What should you know about green watery diarrhoea?

Bile is naturally green and normally changes colour as it travels through the digestive system. When stool moves quickly, there is less time for that change, so diarrhoea may look green and remain watery. Green foods, food colouring, antibiotics and a sudden dietary change can also alter stool colour.

A short episode may occur with gastroenteritis or food poisoning. Ongoing or recurring diarrhoea can also occur with food intolerance, coeliac disease, irritable bowel syndrome, Crohn's disease, giardiasis or an overactive thyroid. The colour alone cannot identify the cause.

Take frequent small sips of water or an oral rehydration drink. Broth and other gentle fluids may help, while alcohol can worsen fluid loss. Eat when able; plain rice, bread, bananas, potatoes and soup may be easier to tolerate. Avoid rich, greasy foods and pause foods that clearly trigger symptoms.

Wash your hands carefully after using the toilet and before preparing food. Do not prepare meals for other people while you have diarrhoea. A pharmacist or clinician can advise whether an anti-diarrhoeal medicine is suitable; do not use one to delay assessment when you have blood in the stool or a fever.

Seek urgent medical help for severe or worsening tummy pain, faintness, confusion, very little urine, a dry mouth with intense thirst, blood or black stool, or repeated vomiting that prevents drinking. A high fever or marked weakness also needs prompt assessment.

Arrange medical advice if diarrhoea continues, keeps returning, follows recent antibiotics or travel, or affects a young child, older adult, pregnant person or someone with a long-term illness. A clinician may ask about foods, medicines, contacts, travel and hydration, and may arrange stool testing when appropriate.

Ask: What cause fits my timing and other symptoms? How should I replace fluids? Should I pause any medicine or food supplement? Do I need stool tests? What changes should prompt urgent help? Bring a list of medicines, recent travel, unusual foods and the number of loose stools you have had.