Approved by the Cancer.Net Editorial Board, 03/2017

Diarrhea involves frequent, loose, or watery bowel movements, also called stools. Diarrhea may also be needing to have a bowel movement more often than usual. The usual number of bowel movements you have in a day may be called your “baseline.”

If you experience diarrhea during cancer treatment, ask your health care team about ways to manage it. Relieving side effects is an important part of cancer care and treatment. This is called palliative care or supportive care.

Causes of diarrhea

Causes related to cancer and cancer treatment include:

  • Chemotherapy

  • Immunotherapy

  • Cancer that affects the pancreas

  • Radiation therapy to the pelvis

  • The removal of a portion of the bowel

  • Graft-versus-host disease, a side effect of bone marrow transplantation

These conditions unrelated to cancer may cause diarrhea:

  • Irritable or inflammatory bowel disease

  • Viral infection

  • The inability to digest certain foods

  • Infection with Clostridium difficile, a diarrhea-causing bacteria

  • Antibiotics

Your health care team may perform medical tests to find out what is causing diarrhea.

Grades of diarrhea

Doctors use grades established by the National Cancer Institute to describe the severity of diarrhea:

Grade 1. This is an increase from a patient’s own baseline of less than 4 stools a day.

Grade 2. This is an increase from patient’s own baseline of 4 to 6 stools a day.

Grade 3. This may require treatment in the hospital or clinic. It is characterized by several factors:

  • An increase of 7 or more stools a day.

  • An inability to control bowel movements, known as incontinence.

  • A reduced ability to care for your daily needs.

Grade 4. This is a life-threatening condition that requires immediate intensive care.

Risks of diarrhea

Although uncomfortable, mild diarrhea usually does not cause serious problems. However, severe diarrhea can cause dehydration and imbalance of electrolytes. This happens when the body loses too much water. It may also cause other health problems that can be avoided by preventing diarrhea or treating it early.

Prevention and treatment of diarrhea

The best prevention and treatment options depend on your symptoms and the cause of diarrhea.

Ask your doctor about medicines to prevent diarrhea. These include loperamide (Imodium) and diphenoxylate and atropine (Lomotil). You may receive these for diarrhea caused by chemotherapy. Drugs for diarrhea caused by radiation therapy to the pelvic area are being studied but have not been approved by the U.S. Food and Drug Administration.

Consider these options to help you manage mild diarrhea:

  • Avoid caffeine, alcohol, dairy, fat, fiber, orange juice, prune juice, and spicy foods.

  • Avoid medicines such as laxatives, stool softeners, and metoclopramide (Reglan). Metoclopramide is used to prevent nausea and vomiting from chemotherapy.

  • Eat small, frequent meals and choose foods that are easy to digest. These include bananas, rice, applesauce, and toast. If chemotherapy caused the diarrhea, your doctor may recommend a low-residue diet, which includes low-fiber foods

  • Drink water and other clear liquids to prevent dehydration. People with severe dehydration may need to receive intravenous (IV) fluids. This means that a health care provider gives fluid to the body through a vein.

    If diarrhea is from the pancreas not working well, replacing pancreatic enzymes may help. This occurs in some patients with pancreatic cancer.

  • For severe diarrhea from chemotherapy, ask your doctor about changing the schedule or dose of chemotherapy.

Related Resources

Side Effects of Chemotherapy

Side Effects of Immunotherapy

Side Effects of Radiation Therapy

More Information

National Cancer Institute: Diarrhea

ASCO answers; Diarrhea

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