How To Stop Diarrhoea Caused By Medication

Diarrhoea (runny poo) is an unpleasant side effect caused by many medicines. In this article, we will discuss the following:

  • What is diarrhoea
  • What medications cause diarrhoea and why
  • What you can do to stop diarrhoea caused by medicines
  • How you can prevent medicine-induced diarrhoea


Diarrhoea usually clears up on its own within 5-7 days, but if your diarrhoea is caused by medication it can take slightly longer.1 To speed this process up, you can avoid certain foods that can make it worse, such as spicy foods, food high in fibre, caffeinated beverages, and ensure you are drinking plenty of water. You can also take anti-diarrhoeal tablets such as loperamide to help control your diarrhoea.9 

Diarrhoea caused by medication

Diarrhoea is categorised as having more than 1 or 2 runny/watery stools per day, or more than usual, and it is most often caused by:1,2

  • A stomach bug, such as C. difficle
  • Norovirus 
  • Food Poisoning

It is also a very common side effect of medication, which it can be quite unpleasant and inconvenient to deal with. The most common type of diarrhoea causing medications are antibiotics.3

Diarrhoea can also be a sign of toxicity associated with some medicines. Diarrhoea can indicate a toxic reaction to digoxin, a medication used for heart problems.3 It can also indicate a toxic reaction to lithium drugs, such as Carbolith.4

It is very important to stay hydrated if you are experiencing diarrhoea. 

What types of medications cause diarrhoea?

Many medicines can cause diarrhoea, and nearly all medications have diarrhoea listed as a side effect. This can be dependent on many factors; a medicine may cause diarrhoea in some people but not in others.3 The dose of your medication can also affect the risk factor of developing diarrhoea.5

The most common diarrhoea-causing medications are:3,4


Antibiotic-associated diarrhoea is one of the most common side effects of antibiotics. Antibiotics can cause diarrhoea because aside from killing harmful bacteria, they also kill the healthy bacteria in your gut that help break down food during digestion. This disturbs the balance of bacteria in your intestines, which causes diarrhoea. Sometimes, a bacteria called C. difficle is able to colonise the intestines when you are taking antibiotics, which can also cause diarrhoea.3


Laxatives are medications used to relieve constipation. They work by loosening your stools. As a result, they may also cause diarrhoea, especially at higher doses. 

Magnesium-containing drugs, such as antacids

Antacids are medications used for heartburn and indigestion. Magnesium can cause diarrhoea by acting like a laxative at high doses, as it is difficult for your intestines to absorb magnesium. As a result, the magnesium attracts water into the colon and creates diarrhoea. This is often accompanied by nausea, abdominal pain, and cramping.5

Cancer treatments

Cancer treatments can be very tough on the body, commonly causing severe side effects. One of the most common is diarrhoea. There are different types of cancer treatments that cause diarrhoea, and the most common are:6

  • Chemotherapy damages the lining of your intestines, causing diarrhoea.
  • Radiotherapy can cause diarrhoea when the radiotherapy is targeting the pelvic area or rectum. 
  • Immunotherapy and targeted cancer therapies can also cause diarrhoea.

Other medications

Signs that you have diarrhoea due to medication

It can be difficult to tell if you have diarrhoea caused by your medication. The number one sign that your diarrhoea is being caused by your medication is that it has come on suddenly after taking it, and your diet and lifestyle have not changed. However, the only way to be sure what is causing your diarrhoea is to consult with your GP or health care provider.

Some of the signs and symptoms of diarrhoea to look out for are:1

  • Runny or loose stools more than 1-2 times per day, or more than usual
  • Dry mouth
  • Abdominal cramps
  • Nausea or vomiting
  • Dizziness
  • Weakness

How to diagnose

It is important to consider other potential causes of your diarrhoea before you can be sure it is your medication causing it. 

Other factors that may be causing your diarrhoea include:1,2

To help diagnose the cause of your diarrhoea, it may be useful to keep a food log. This should also include how much alcohol and coffee/tea you drink. You can also keep a record of your bowel movements. You can give these to your GP at an appointment, and they will review these records and your medical history to help determine the cause of your diarrhoea. 

Ways to stop diarrhoea caused by medication

In most cases, diarrhoea will get better on its own in around 5-7 days.1,2 However, if your diarrhoea is caused by a medicine you will be taking for a long time, you may need to find ways to stop your diarrhoea. 

