Diarrhoea

Diarrhoea is something most people experience at some point in their lives. For many, it is a brief and uncomfortable inconvenience that passes within a day or two. For others, particularly when symptoms are persistent or severe, diarrhoea can signal an underlying condition that warrants proper investigation. Understanding the difference is important for knowing when to manage symptoms at home and when to seek medical advice.

What is Diarrhoea?

Diarrhoea is defined as passing three or more loose or watery stools in a single day, or more frequently than is usual for you. You may also notice an increase in the volume or wateriness of your bowel motions, along with an urgent need to reach the toilet.

Under normal circumstances, the large intestine absorbs water from digested food waste before it is passed from the body as formed faeces. Diarrhoea occurs when this process is disrupted, either because not enough water is removed from the stool, or because excess fluid is secreted into the bowel, leaving stools loose and watery.

Diarrhoea is broadly classified into two types. Acute diarrhoea comes on suddenly and typically resolves within a few days. Chronic diarrhoea persists for four weeks or more and is more likely to reflect an ongoing health condition requiring specialist assessment.

Symptoms associated with Diarrhoea

The primary symptom is the frequent passing of loose or liquid stools, often accompanied by a sudden and strong urge to go to the toilet. Additional symptoms that may occur alongside diarrhoea include abdominal pain or cramping, nausea, vomiting, fever, headache, bloating, excess gas, and a loss of appetite.

Dehydration is a common and important complication of diarrhoea. It develops when the body loses more fluid than it takes in, and it can progress quickly, particularly in young children, older adults, and people with pre-existing health conditions. Signs of dehydration include fatigue, reduced urination, thirst, and a dry mouth.

When to seek urgent medical attention

Most episodes of acute diarrhoea in otherwise healthy adults will resolve without medical treatment. However, you should seek prompt medical attention if you experience blood or mucus in your stool, heavy rectal bleeding, severe abdominal pain, diarrhoea at night, signs of dehydration, a fever, or unexplained weight loss. Ongoing diarrhoea that does not improve on its own also warrants review by a doctor.

If you have a serious pre-existing condition such as kidney disease or heart failure, even a single day of diarrhoea can carry significant risks, and it is advisable to see your doctor promptly rather than waiting. In an emergency, always call triple zero (000) or go directly to your nearest hospital emergency department.

What causes acute diarrhoea?

The most common cause of acute diarrhoea is a gastrointestinal infection, such as gastroenteritis or food poisoning. These infections are most often caused by viruses, including norovirus and rotavirus, though bacteria such as Salmonella, Campylobacter, and Escherichia coli (E. coli), as well as parasites such as Giardia and Cryptosporidium, are also responsible in a significant number of cases.

Infection is typically spread through contact with an affected person, contaminated food or water, or contact with contaminated surfaces. Other causes of short-term diarrhoea include a sudden change in diet, certain food ingredients, excessive alcohol intake, stress, and some medications, particularly antibiotics. COVID-19 can also cause gastrointestinal symptoms including diarrhoea, nausea, and vomiting.

What causes Chronic Diarrhoea?

When diarrhoea persists for four weeks or longer, it is more likely to be related to an ongoing health condition. Common causes of chronic diarrhoea include inflammatory bowel disease (including Crohn’s disease and ulcerative colitis), irritable bowel syndrome, food intolerances such as lactose intolerance, coeliac disease, and diverticular disease. Malabsorption syndromes that develop after bowel surgery can also lead to persistent loose stools.

Certain medications can contribute to chronic diarrhoea as a side effect, including some drugs used to manage diabetes, high blood pressure, and arthritis, as well as laxatives when taken in excess, some immunosuppressive agents, and certain treatments used in the management of cancer. Cancer, including bowel cancer, is among the less common but important causes of persistent diarrhoea that should be investigated.

People with weakened immune systems, including those living with HIV or AIDS, those who have undergone organ transplantation, or those taking immunosuppressive medications, are at greater risk of developing ongoing diarrhoea, including following a bout of gastroenteritis.

How is the cause of diarrhoea diagnosed?

For most short-term episodes, diarrhoea resolves before a cause is formally identified. When symptoms are persistent, severe, or concerning, your doctor will take a thorough medical history and conduct a physical examination. Depending on the clinical picture, investigations may include blood tests, stool analysis, and, where an underlying bowel condition is suspected, endoscopy or colonoscopy. A colonoscopy involves a slender flexible instrument being passed through the bowel to allow direct assessment of the bowel lining.

