Causes of Diarrhoea
A practical, safety-focused guide for patients and families
Co-branded with Anonamed — privacy-first emergency medical record
What this site is for
Diarrhoea is extremely common. Most episodes are short-lived and harmless, but a small number can lead to serious dehydration, infection, or sepsis, especially in vulnerable people.
This site is designed to help you:
- manage diarrhoea safely at home when appropriate
- recognise red flags early
- avoid unnecessary tests and antibiotics
- not miss serious disease
It is written by a gastroenterology perspective and follows modern clinical practice.
DiarrheaCauses.com: a 60-second safety check
Before reading anything else, answer these four questions:
1. Can fluids stay down?
- Are you able to keep fluids down without persistent vomiting?
- Is urine output reduced, dark, or absent?
If fluids cannot stay down, dehydration risk is high.
2. Is there blood, black stool, or high fever?
- Fresh red blood or dark/black stool
- Fever above 38.5°C (101.5°F)
- Severe or worsening abdominal pain
These are not normal for simple gastroenteritis.
3. How long has it lasted?
- 0–14 days → usually acute diarrhoea
- 14–28 days → persistent diarrhoea
- ≥4 weeks → chronic diarrhoea (needs structured evaluation)
Duration matters more than stool frequency alone.
4. Are you in a higher-risk group?
Lower thresholds for assessment apply if you are:
- an infant or young child
- over 65 years old
- pregnant
- immunosuppressed (biologics, steroids, chemotherapy, transplant)
- without a spleen (asplenia)
- living with significant heart, kidney, or liver disease
The single most important principle
Dehydration causes more harm than diarrhoea itself.
Early oral rehydration prevents most complications. Antibiotics rarely help and often make outcomes worse when used incorrectly.
Common patterns — and what they usually mean
| Pattern | Often suggests | Safer next step |
|---|---|---|
| Watery diarrhoea + vomiting, others ill | Viral gastroenteritis | Oral Rehydration Solution (ORS), antiemetic if needed |
| Sudden onset after food, intense vomiting | Toxin-mediated food poisoning | Fluids, no antibiotics |
| Fever and/or blood in stool | Invasive bacterial infection or colitis | Medical review, stool testing |
| Watery diarrhoea after recent antibiotics or hospital stay | C. diff | Targeted stool testing |
| Greasy, pale, floating stools + weight loss | Malabsorption / pancreatic insufficiency | Specialist evaluation |
| Urgency shortly after meals | Bile acids, dumping, rapid transit | Post-prandial pathway |
What not to do
- Do not start antibiotics “just in case”
- Do not use loperamide if there is fever or blood
- Do not ignore dehydration because stool frequency seems mild
- Do not delay care if symptoms worsen rapidly
Where to go next on this site
- Timeline: What to expect — day-by-day guidance to reduce anxiety
- When to seek medical attention — clear red flags
- Rehydration & symptom relief — ORS, vomiting strategies, safe medication use
- Testing & investigations — stool PCR, blood tests, imaging, colonoscopy cautions
- Antibiotics — when they help, when they harm
- Traveller’s diarrhoea — prevention and hospital thresholds
- Chronic diarrhoea — structured causes and investigations
A note on emergencies and privacy (Anonamed)
If diarrhoea becomes severe — particularly while travelling — clinicians need to know:
- drug allergies (especially anaphylaxis)
- immunosuppression
- prior C. diff
- major abdominal surgery
Carrying this information securely and privately can be life-saving. This site is co-branded with Anonamed for that reason.
Important disclaimer: This site provides general medical information, not personal medical advice. If you are deteriorating, dehydrated, confused, or severely unwell, seek urgent medical care.