Common signs and symptoms of diarrhoea

About 1 out of every 10 people with cancer will suffer diarrhoea at some time during their illness. You need to know what is normal for you when deciding whether you have diarrhoea or not. Generally, diarrhoea means

  • An increase in the number of bowel movements you have each day
  • An increase in the amount (volume) of stools you have in a day
  • A change in the way your stools look (they go from solid to soft or watery)

Other symptoms you may notice are

  • Cramping pain in your tummy (abdomen)
  • Feeling sick
  • Needing to get to the toilet urgently
  • A bloated feeling in the tummy

If you have a colostomy or ileostomy and you are emptying your stoma bag more often than normal, then it may be a sign that you have diarrhoea.

Symptoms of severe diarrhoea

If your diarrhoea becomes very severe, you can lose a lot of fluids (dehydration) and this can make you very ill if it isn’t treated. You may have a serious infection that is making your diarrhoea worse.

So it’s important that you see your doctor if you have any of the following symptoms of severe diarrhoea

  • A high temperature (fever) or chills
  • Signs of dehydration such as feeling very thirsty, a rapid heart beat, feeling or being sick, and dark urine
  • Blood or mucus in your stool
  • Severe cramping and tummy pain

When to contact your doctor

Having continuous diarrhoea can make you very dehydrated. This can cause more serious problems. It is very important that you let your doctor or nurse know if you think you are losing more fluid than you are able to drink.

Sometimes it can be hard to know when to call your doctor because you don’t want to bother them. You may feel embarrassed about talking about diarrhoea.

You may worry about what is causing your diarrhoea but it’s better to tell your doctor or nurse as soon as you have the first signs of diarrhoea. They will understand and want to help. They can advise you on how to manage your diarrhoea and may recommend some medicines.

Causes of diarrhoea

Here we tells you about the causes of diarrhoea due to cancer or its treatment. You can find information on the following possible causes

  • Cancer treatments
  • The tumour itself
  • Infections
  • Side effects of drugs
  • Side effects of herbal supplements

Cancer treatments

All cancer treatments have side effects. Diarrhoea can be a side effect of

  • Chemotherapy
  • Radiotherapy
  • Biological therapy
  • Surgery
  • Bone marrow or stem cell transplant

A combination of these treatments can cause more severe diarrhoea.


Some chemotherapy drugs irritate the lining of your digestive system so diarrhoea can be a common side effect of chemotherapy. It usually comes on in the first few days after each treatment.

With some chemotherapy drugs, diarrhoea can be quite severe. Your doctor or nurse will let you know if the drugs you are having will cause diarrhoea. If you have bad diarrhoea, remember that you can easily become dehydrated. So try to drink plenty of water.

If you cannot drink enough, or you think you are losing more fluid in diarrhoea than you can replace by drinking, you must see your doctor or chemotherapy nurse.

If you have diarrhoea after chemotherapy, tell your doctor or chemotherapy nurse. With your next chemotherapy treatment, they can give you tablets to reduce the diarrhoea.

You may also want to ask about soothing creams to apply around your anus. The skin in this area can become very sore and even broken with severe diarrhoea.

There is general information about the side effects of cancer drugs in the treatment section.


Diarrhoea is quite a common side effect of having radiotherapy to the pelvic area or back passage (rectum). But radiotherapy affects people in different ways, so it’s difficult to predict exactly how you will react. You may also have

  • Stomach cramps
  • A lot of wind (gas, flatulence)

Diarrhoea should disappear after a few days, but it can continue for some weeks after your treatment finishes. Apart from being unpleasant, diarrhoea can also make you feel weak and tired. So it’s important to drink plenty of fluids. Otherwise, you can easily get dehydrated.

Remember that you need to contact the radiotherapy department, or your doctor or nurse, if your diarrhoea doesn’t seem to be getting better. You may need anti diarrhoea drugs. Or you may just need advice about making changes to your diet or drinking more.

Biological therapy

Biological therapies are cancer treatments that use natural body substances to attack cancers. Some drugs such as interferon, cetuximab and erlotinib can cause diarrhoea.

