Ibuprofen typically starts to work within 20 to 30 minutes after taking it by mouth. Maximum pain relief effects commonly occur within 1 to 2 hours. The pain-relieving effects usually last about 4 to 6 hours. If ibuprofen is used for inflammation-related conditions, it may take several days or even a couple of weeks for full relief. Taking ibuprofen on an empty stomach can make it work faster, while food may slow the absorption but does not reduce its overall effectiveness. For topical forms like gels or patches, it can take a day or two to start relieving pain.