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Diarrhea During Cancer Treatment: Care Instructions


Diarrhea is a common problem for people getting cancer treatment.

Diarrhea can be caused by:

  • Some medicines that damage the lining of your intestines.
  • Radiation therapy aimed at your belly or pelvis.
  • Surgery to remove part of your intestines.
  • A side effect of bone marrow transplants called graft-versus-host disease.
  • Some infections that affect your bowels.
  • Severe constipation. Sometimes when you get really constipated, watery stool is the only stool that can get past the hardened stool.

Some types of cancer, such as colon cancer, can cause diarrhea directly. Plus, the stress of having cancer can lead to diarrhea.

Diarrhea from cancer treatment may be just a minor problem or a sign of more serious problems. Always tell your doctor if you have diarrhea, especially if you see blood in it. Changes in your diet may solve the problem. Your doctor may prescribe medicine if your diarrhea is severe.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

How can you care for yourself at home?

  • Before you take any type of over-the-counter medicine, tell your doctor that you are having diarrhea. If your doctor prescribes diarrhea medicines, take them exactly as directed. Call your doctor or nurse advice line if you have any problems with your medicine.
  • Drink plenty of fluids to prevent dehydration. Take frequent sips of water and other fluids until you feel better, unless you have been told to restrict or limit your fluids. Try water, milk, milk alternatives, broth, or rehydration drinks.
  • Eat 5 to 6 small meals and snacks throughout the day instead of eating 3 big meals. When your gut is feeling unwell, large amounts of food at one time may cause more discomfort. Try to eat a small meal or snack every 2 to 3 hours during the day.
  • Choose foods with soluble fibre. Soluble fibre may help your diarrhea by making your stools thicker. Foods with soluble fibre include:
    • soft, cooked vegetables or fruits with the skins and seed removed
    • peeled apples or applesauce, bananas, avocado, and potatoes and sweet potatoes with skin removed
    • barley, oatmeal, or oat bran
    • psyllium fibre supplements (talk to your doctor to ask if a soluble fibre supplement is right for you)
  • Limit or avoid certain foods and fluids that may make your diarrhea worse by moving quickly through your gut. During treatment, limit or avoid:
    • sugar-sweetened drinks, such as pop, juice, and energy drinks
    • spicy, oily, or fried foods, such as hot sauce, chilies, and any deep-fried foods
    • caffeine and alcohol, including coffee, tea, colas, and energy drinks. Try drinking decaffeinated coffee and tea instead. Avoid alcohol completely while you have diarrhea.
  • If you have lactose intolerance (gas, bloating, or diarrhea after consuming dairy), limit dairy to what you can tolerate. Dairy products do not cause digestive problems for everyone. If you ate or drank dairy products with no symptoms before experiencing your diarrhea, you can continue to consume them.
    • Only avoid or limit dairy products if you get diarrhea within about 30 to 60 minutes of eating them.
    • Store-bought nutrition supplement drinks are suitable for people with lactose intolerance.
  • Rest when you feel tired.

When should you call for help?

Call 911 anytime you think you may need emergency care. For example, call if:

  • You passed out (lost consciousness).
  • You pass maroon or very bloody stools.

Call your doctor or nurse advice line now or seek immediate medical care if:

  • You are vomiting.
  • You have new or worse belly pain.
  • You have a fever.
  • You cannot pass stools or gas.
  • You have new or more blood in your stools.

Watch closely for changes in your health, and be sure to contact your doctor or nurse advice line if:

  • You have new or worse symptoms.
  • You are losing weight.
  • You do not get better as expected.

Where can you learn more?

Go to

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