What should you know about watery diarrhoea?

A short episode may follow gastroenteritis or food poisoning, especially when cramps, nausea, vomiting, or fever occur. Giardiasis is another infection that can cause prolonged watery stools. Recurrent symptoms may occur with food intolerance, irritable bowel syndrome, coeliac disease, Crohn's disease, or an overactive thyroid. The stool symptom alone cannot identify the cause.

Dehydration may cause thirst, a dry mouth, dark urine, reduced urination, tiredness, dizziness, or faintness. Young children, older adults, and people with significant medical conditions can become unwell sooner and may need earlier advice.

Take frequent small sips of water or an oral rehydration drink. Continue eating light foods when able, and avoid alcohol. Wash hands carefully after using the toilet and before preparing food. Do not prepare food for others while unwell, and clean bathroom surfaces to reduce spread.

Avoid anti-diarrhoeal medicine if you have blood in the stool, a high fever, or severe abdominal pain unless a clinician advises it. Do not start antibiotics without assessment; many episodes improve without them, while some require a specific treatment.

Seek urgent care for severe dehydration, fainting, confusion, severe or localised abdominal pain, blood or black stool, or repeated vomiting that prevents drinking. Arrange medical advice when diarrhoea is persistent, keeps returning, follows recent travel or antibiotics, or affects a person who is pregnant, frail, or medically vulnerable.

Tell the clinician when symptoms began, how often stools occur, whether there is fever, pain, blood, vomiting, travel, sick contacts, or a recent medicine change. Ask whether you need stool testing, blood tests, rehydration treatment, or review for an underlying digestive or thyroid condition.