Depends on what you drank and how much, if you had 3 or four beers it would be out of your system before morning, if you drank "hard" liquor, whiskey, brandy, etc. Then it may take longer. Your body rids itself of alcohol by urine and the moisture in your lungs when you breathe, that's why you can tell almost immediately if someone has been drinking, you can smell them a"mile" off.
