How long it takes to take effect after taking ibuprofen depends on the individual’s sensitivity to the drug, and the purpose of treatment. Ibuprofen is a clinically used antipyretic and analgesic drug with the dual effect of antipyretic and analgesic. When used to reduce fever, it can take effect about 30 minutes after oral administration, and the antipyretic effect can last for about 4-6 hours, and can be repeated after 6 hours if necessary, but should not be used more than 4 times in 24 hours. When used as a painkiller, it can take effect about 0.5-2 hours after taking the drug, and the duration of action is about 4-6 hours. As ibuprofen may cause adverse reactions in the gastrointestinal tract, such as stomach pain, nausea, vomiting, indigestion, and even gastric ulcers, and some patients may also experience headache and drowsiness during the course of taking it. Therefore, patients are not recommended to apply ibuprofen for a long time and need to use it under the guidance of professional doctors.