The severity of your diarrhoea depends on the particular drug, and the dose, you are having. Let your doctor or nurse know if you have diarrhoea. They will be happy to give you advice or treatment to help manage your diarrhoea.


Sometimes, surgery to your stomach, surgery to your gallbladder or surgery to your bowel or rectumcan cause diarrhoea. This may only be a short term problem. But sometimes it can continue for weeks or months after your surgery.

Your doctor should discuss this with you before your operation. Managing long term diarrhoea can be difficult but there are ways of treating it.

Bone marrow or stem cell transplant

If you have had a bone marrow transplant from a matched donor, you may develop a transplant reaction called graft versus host disease (GVHD). One of the symptoms of GVHD is diarrhoea.

The tumour itself

Some types of cancer, such as bowel cancer, are more likely to cause diarrhoea than others. And some cancers can produce hormones and chemicals that cause diarrhoea. Doctors call this paraneoplastic syndrome.

If you have a very advanced cancer then diarrhoea caused by the cancer itself may be more of a problem. Depending on the cause, your doctor or nurse may be able to prescribe treatment to help control it.


Cancer treatments can weaken your immune system, which means you could get infections more easily. Some types of infection can cause diarrhoea.

Side effects of drugs

Diarrhoea can be a side effect of many types of drugs. These include

  • Some types of antibiotics
  • Drugs given to treat constipation (laxatives)
  • Medicines that contain magnesium, such as some antacid medicines
  • Some anti sickness drugs such as metoclopramide (Maxalon)

If you think you have diarrhoea because of medicines you are taking, let your doctor or nurse know. They will be happy to help with advice or treatment.

Side effects of herbal supplements

Some herbal medicines can cause diarrhoea. These include

  • Milk thistle
  • Ginseng
  • Cayenne
  • Saw palmetto

We have only mentioned a few herbal supplements that may cause diarrhoea. There are many more, so do ask your doctor’s advice before taking any herbal supplements.

Remember that herbal products aren’t necessarily all safe to take. Although they are natural products and you can buy them over the counter at a health shop, some may interfere with your cancer treatment. So it is very important to let your doctor know if you are taking any herbal medicine when you have cancer.

Your body when you have diarrhoea

If you have diarrhoea for long periods of time it can be very distressing. And you can feel very weak and tired. You become dehydrated because food passes quickly through the bowel before your body absorbs the vitamins, minerals and water.

When you have diarrhoea, fluid is also drawn out of the cells in your body into the bowel. The fluid is released in the stool. Losing large amounts of fluid can be dangerous for your body.

Along with fluid, you also lose important minerals from the cells of your body. These minerals are called electrolytes. They include sodium, potassium, and calcium.

The electrolytes must be in a certain balance for the body to function normally. When the electrolytes get out of balance it can be harmful to your kidneys and other organs in your body. The salts in the diarrhoea can also make the area around your anus very sore after a while.

Talking about your diarrhoea

Some people may find it hard to talk about having diarrhoea. You may feel embarrassed or upset by your problem. It’s understandable that you may worry that the diarrhoea means your cancer is getting worse or your treatment isn’t working. These feelings are very natural, but it generally isn’t the case.

Try to remember that your doctors and nurses will be very aware of these likely concerns and are used to talking about them. They will be able to reassure you that your diarrhoea is not affecting your cancer treatment. And they will be able to suggest ways to manage your diarrhoea.

Some people say that diarrhoea is the hardest aspect of cancer treatment to cope with. So it is very important that you get some help.

If you find it difficult to talk with your doctors or nurses, it may help to write down any problems that you have. You can give the list to your doctor or nurse to read. It can also help to have a friend or relative go with you and do the talking.

If you are going for your treatment in an open day unit, you can ask to go into a private room to discuss your diarrhoea. Your doctors and nurses are aware that you will want to talk in private sometimes, so don’t be afraid to ask.

What your doctor will do

Sometimes diarrhoea can be very difficult to control. This often depends on what is causing your diarrhoea. Your doctor will usually be able to prescribe you some drugs to help. And they can give you advice about ways to help yourself.

