If you have taken the medicine without having food (the stomach is empty), the duration it will make its mark is fifteen to twenty minutes. If your stomach is filled (after a meal), and you take Tylenol, the time it will take to produce effect is half an hour to sixty minutes. Similar to any medicine, it cannot do wonders. Kindly wait and the healing process will fall in place. However, do not take an over dosage to get immediate results. The effects of Tylenol will stay in the body for four to eight hours and on an average, it can stay in the human body for three to six hours.