Dilaudid 4mg begins to take effect within 15 to 30 minutes when taken orally, in immediate-release form. The effects are usually felt within one hour, and the pain-relieving effects can last between 3 to 6 hours. If you have specific concerns or are buying Dilaudid 4mg for pain management, always purchase Dilaudid 4mg according to your doctor's guidelines to ensure safe and effective use.