Consumer Reports News: October 22, 2009 10:34 AM. When the instructions say to take medicine on an empty stomach, how long do I have to wait after eating for my stomach to empty? Can I still drink while waiting? —W.H., Colorado Springs, Colo. For some medicines, having food or liquids in your stomach can result in poorer absorption of the drug or an upset stomach. It generally takes 4 to 5 hours for the stomach to empty after a full meal and a bit less after a snack or liquid, though it varies depending on how much and what kind of food you ate. If you can, it’s easiest to take empty stomach medications in the morning, after you’ve fasted overnight. After taking the drug, wait at least 30 minute before ingesting anything other than plain water, to give the body time to absorb the medication.