Side effects
Constipation
Constipation means having fewer bowel movements than usual, or stools that are hard and difficult to pass. Pain medicines, anti-nausea medicines and some chemotherapy can cause it.
Why it happens
Constipation can be caused by pain medicines (especially opioids), anti-nausea medicines, some chemotherapy, being less active, eating less or drinking less than usual, and sometimes the cancer itself.
What helps
- Drink plenty of fluids, unless your care team has told you to limit them. Warm drinks can help get things moving.
- Add fiber gradually, from fruits, vegetables, whole grains and beans, if your care team says it’s right for you.
- Stay active with short walks or light exercise, as you’re able.
- Ask about stool softeners or laxatives, especially if you take opioid pain medicine. Don’t use enemas or suppositories without checking with your care team first, because they may not be safe when blood counts are low.
When to call your care team
Call if you go two or three days without a bowel movement (or longer than your care team told you to wait), or if you have belly pain or swelling, vomiting, or can’t pass gas.
Questions to ask your care team
Bring these to your next visit, or write down your own.
- Should I take a stool softener or laxative, and which one?
- Is it OK to add more fiber to my diet?
- When should I call you about constipation?
Go deeper
More detailed information
For more clinical detail, our affiliate, Northside Hospital Cancer Institute, covers this topic in depth.
Constipation and cancer treatment (National Cancer Institute)Sources
This page is for general education and does not replace advice from your doctor or care team. Last updated October 26, 2026.