Decorative image

Diarrhoea, constipation and cancer drugs

Diarrhoea, constipation, indigestion and heart burn can all be side effects of taking cancer drugs. Find out more about these side effects and how best to cope with them.

Digestive problems and cancer drugs

Cancer drugs can have various effects on your digestive system.

Some drugs can affect your appetite, or cause diarrhoea or constipation. Some of them may make you more likely to have heartburn (indigestion).

There are many different types of cancer drugs and not all of them will affect your digestive system. 

All drugs have side effects, but not everyone is affected. It is not possible to tell in advance who will have digestive system problems or how bad they might be.

Drug side effects depend on:

  • the drug or combination of drugs you are having
  • the dose
  • how you react to the drug
  • how you have reacted to drug treatment in the past

Make an appointment to see your doctor or specialist nurse if you have changes in bowel movements or are worried about the effects of cancer treatment on your digestive system. There are medicines you can have to help with both diarrhoea and constipation. There are also some things you can do to help yourself.

Coping with diarrhoea

Diarrhoea is a common side effect of some chemotherapy drugs. Some hormone therapies, bisphosphonates or biological therapies can also cause diarrhoea.

With chemotherapy, diarrhoea usually happens in the first few days after treatment. With other drugs it will usually be pretty much as soon as you start taking them. Diarrhoea from some types of chemotherapy can be quite severe.

Remember that you can easily become dehydrated with bad diarrhoea. It is important to drink plenty. If you can't drink enough, or you think you are losing more fluid in diarrhoea than you can replace by drinking, you must tell your doctor or nurse. They can give you tablets to take, to slow down your gut and help control diarrhoea. 

You may also want to ask your nurse about soothing creams to apply around your back passage (anus). The skin in this area can get very sore and even broken if you have severe diarrhoea.


  • Eat less fibre (avoid raw fruits, fruit juice, cereals and vegetables).
  • Drink plenty of liquid to replace the fluid lost from diarrhoea.

Coping with constipation

Painkillers are well known for causing constipation. Bisphosphonates and chemotherapy drugs can also cause it, particularly chemotherapy drugs called vinca alkaloids, which affect the nerve supply to the gut.

Constipation can be worse if you are taking anti sickness drugs and painkillers along with this type of chemotherapy.

Take mild laxatives from the start if you are taking any drugs that are known to cause constipation. You must tell you doctor or nurse if you are constipated for more than 3 days. Constipation is easier to sort out if it is treated early.

It can also help to drink plenty of fluids and eat as much fresh fruit and vegetables as you can. If you can't manage the food, don't worry too much, but make sure that you drink plenty of fluids.


  • Eat more fibre, raw fruits, cereals, fluids and vegetables.
  • Prune juice and hot drinks can help to make your bowels work.
  • You don't have to eat a special diet if you are having chemotherapy, a well balanced diet is all you need.

Coping with indigestion or heartburn

Some cancer drugs can make you more likely to have indigestion. Some may also cause heartburn, which is a burning sensation in the lower chest caused by the back flow of food and stomach acid from the stomach into the food pipe (oesophagus).

Your doctor or nurse can prescribe anti heartburn medicines if you have indigestion or heartburn. You might also need an anti sickness drug.


  • Stop smoking.
  • Limit your caffeine intake from canned drinks, coffee and tea.
  • Lose weight if you are overweight.
  • Raise the head of your bed when sleeping or lying down.
  • Don't eat for 2 or 3 hours before going to bed.
  • Reduce fatty foods in your diet, such as deep fried foods.
  • Avoid foods and drinks that may cause heartburn, such as citrus fruits (oranges, grapefruits), mints and alcohol.
  • Take anti acid or anti sickness medicines as prescribed by your doctor or nurse and let them know if they are not helping.
Last reviewed: 
08 Sep 2017
  • Electronic Medicines Compendium
    Accessed September 2017

  • Handbook of Cancer Chemotherapy (8th Edition)
    R Skeel and S Khleif (Editors)
    Lipincott, Williams and Wilkins, 2011

  • The Chemotherapy Source Book (4th Edition)
    M Perry
    Lippincott, Williams and Wilkins, 2008

Information and help

Dangoor sponsorship

About Cancer generously supported by Dangoor Education since 2010.