It takes about 15-20 minutes after taking ibuprofen to take effect. Ibuprofen is an anti-inflammatory drug of antipyretic and analgesic type, which is comparable to aspirin in composition. It can be used for both pain relief and fever reduction, and is often used for headache and fever caused by cold and flu, etc. Generally, it takes about 20 minutes after taking the drug to have an effect. Because ibuprofen is first absorbed into the stomach through the veins of the stomach, through the portal vein and the liver, and then it can enter the whole body to exert its pain-relieving effect. It is best to take ibuprofen after eating, because taking ibuprofen on an empty stomach may cause damage to the gastric mucosa, which may lead to stomach ulcers or bleeding in the stomach, etc.