Before your doctor can decide on how best to treat your diarrhoea, they will need to assess how severe the problem is. They also need to find out what is causing it. They will probably want to ask you lots of questions.

It may seem like a lot to deal with if you are feeling very tired. You probably just want your doctor to give you something to help you feel better and leave you alone. But it is extremely important that your doctor does take the time to assess all aspects of your diarrhoea so you get the right treatment.

Your doctor will examine you and possibly arrange some other tests and investigations.

Questions that your doctor may ask

Replacing fluid loss

You can lose a lot of fluid very quickly when you have diarrhoea. So it is very important that you drink as much as you can. If you lose too much fluid and get dehydrated, your doctor will want to replacefluid and body salts until your diarrhoea stops.

Depending on how severe your diarrhoea is, this may mean having fluids into a vein, through a drip in your arm. If you are able to drink, your doctor may try to replace your fluid and body salts (electrolytes) using drinks containing salts and electrolytes. You can buy these from the chemist, but always talk to the pharmacist first so that they can check which other medicines you are taking and what your symptoms are.

The electrolyte drinks contain sodium, potassium and sugar to help replace what you have lost. They won’t stop the diarrhoea. And it is not clear if they are any better than water or soft drinks in helping you recover. Your doctor can keep a check on your fluid and electrolyte levels by taking regular blood tests.

Medicines to help with diarrhoea

Drugs that help to control diarrhoea are called anti diarrhoeals. There are several different types available from chemist shops without a prescription. But others need to be prescribed by your doctor.

Before you try any over the counter drugs to help with your diarrhoea it is very important that you talk to your doctor or specialist nurse. They will need to find out what is causing your diarrhoea in order to decide on the best drug to help you.

The most common drugs used to help with diarrhoea caused by cancer and treatment are

  • Loperamide hydrochloride (Imodium)
  • Co-Phenotrope (Lomotil)
  • Codeine phosphate

Your doctor or specialist nurse may suggest that you try one or more of these. They work by slowing down the time it takes for food to pass through your digestive tract. The medicines may not get rid of your diarrhoea completely but at least they will help to slow it down.

Your doctor may suggest other drugs. Some of them have complicated names. One group of drugs is called anti muscarinics. These medicines help to relieve tummy spasms and cramping. Hyoscine butylbromide (Buscopan) is one of these anti muscarinic drugs.

Another group of drugs is called somatostatin analogues. These drugs lower the amount of fluid produced by the gut. This helps to stop the body losing water and body salts (electrolytes). They also slow down the time it takes for food to move through your digestive tract. Octreotide is a somatostatin analogue that your doctor may prescribe.

If diarrhoea is a known side effect of your cancer treatment, your doctor or nurse may give you anti diarrhoeal drugs to take home with you after your treatment. If your diarrhoea does not get better with these anti diarrhoeal drugs, you should let your doctor or nurse know as soon as possible. They can then suggest an alternative treatment.

To manage a side effect such as diarrhoea, your doctor may change the dose or schedule of your cancer treatment until your diarrhoea is better. This may mean having a break from radiotherapy for a few days or lowering the dose of chemotherapy drugs.

Side effects of anti diarrhoeal drugs are not common, but they can happen. Tell your doctor if any of these symptoms are severe or do not go away

  • A dry mouth
  • Dizziness
  • Drowsiness
  • Vomiting
  • Stomach pain, discomfort or swelling
  • Constipation
  • Tiredness (fatigue)

It is rare, but possible, to have an allergic reaction to one of these drugs. If you come up in itchy lumps, like a nettle rash, or you have sudden wheezing, you could be having an allergic reaction. If you have any of these signs, you need to go to a hospital straight away.

What to ask your doctor about diarrhoea
Some questions you might ask your doctor

  • What is causing my diarrhoea?
  • Are my cancer treatments causing diarrhoea?
  • Are there any medicines that I can take to help reduce the diarrhoea?
  • What if the drugs don’t help me?
  • What can I do to help control diarrhoea?
  • What types of food or drinks should I have?
  • Who can I talk to about my diarrhoea?
  • Can you arrange for me to get pads or a commode from the district nurses?
  • Are there any creams that would help with soreness?