Approved by the Cancer.Net Editorial Board, 12/2019

Constipation happens when stools become less frequent, painful, or dry and difficult to pass. Constipation starts when the body absorbs more water or signals food to move through the bowels more slowly. It is a common but controllable symptom for people with cancer.

Symptoms of constipation

In addition to not being able to empty the bowel, 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

Your health care team can help you manage the symptoms of constipation. Relieving side effects, also called palliative care, is an important part of cancer care and treatment.

It’s also important to talk with your health care team if your symptoms are new or changing. Constipation can be a sign of a more serious problem and you may need more tests.

Causes of constipation

Common causes of constipation for everyone include:

  • Not eating enough food with fiber

  • Not drinking enough water or other fluids

  • Not exercising

For people with cancer, your treatment may be causing constipation. Pain medicine slows down muscles in your digestive tract, making it more difficult to pass your stool. Iron supplements, chemotherapy, and other drugs that are used to treat nausea, vomiting, seizures, depression, diarrhea, or high blood pressure can also affect your digestion.

In addition to the medication you're taking during cancer treatment, people with cancer may have other causes of constipation:

  • Scar tissue from surgery or cancer growing in the bowel, which can narrow or partially block your bowel

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

  • Cancer pressing on the spinal cord

  • High levels of calcium in the blood, called hypercalcemia

  • Low potassium levels

  • Thyroid gland 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 digestive tract. These tests also help find out if there is hard stool in your rectum.

During your exam, your health care team may ask you about your bowel habits and how they have changed, what medicines you're taking, your diet, and any other illnesses.

Managing constipation

It is very important to treat constipation properly. Without treatment, constipation may damage your intestine or rectum. It can lead to dehydration, block your bowel, and may slow your body's absorption of medicine. If there is scar tissue or a tumor causing the problem, you may need to have more tests and treatment.

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 the medicine that may be causing the 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.

  • Be more active.

  • Use a laxative, an enema, or a rectal suppository. Talk to your health care team first because some of these may be harmful.

Related Resources


Exercise During Cancer Treatment

Side Effects of Chemotherapy

More Information

National Cancer Institute: Gastrointestinal Complications

National Cancer Institute: Constipation and Cancer Treatment

American Cancer Society: Constipation

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.