Why does chemotherapy cause constipation?

Constipation is a common side effect of some types of chemotherapy. Chemotherapy is a cancer treatment that uses drugs to kill cancer cells, and certain kinds of these drugs can slow down how the bowel works.

Chemotherapy is often not the only reason, though. Many other medicines used during cancer care can also cause constipation, including opioid pain medicines, anti-anxiety drugs, anti-nausea drugs, and diuretics (medicines that remove extra fluid from the body). On top of this, treatment can leave you with less energy for exercise and can change your appetite and diet. Being less active and eating differently than usual can each contribute to constipation.

Because there can be several causes at once, it helps to tell your health care team early if you notice a change in your bowel habits. They can look at your treatment and medicines and recommend ways to prevent or relieve constipation. Your healthcare team is the best source for advice about your specific situation.