Get to grips with diarrhoea

Have you ever wondered why your stomach suddenly decides to turn cartwheels, forcing you into a frantic sprint for the nearest toilet? Or perhaps you’ve found yourself nervously planning your day around public toilets, wondering what on earth is going on inside your gut. You’re not alone.

We’ve all got guts. Around 25ft of them, in fact. That’s a lot of digestive system to keep running smoothly, and when things go wrong, it can disrupt your daily life.

In this post, we’re getting to grips with diarrhoea. From what is actually happening in your gut to the common causes, red flags to look out for, and how you can manage symptoms, we’ll be exploring how you can get your gut back on track.

Please note that this is general information on diarrhoea. The information may not be appropriate for someone diagnosed with a specific digestive condition. Where there is information on digestive symptoms and conditions, more details can be found in our online information.

What is diarrhoea?

Diarrhoea is a very common symptom, characterised by passing looser or waterier poo more frequently than is normal for you. While everyone’s bowel habits are different, ranging from three times a day to three times a week, a sudden change towards frequent, unformed or liquid poo is a clear sign of diarrhoea.

Diarrhoea is generally categorised into two main types based on how long it lasts:

• Acute diarrhoea: This comes on suddenly and usually resolves within a few days to a couple of weeks. It is extremely common and usually caused by a transient infection.
• Chronic (or persistent) diarrhoea: This is diarrhoea that lasts for more than four weeks. Persistent diarrhoea is less common and often points to an underlying digestive condition that requires medical investigation.

What happens in your digestive system during diarrhoea?

To understand diarrhoea, it helps to look at how your bowel usually works. As digested food moves from your stomach into your small intestine, then into your large intestine (colon), your body absorbs nutrients and water. By the time waste reaches the end of the bowel, most of the liquid has been absorbed, leaving behind a well-formed poo.

When you have diarrhoea, this finely tuned process gets disrupted in one of a few ways:

1. Increased motility (rapid transit): The muscles in your bowel wall contract too quickly, pushing waste through the colon before it has time to absorb the fluid properly.
2. Decreased absorption: The lining of your intestine becomes irritated or damaged, preventing it from absorbing water and nutrients back into your body.
3. Increased secretion: The intestine actively pumps extra fluid and salts into the bowel, diluting the poo and making it loose and watery.

What are the common causes of diarrhoea?

Diarrhoea isn’t a digestive condition in itself, but a digestive symptom of something else going on in your body. The causes can range from short-term bugs to long-term health conditions.

Short-term (acute) causes:

• Gastroenteritis (tummy bugs): Bacterial, viral or parasitic infections are the most common culprits. Viruses like norovirus or rotavirus, or bacteria such as Salmonella or Campylobacter (often from contaminated food or water), cause inflammation in the gut lining.
• Dietary triggers and food intolerances: Eating very spicy, greasy or high-fat foods can speed up transit time. Consuming large amounts of artificial sweeteners (like sorbitol) can also draw excess water into the bowel.
• Medications: Many prescription and over-the-counter medicines list diarrhoea as a side effect. Antibiotics are a major cause because they disrupt the balance of healthy gut bacteria alongside harmful bacteria. Non-steroidal anti-inflammatory drugs (NSAIDs) and certain antacids can also trigger loose stools.
• Stress and anxiety: Your gut and brain are intimately connected via the gut-brain axis. High levels of stress or anxiety can cause the gut to contract more rapidly, leading to sudden bouts of diarrhoea.

Long-term (chronic) causes:

If loose poo persists for more than four weeks, it could be a sign of an underlying digestive condition, such as:

• Irritable bowel syndrome (IBS): A common functional bowel condition where the gut is hypersensitive, often causing diarrhoea (IBS-D), constipation (IBS-C) or alternating bowel habits (IBS-M). Read our IBS information here.
• Inflammatory bowel disease (IBD): Conditions like Crohn’s disease or ulcerative colitis cause chronic inflammation along the digestive tract lining. Read our IBD information here.
• Coeliac disease: An autoimmune condition where eating gluten (a protein found in wheat, barley and rye) causes the body to attack the lining of the small intestine. Read our coeliac disease information here.
• Bile acid diarrhoea (BAD): A condition where excess bile acids enter the large intestine, stimulating the bowel to secrete excess water and speed up transit. Read our bile acid diarrhoea information here.
• Microscopic colitis: An inflammation of the large intestine that can only be diagnosed by looking at tissue samples under a microscope. It is a type of IBD, along with Crohn’s disease and ulcerative colitis.

