Diarrhoea in Adults: Causes and When to Worry

Diarrhoea usually clears up within two to four days without treatment. The biggest risk is dehydration, especially for older adults and people with long-term conditions.

Imagine a sudden bout of diarrhoea after a family meal out. You feel weak and dizzy by evening. Sipping oral rehydration solution steadily overnight keeps you out of hospital, and by day three you’re eating normally again.

Common causes

• Short-term: viral gastroenteritis, food poisoning, traveller’s diarrhoea, antibiotics, alcohol
• Longer-term: irritable bowel syndrome, coeliac disease, lactose intolerance, inflammatory bowel disease, overactive thyroid, some medicines

Caring for yourself at home

• Drink plenty of fluids; take small sips often if you’re also vomiting
• Use oral rehydration solution if you’re dehydrated or vulnerable
• Eat when you feel able; plain foods are easiest
• Wash hands thoroughly with soap and water
• Stay off work or school until 48 hours after the last episode, especially if you work with food or patients

Anti-diarrhoea medicines like loperamide can help some adults, but avoid them if you have a high fever or blood in your stool. Ask a pharmacist if you take other medicines, as some (such as diabetes or blood pressure tablets) may need pausing during dehydration.

But when should I worry?

See a doctor urgently for blood in your stool, black stools, severe tummy pain, a high fever, signs of dehydration (very little urine, dizziness, confusion), or diarrhoea after recent hospital treatment or antibiotics. Also get checked if diarrhoea lasts more than a week, keeps coming back, or comes with weight loss.

Sources: World Health Organization (Diarrhoeal disease), NHS (Diarrhoea and vomiting), World Gastroenterology Organisation, US CDC.