoms of alcohol withdrawal may begin from 4 to 12 hours after you cut down or stop drinking, or as long as several days after the last drink, and can last a few days. They can range from mild to life-threatening.