Opioids can cause constipation, which is problems emptying your bowels. Fentanyl may be less likely to cause constipation than morphine.
Your doctor or nurse may give you medicines, called laxatives, to prevent or treat constipation. If you are taking a stronger opioid like morphine, you may need to start taking a laxative straight away – your doctor can advise you about this. It can also help to drink lots of water and try to keep active if possible.