How do I manage diarrhoea and look after myself?

When diarrhoea strikes, your main priority should be replacing lost fluids and resting. Here are some key self-care steps:

1. Stay hydrated

The biggest risk associated with diarrhoea, especially acute episodes, is dehydration. You lose vital fluids, salts and minerals (electrolytes) every time you pass a loose poo.

• Drink plenty of fluids throughout the day, taking small, frequent sips if you feel nauseous.
• Water is good, but squash, diluted fruit juice or clear broths help replenish electrolytes.
• Consider using oral rehydration therapy (ORT) sachets available from pharmacies, especially for vulnerable individuals like the elderly or young children.
• Avoid caffeine, alcohol, fizzy drinks and very sugary beverages, as these can irritate the gut and worsen diarrhoea.

2. Ease back into eating

You don’t need to stay away from food, but sticking to bland, gentle foods whilst your stomach settles can help.

• Eat small, light meals when you feel ready.
• Good choices include plain white rice, boiled potatoes, toast, crackers, bananas and plain soup.
• Avoid rich, spicy, fatty or fried foods, as well as high-fibre foods and dairy products until your bowel recovers.

3. Rest and practice good hygiene

Infections spread easily. If your diarrhoea is due to a stomach bug, stay at home, wash your hands thoroughly with soap and warm water after using the toilet and before preparing food. Also, avoid preparing meals for others until you have been symptom-free for at least 48 hours.

When should I see a doctor for diarrhoea?

While most short-term cases of diarrhoea clear up within a few days without medical treatment, it can sometimes be a sign of a serious underlying issue.

You should contact your GP if:

• Your diarrhoea lasts longer than seven days (or longer than two days in a young child).
• You notice a persistent, unexplained change in your bowel habits that lasts for more than three weeks.
• You have severe abdominal pain or cramping that doesn’t ease up.
• You are showing signs of severe dehydration (dark yellow urine, dizziness, confusion, dry mouth).
• You are losing weight unexpectedly.

Seek urgent medical attention or go to A&E if you experience red flag symptoms:

• Passing blood in your stool or passing dark, black, tarry stools.
• Persistent high fever (above 38c/100.4F)
• Uncontrollable vomiting that stops you from keeping fluids down.

Check your poo with the Guts UK Poo-Torial tool

Before you rush to dismiss a change in your bowel habits, it can literally save a life to take a closer look. Checking your poo is one of the easiest ways to monitor your digestive health.

To help you figure out what’s normal for you and what your body might be trying to tell you, check out our interactive Poo-Torial tool. It can tell you more about the colour, consistency and frequency of your poo, and when it might be time to contact your GP.

You’ve read the first in our ‘Get to grips with digestive symptoms’ series!

Digestive symptoms are incredibly common, but they are often seen as taboo to talk about. Over the coming months, we’ll be publishing symptom snapshot posts like this to help break down what is happening inside your body into digestible chunks (pun intended).

We’ll be taking a closer look at common causes of symptoms and sharing practical tips to manage your gut health.

Keep an eye out for upcoming symptom snapshots on:

• Constipation
• Bloating and distension
• Wind
• Indigestion
• Heartburn and acid reflux

Eager to learn more?

We have information about the digestive system and over 40 digestive conditions and symptoms, along with health and lifestyle, testing and monitoring, which can be found here. You can also follow us on social media by searching ‘gutscharityuk’ to learn more, keep up to date with the work we do and take part in vital awareness campaigns to help us spread the word that our guts deserve better. It’s time for the UK to get to grips with guts!

About Guts UK

Guts UK is the national charity for the digestive system. We are the only UK charity funding research into the whole digestive system.

People are suffering. People are dying. All because of a lack of knowledge about our guts. Guts UK exists to change that. 

You can find out more about what we do here.