Bad diarrhoea: what should you know?

Sudden diarrhoea commonly follows gastroenteritis or food poisoning, but travel-related infection such as giardiasis is another possibility. Ongoing or recurring loose stools can occur with food intolerance, irritable bowel syndrome, coeliac disease, Crohn’s disease, or an overactive thyroid. The symptom alone cannot identify its cause.

Record when it began, how often you pass stool, its appearance, recent foods, travel, medicines, sick contacts, and associated vomiting or pain. This information helps a clinician choose the right assessment.

Take frequent small sips of water or an oral rehydration drink, especially after each loose stool. Eat small portions when able, choosing familiar foods, and avoid alcohol and foods that clearly worsen symptoms. Wash hands carefully and avoid preparing food for others while unwell. Ask a pharmacist before using an anti-diarrhoeal medicine, particularly for a child or when there is fever or blood.

Get urgent help for fainting, confusion, very little urine, inability to keep fluids down, severe or worsening abdominal pain, black stools, or visible blood. Prompt assessment is needed for a vulnerable adult, a young child, persistent vomiting, or diarrhoea that is not settling. Seek advice sooner after recent antibiotics, travel, or hospital care.

Could this be an infection, food reaction, medicine effect, or bowel condition? Do I need stool tests or blood tests? Which rehydration drink is suitable for me? When can I safely return to work, school, or food preparation?