How to Manage Constipation: For People With Cancer

What is constipation? 

Constipation is when you have bowel movements (go poo) less often than what is normal for you. Getting constipated is common for people with cancer. 

You may be constipated if:

• your stool (poo) is hard to pass 
• you feel you need to have a bowel movement but nothing comes out
• your stool is small, hard, dry, and looks like pellets

When you are constipated you may also have:

• a stomach ache or cramps
• a bloated belly that feels full or uncomfortable
• a lot of gas or burping 
• nausea (feeling like throwing up) or vomiting (actually throwing up)

When should I talk to my health care team?

Contact your health care team right away if you have any of the following symptoms:

• You have not passed any stool (poo) in more than 3 days
• Bright red blood in your stool
• Very dark or black stool
• You are not able to pass gas 
• Bloating, cramping or pain/discomfort in your stomach 
• Nausea and vomiting (throwing up)

What causes constipation when you have cancer?

Medications are the most common cause of constipation when you have cancer. Some of the medications that cause constipation are:

• opioid pain medications (like morphine)
• chemotherapy medications (like vincristine, vinorelbine)
• medicines for nausea (like ondansetron)
• supplements (like calcium or iron medication)

Some other examples of things that may cause constipation are:  

• changes in your diet
• not drinking enough liquids
• stress, anxiety and depression
• not getting enough exercise or physical activity

What can I do to manage constipation?

Take laxatives

Laxatives are medicines that help you have a bowel movement (go poo).  

You may need to take laxatives:

• every now and then for occasional constipation
• regularly as part of a bowel care routine if you take medication that causes constipation

There are different kinds of laxatives that work in different ways. Your health care team can help you choose the type of laxative that is right for you. 

Laxatives can cause mild stomach cramps. If you get painful cramps or diarrhea, speak to your doctor or pharmacist about whether you should stop taking laxatives.

What is a bowel care routine?

• A bowel care routine is a plan to manage constipation with laxatives.
• Your cancer centre may have a bowel care routine for you to follow if you are taking opioid pain medications.
• If you stop taking laxatives while taking opioids, you will get constipated.

Other things that can help constipation

Drink enough liquids. Liquids help to make your stool soft and easy to pass. Drink at least 6 to 8 cups of liquids each day unless your health care team has told you to drink more or less. If drinking liquids is hard, take small sips often or eat watery fruit, such as melon, pineapple and plums.

Increase the fibre in your diet. To help with mild constipation, you can add more fibre to your diet through food or a soluble fibre powder, such as Metamucil.  It's important to drink more fluids when adding fibre to your diet, to avoid making constipation worse. Check with your health care team before adding a lot of fibre to your diet. People who have had a bowel obstruction or bowel surgery (for example, a colostomy) should not eat a high-fibre diet.

Move your body. Any kind of exercise or movement may help to relieve constipation. Start slowly with light exercise and movement, such as walking. Even 10 minutes a day can help. Stop and rest if you feel pain, nausea or if you have trouble breathing.

Try to relax about using the bathroom. Feeling stress or anxiety about having to poo can make it harder to go. Take your time and try to relax.  

Ask for privacy if you need to. If you can, use the bathroom or commode, instead of a bedpan.

Make a bathroom routine. Try to go to the bathroom around the same time each day. You may find it easier to have a bowel movement first thing in the morning or after a meal.

Get in a better position on the toilet. Put a low footstool under your feet when sitting on the toilet. Do not push hard or strain when trying to pass stool (poo).

Key Points 

• You may need to take laxatives to help manage your constipation.
• If you are taking an opioid medication, you may need a bowel care routine.
• Reach out to your health care team if you have any concerns or questions about managing your constipation.

Where to get more information

The Canadian Cancer Society is a trusted source of information. Visit them at cancer.ca or phone 1-888-939-3333.

For more information on this symptom, or for guides to help manage other symptoms, please see Managing Symptoms, Side Effects & Well-Being.

Ontario Health’s patient guides provide Information on managing health-related symptoms (“Information”). The patient guides are for informational purposes only and are not intended to be a substitute for professional medical advice, diagnosis, treatment, or care. The information does not establish a physician-patient relationship between you and Ontario Health. Always seek the advice of a qualified Health Care Provider.

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This guide was last updated June 2025.