Dealing with diarrhea and constipation during cancer treatment

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on April 29, 2022.

Gastrointestinal complications such as diarrhea and constipation are common when you’re dealing with cancer. These may be caused by the cancer itself, its treatment or even changes to your lifestyle. But there are things you may be able to do to feel better faster.

Constipation and cancer

If you’re not having regular bowel movements or your stool is hard and difficult to pass, you may be constipated. There are many potential reasons for this, including a tumor in your abdomen or pelvis and certain types of cancer treatments such as opioids for cancer-related pain or chemotherapy.

Other signs of constipation include:

  • Leaking soft or liquid stool
  • Cramping
  • Excessive gas
  • Bloating

Common medications associated with constipation

Some medicines used to treat depression, which may accompany a cancer diagnosis, cause constipation. You may be physically and emotionally exhausted from all that you’re going through and less likely to exercise or eat a healthy diet. Cancer and its treatments may affect your appetite—and changes in diet may also cause constipation.

What to do: Ask your doctor about potential side effects such as constipation when starting a new medication. But remember that risk of constipation isn’t a reason to avoid treatment, as it may be managed.

If you haven’t had a regular bowel movement in three days, tell your care team. They may suggest over-the-counter stool softeners or fiber supplements. Don’t take anything without consulting with your care team first.

When you eat and what you eat may make a difference, too. Eating your meals on a regular schedule may help relieve constipation. Adding more high-fiber foods—such as whole grains, fruits and vegetables—and staying hydrated are known to help reduce constipation. A dietitian may help you set up an eating plan that keeps you strong and regular, and help you make adjustments along the way.

Drinking warm or hot fluids in the morning may help get things in your digestive tract moving. You also should stay active, as exercise is known to help stimulate the digestive system.

Some foods and drinks may increase the chances of becoming constipated or cause gas and bloating, which may worsen symptoms.

If you’re constipated, avoid:

  • Apples
  • Avocados
  • Beans
  • Peas
  • Cabbage
  • Broccoli
  • Milk
  • Carbonated beverages
  • Chewing gum
  • Cheese
  • Eggs

It’s important that you keep your care team informed to make sure you’re doing everything possible to overcome the constipation and feel better.

Remember, these changes aren’t forever. You may resume eating and drinking normally when you’re no longer constipated. Still, it’s a good idea to make sure you’re getting enough fiber and fluids to keep your body running the way it should.

Common medications and treatments associated with diarrhea

Treatment-related diarrhea, or passing watery stools several times a day with or without discomfort, may last up to several weeks or months after treatment ends. It’s important to get a handle on diarrhea as early as possible to avoid dehydration.

Diarrhea may be caused by cancer or its treatments, such as chemotherapy, targeted therapy, immunotherapy, or radiation to the pelvic area. Surgery and other medications may also contribute to diarrhea. Some powerful cancer treatments leave you with a weaker immune system more prone to developing infections that may cause diarrhea.

What to do: Always ask your cancer care team what side effects to expect when starting a new treatment. Risk of diarrhea is no reason to avoid treatment, but being alert to the possibility may help you take steps to prevent it from occurring.

If you’re experiencing diarrhea:

  • A clear liquid diet that includes water, weak tea, clear broth, popsicles and gelatin makes sense initially.
  • Try to drink at least 1 cup of liquid after each loose bowel movement. Water, sports drinks or clear broth are great choices.
  • Don’t reach for acidic juices like tomato or orange juice or carbonated soft drinks. These will likely worsen diarrhea.
  • Getting enough potassium is also important. Bananas or sports drinks are good sources of this mineral, which you may lose when you have diarrhea.
  • It’s also OK to eat crackers and pretzels.

Many medications are available to help with diarrhea, but ask your care team before you take any of them.

Start reintroducing foods slowly once you’re feeling better. Foods that are easy to digest include:

  • Rice
  • Bananas
  • Applesauce
  • Yogurt (low-fat or Greek)
  • Mashed potatoes
  • Low-fat cottage cheese
  • Dry toast

Some of these foods are recommended in the BRAT diet for an upset stomach. BRAT stands for bananas, rice, applesauce and toast. These foods are binding and low in fiber, which may make your stool firmer.

Certain foods and drinks may worsen diarrhea and should be avoided. These include:

  • Milk and other dairy products
  • Pastries and rich desserts
  • Candy
  • High-fat items including fried and greasy foods
  • Alcohol
  • High-fiber foods such as nuts, seeds, whole grains, legumes, dried fruits, and raw fruits and vegetables
  • Sugar-free gum

Although not a food or drink, tobacco should also be avoided.

Recovery may be a gradual process. Be kind to yourself. If you’re getting better after a day or two, try eating small meals again.

Keep your behind comfortable

Diarrhea may leave you feeling inflamed and irritated, especially if it continues for a while. Stay comfortable by using dampened toilet paper or baby wipes to clean yourself. Taking a hip bath and/or applying a water-repellent ointment may also soothe the area.

Call your doctor if:

  • You have diarrhea several times a day for up to four days.
  • There is blood in your stool.
  • You have a fever and new pain and swelling in your abdomen.

It’s also important to be mindful about dehydration. If you haven’t urinated for 12 hours and haven’t been able to consume liquids for a day, contact your care team.

The best things you may do for your health are to follow your care team’s instructions, treat your cancer, be gentle to yourself—and get back to feeling good.

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