Approved by the Cancer.Net Editorial Board, 10/2018

Constipation occurs when a person has a feeling of needing to move the bowels but cannot. It starts when the body absorbs more water or signals food to move through the bowels more slowly. Constipation is a common but controllable symptom for people with cancer.

Symptoms of constipation

In addition to not being able to empty the bowels, people with constipation may experience the following symptoms:

  • Pain and cramping

  • Swelling in the abdomen

  • Appetite loss

  • Nausea and vomiting

  • Not being able to urinate

  • Confusion

Talk with your health care team about any constipation symptoms you experience. This includes any new symptoms or a change in symptoms. Relieving side effects is an important part of cancer care and treatment. It is also called palliative care or supportive care.

You can often control these symptoms by taking some simple steps. But these symptoms are sometimes a sign of a more serious problem that means you need more tests.

Causes of constipation

Common causes of constipation include:

  • Not eating enough food or fiber

  • Not drinking enough water or other fluids

  • Not exercising

For people with cancer, the following factors might also cause constipation:

  • Medicines, including:

    • Pain medicines, which can slow the muscular action of the bowel that helps move food through the system

    • Some drugs that treat nausea and vomiting, seizures, depression, diarrhea, or blood pressure

    • Iron supplements

    • Chemotherapy

  • Scar tissue from surgery or cancer growing in the bowel, which causes narrowing or partial bowl obstruction

  • A tumor or scar tissue completely blocking the bowel, called a bowel obstruction

  • Being physically inactive

  • Cancer pressing on the spinal cord

  • High levels of calcium in the blood

  • Low potassium levels

  • Thyroid problems

  • Diabetes

Diagnosing constipation

If you have constipation, your doctor may recommend a rectal examination or an x-ray or other imaging scans. This is to make sure you do not have a tumor blocking your rectum or GI tract. These tests also help find out if there is hard stool in your rectum.

Your health care team may also ask you about:

  • Your bowel habits, before the cancer and now

  • Use of medicines that may cause constipation

  • What you have been eating and drinking recently

  • Other diseases or illnesses

Managing constipation

It is very important to treat constipation properly. Without treatment, constipation may cause internal damage to the intestine or rectum, dehydration, or bowel obstruction. It can also slow the body's absorption of medicines taken by mouth. If there is scar tissue or a tumor causing the problem, you may need to have more tests.

Talk with your health care team about the best way to manage constipation. Some of the following suggestions may help:

  • Drink more liquids.

  • Ask your health care team about changing the dose or stopping medicines that cause constipation.

  • Eat more fiber or take fiber supplements. But if you have scar tissue or a tumor narrowing your bowel, your doctor may recommend a low-fiber diet. This is because the fiber may back up behind the narrower areas of the bowel. A low-fiber diet is also called a low-residue diet.

  • Increase physical activity, if possible.

  • Treatment, such as laxatives, an enema, or a rectal suppository. Some of these may be harmful for some people so talk with your health care team before using any of these treatments.

Related Resources


ASCO answers; Constipation

Download ASCO's free 1-page fact sheets on Constipation. This printable PDF offers an introduction to constipation, including the causes, risks, prevention, and treatment options. A tracking sheet on the back helps record when and how often constipation occurs. Order printed copies of this fact sheet from the ASCO Store.