What is diarrhoea?

Diarrhoea is when you have 3 or more loose or liquid stools (poos) in one day, or more frequently than normal. If you have diarrhoea, you will notice an increase in the volume, wateriness or frequency of your bowel movements.

Diarrhoea episodes are often caused by a stomach bug (gastroenteritis) and clear up on their own in a few days. However, there are many other causes of diarrhoea.

Most diarrhoea is mild, but it can also be severe enough to need to go to hospital.

This article covers diarrhoea in adults and children over 12 years. See diarrhoea in children for information about diarrhoea in young children.

What symptoms relate to diarrhoea?

As well as the loose and watery stools of diarrhoea, you may sometimes have other symptoms, including:

• nausea (feeling sick) and vomiting (being sick)
• fever
• headache
• bloating
• flatulence (excess gas)
• abdominal pain (tummy pain)
• loss of appetite

You may feel an urgent need to go to the toilet.

Dehydration can develop when you have diarrhoea, especially in children and older adults.

What causes diarrhoea?

Diarrhoea happens when not enough water is removed from your stool, or too much fluid is secreted into the stool, making it loose.

There are many different causes of diarrhoea. It can be caused by a short-term illness that clears up in a few days. If diarrhoea continues for weeks, it is likely to be a symptom of an ongoing problem or chronic condition.

Short-term causes of diarrhoea

Short-term diarrhoea is often due to infections, such as:

• food poisoning
• viral gastroenteritis — for example, caused by rotavirus or norovirus infection
• COVID-19 — nausea, diarrhoea and vomiting can all be symptoms of COVID-19
• waterborne parasites, such as cryptosporidium and giardia

Other causes of short-term diarrhoea can include:

• a change in diet
• certain food ingredients
• drinking too much alcohol
• stress

Long-term causes of diarrhoea

Diarrhoea can be caused by some long-term conditions, such as:

• inflammatory bowel disease (Crohn's disease and ulcerative colitis)
• irritable bowel syndrome
• food intolerances, such as lactose intolerance
• diverticular disease
• malabsorption syndromes — for example, after bowel surgery

People who are immunosuppressed or have weakened immune systems are more likely to develop ongoing diarrhoea after a bout of gastroenteritis. This includes people who have:

• cancer
• HIV/AIDS
• had an organ transplant

Medical treatments that can cause diarrhoea

Medical treatments that may cause diarrhoea as a side effect include:

• some medicines — for example, antibiotics
• laxatives, if too many are taken
• some treatments for cancer

How is the cause of diarrhoea diagnosed?

Your doctor will ask about your symptoms and take a medical history. They will also examine you.

If your diarrhoea goes away after a few days you may not find out the cause.

Sometimes, tests will be needed to diagnose the cause of your diarrhoea. These can include:

• blood tests
• stool tests
• endoscopy or colonoscopy (procedures where a thin tube with a camera on the end are used to view inside your stomach or bowel)

If you have ongoing diarrhoea, your doctor may refer you to a specialist for tests and to work out the underlying cause.

When should I see my doctor?

An isolated episode of diarrhoea will often clear up without any treatment and you won't need to see a doctor.

Seek medical advice if you have any of the following:

• ongoing diarrhoea
• blood and/or mucus in your stool (poo)
• a fever
• unexplained weight loss
• diarrhoea at night

When to seek urgent care

See you doctor immediately or go to the nearest hospital emergency department if you have:

• severe diarrhoea
• signs of dehydration (feeling tired, decreased urination, thirst and dry mouth)
• heavy rectal bleeding
• diarrhoea and severe abdominal pain

Diarrhoea can lead to dehydration and an electrolyte (salt) imbalance, making it dangerous — especially in very young or older people, who can get worse quickly.

How is diarrhoea treated?

Simple diarrhoea usually clears up by itself in healthy people. In many cases you will be able to manage your symptoms at home.

If your diarrhoea doesn't clear up on its own there are medicines and other treatments available.

Self-care at home

You should try to do the following:

• Rest at home.
• Stay off work or school until you have not had a loose bowel motion for 24 hours.
• Drink clear fluids or oral rehydration solution to replace lost fluids — take small sips if you feel sick.
• Avoid foods and drinks with artificial sweeteners — they can prolong the diarrhoea.
• Avoid alcohol and caffeine.
• Manage your diet until you get back to normal — eat bland foods, such as rice, pasta and crackers, and avoid fatty foods or those high in insoluble fibre.

You can buy oral rehydration solutions over the counter from your pharmacist or at the supermarket.

For older people and children, oral rehydration solutions are better than plain water. They contain the right concentration of salts to replace both fluids and electrolytes that your body needs.

Sports rehydration drinks are not recommended.

Medicines for diarrhoea

Check with your pharmacist or doctor if you are thinking of taking over-the-counter anti-diarrhoeal medicines. These are not suitable for use in all cases of diarrhoea. Do not take them if you have a fever or have blood in your stool.

Remember that diarrhoea can be your body's way of getting rid of an infection. Anti-diarrhoeal medicines should not be taken long term because they slow your gut and may prolong your illness.

Anti-diarrhoeal medicines should not be used to treat diarrhoea in children.

Other treatment options

Other treatments for diarrhoea will depend on the cause. They may include:

• Intravenous fluids — if you are not able to take in enough fluids by mouth you may need intravenous fluids via a drip.
• Antibiotics — if your stool sample shows that your diarrhoea is due to a bacterial infection, you may need antibiotics.
• Dietary changes — if you are experiencing diarrhoea for dietary reasons or due to irritable bowel syndrome, a dietitian should be able to help.

Can diarrhoea be prevented?

Gastroenteritis is the most common cause of diarrhoea. It is highly infectious, and mostly spread by contact with another person who has the illness. Gastroenteritis can also come from contaminated food.

To help to stop the spread of gastroenteritis:

• Wash your hands frequently using a good handwashing technique.
• Follow proper food-safety practices.
• Do not prepare food for others if you are unwell.
• Do not visit hospitals, aged care facilities or swimming pools when you have diarrhoea.
• Make sure your children are vaccinated against rotavirus.

If you are planning overseas travel, see your doctor about recommended vaccines.

What are the complications of diarrhoea?

Diarrhoea may cause dehydration because more fluids are lost than normal. It can also lead to an imbalance in electrolytes (salts and minerals your body needs to function properly.)

Ongoing diarrhoea can make it difficult for you to absorb nutrients from food and can lead to malnutrition.

Some people may develop temporary lactose intolerance after an episode of diarrhoea or gastroenteritis. See your doctor if the symptoms continue for more than a couple of weeks.

Resources and support

If you need advice on what to do if you have diarrhoea, call healthdirect on 1800 022 222 (known as NURSE-ON-CALL in Victoria) to speak with a registered nurse, 24 hours, 7 days a week.

Visit pregnancy birth and baby to learn about diarrhoea in babies and children.

For more information about chronic conditions associated with diarrhoea try these resources:

• The Gut Foundation
• GESA (Gastroenterological Society of Australia)