A disposable electronic timer in the form of a disk having a liquid crystal or similar display, adapted to be glued to a medication bottle cap. A lower major surface of the timer has an adhesive layer with a cover that can be peeled off to expose the adhesive so that the timer can be secured to the bottle cap. The upper major surface of the timer contains the timer display and a control button that in one mode starts the timer so that an alarm within the timer sounds after a preset time interval, and in another mode sets or resets the timer to a different preset time interval. Operating power is supplied by a battery within the timer.