One way you can stop your diarrhoea is to stop taking the medication causing your diarrhoea. However, please do not discontinue a prescribed medication even if you are certain it is the cause of your diarrhoea until you have consulted with your GP.

Ways to help your diarrhoea at home

To help your diarrhoea clear up quicker you can:7

  • Stay hydrated
  • Avoid foods high in fibre, (wholegrain bread and cereals, nuts, and seeds) as they are harder for you to digest.
  • Avoid spicy or greasy foods 
  • Avoid caffeinated or alcoholic drinks
  • Avoid dairy products if they make your diarrhoea worse

For antibiotic medications, some people have found it beneficial to take probiotics or yoghurt containing probiotics before, during, and shortly after taking a course of antibiotics. Probiotics may be able to help restore and maintain the natural healthy bacteria in the gut and help to prevent diarrhoea. There is not a lot of scientific evidence to support this method, however.8

You can also take oral rehydration solutions. These work by replacing lost fluid, salts and minerals from diarrhoea to treat dehydration.1 The solution contains salts, such as sodium and potassium.

Antidiarrheal medication

There are medications you can take to stop your diarrhoea and reduce the frequency you need to use the toilet. The most common medicine used is called loperamide, sometimes known by its brand name Imodium. This medication is available without a prescription and can be used for short-term diarrhoea relief. It can also be used to treat irritable bowel syndrome (IBS). 

Some people also take loperamide for chronic diarrhoea conditions, such as Crohn's disease or ulcerative colitis.9

Before taking loperamide, it is important to ensure your diarrhoea is not caused by an infection. You can do this by speaking with your GP. Children under 12 should also not take loperamide unless they are prescribed it.1,9


Diarrhoea must be managed efficiently to prevent complications. Otherwise, your diarrhoea can cause:1,2

  • Dehydration 
  • A lack of nutrition
  • Weight loss
  • Salt depletion
  • Skin problems, such as dryness

These symptoms can be problematic in cases of severe and chronic diarrhoea that goes untreated. If you have been experiencing diarrhoea for more than 7 days, or you have bloody stool, please consult with your GP or a healthcare professional.1,2

When suffering from diarrhoea, your body is less able to absorb nutrients. This can cause you to lose weight and become malnourished when you have diarrhoea for longer periods of time. 

As well as your body being less able to absorb nutrients, it can also affect how your body absorbs medications. If your body cannot absorb the medication, it will not work as well. 


The key takeaways from this article are:

  • Diarrhoea is runny or watery poo. It is a common side effect of some drugs including antibiotics, magnesium antacids, and many cancer treatments.
  • It is very important to stay hydrated when you have diarrhoea and seek medical help if you need it.
  • There is no way to prevent diarrhoea caused by your medicines. Do not stop taking your medicine unless you have discussed it with your healthcare provider.
  • Diarrhoea usually goes away on its own but it can be helpful to avoid foods and drinks that can make it worse.
  • Antidiarrheal medications, such as loperamide, are a helpful way to get your diarrhoea under control.
  • Some people find it helpful to prevent diarrhoea by taking probiotics when they are prescribed antibiotics.


  1. NHS inform. Diarrhoea [Internet]; 2021.
  2. NHS. Diarrhoea and Vomiting [Internet]; 2020.
  3. Chassany O, Michaux A, Bergmann JF. Drug-induced diarrhoea. Drug Safety (2000), 22(1):53-72.
  4. Medicines That Can Cause Diarrhea [Internet]; 2021.
  5. Mgbhealth. Why Magnesium Supplements can cause diarrhoea + how to find one that won’t [Internet]; 2021.
  6. Cancer Research UK. Causes of Diarrhoea [Internet]; 2019.
  7. BC Cancer. How to Treat Diarrhea Caused by Your Treatments and Medications [Internet]; 2020.
  8. NHS. Probiotics [Internet]; 2018.
  9. NHS. loperamide [Internet]; 2021.
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Laura Preece

BSc Pharmaceutical Sciences and MRes Pharmacy and Pharmaceutical Sciences
I am a researcher and medical writer with a passion for pharmaceutics, disease and biological sciences. I am currently researching cellular and molecular biology, investigating the use of vitamin C as an adjunctive therapy for diabetes mellitus.

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