If your diarrhoea is ongoing and the cause is not identified by your general practitioner, referral to a gastroenterologist for specialist assessment and investigation is appropriate. Identifying the underlying cause is essential for guiding the right treatment.

Managing Diarrhoea at home

Simple acute diarrhoea in otherwise healthy adults will often resolve with supportive care at home. Staying well hydrated is the most important priority. Oral rehydration solutions, available from pharmacies and supermarkets, are recommended for older adults and children as they contain the right balance of fluid and electrolytes. Plain water is less effective at replacing the salts and minerals lost during diarrhoea. Sports drinks are not recommended as a substitute for oral rehydration solutions.

While you recover, it is advisable to rest at home and stay away from work or school until you have not had a loose bowel motion for at least 24 hours. Eat bland foods such as rice, pasta, and crackers. Avoid fatty foods, those high in insoluble fibre, artificial sweeteners, alcohol, and caffeine, as these can prolong symptoms.

Before taking over-the-counter anti-diarrhoeal medicines, speak with your pharmacist or doctor. These medications are not suitable in all situations. They should not be taken if you have a fever or blood in your stools, and they are not appropriate for use in children. Anti-diarrhoeal medicines slow gut motility and can prolong illness, particularly when diarrhoea is caused by infection.

Medical treatment for diarrhoea

When diarrhoea requires medical treatment, the approach depends on the underlying cause. If a bacterial infection is identified through stool testing, antibiotic therapy may be prescribed. In cases where adequate fluid intake cannot be maintained by mouth, intravenous fluid replacement may be necessary.

Where diarrhoea is related to dietary factors or conditions such as irritable bowel syndrome, dietary modification plays an important role in management. Our gastroenterology team works alongside an accredited practising dietitian, who is accessible to patients without the need for a specialist referral. This allows for tailored nutritional guidance to support your recovery and ongoing gut health.

For diarrhoea associated with a chronic condition such as inflammatory bowel disease, a longer-term management plan will be developed in partnership with your gastroenterologist, taking into account your individual circumstances, symptom patterns, and overall health.

Preventing the spread of infectious diarrhoea

Gastroenteritis is the most common cause of infectious diarrhoea and is highly contagious. It spreads primarily through direct contact with an infected person, through contaminated food or water, and occasionally via airborne particles generated during vomiting. Reducing your risk of spreading infection involves thorough and frequent handwashing using good technique, following safe food handling practices, and not preparing food for others while you are unwell.

If you have diarrhoea, it is strongly recommended that you avoid visiting hospitals, aged care facilities, and public swimming pools until you have fully recovered. Vaccination against rotavirus is recommended for infants and can significantly reduce the risk of severe gastroenteritis in young children. If you are travelling overseas, speak with your doctor beforehand about recommended vaccinations for your destination.

Complications of Diarrhoea

The most significant complication of diarrhoea is dehydration, which occurs when fluid losses exceed what the body can replace through normal intake. Electrolyte imbalance, a disruption in the levels of salts and minerals the body needs to function properly, can also occur alongside dehydration and carries its own health risks.

Prolonged diarrhoea can interfere with the absorption of nutrients from food, potentially leading to nutritional deficiencies. Some people develop a temporary intolerance to lactose following an episode of diarrhoea or gastroenteritis. If this persists for more than a couple of weeks, it is worth discussing with your doctor.

When to see a gastroenterologist

A single isolated episode of diarrhoea that resolves quickly in a healthy adult will rarely require specialist input. However, diarrhoea that is persistent, recurrent, associated with blood in the stool, accompanied by unexplained weight loss, or that occurs at night warrants thorough investigation. These features can be associated with inflammatory bowel disease, coeliac disease, bowel cancer, and other conditions that are best assessed and managed by a specialist.

Our gastroenterology specialists in Brisbane offer comprehensive assessment for patients experiencing persistent or concerning gastrointestinal symptoms. We provide access to the full range of diagnostic investigations, including colonoscopy, to help identify the cause of your symptoms and guide appropriate management.

If you are experiencing ongoing diarrhoea symptoms and are looking for answers, we encourage you to speak with your GP about a referral.

If you have received a referral to see one of our doctors, you can request an appointment online, or contact our rooms directly on (07) 3321 1500.

This information has been sourced and adapted from education resources developed by

• Health Direct Australia (Health Direct)
• Better Health Channel Victoria (Better Health Channel)