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Diarrhoea: Causes, Home Care, and When to See a GP

Bristol Stool Types 6-7 - Updated April 2026

What Is Diarrhoea?

The NHS defines diarrhoea as passing loose or watery stools more than three times per day. On the Bristol Stool Chart, types 6 and 7 represent diarrhoea: mushy with ragged edges (type 6) or entirely liquid with no solid pieces (type 7). Both indicate faster-than-normal colonic transit, meaning stool has not had enough time for adequate water reabsorption.

Acute Diarrhoea

Lasts fewer than 14 days. Usually caused by infection (norovirus, Salmonella, Campylobacter, food poisoning) or medication side effects. Generally self-limiting with rehydration.

Chronic Diarrhoea

Lasts more than 4 weeks. Requires investigation. Causes include IBS-D, IBD, coeliac disease, bile acid diarrhoea, microscopic colitis, and others.

Acute Causes of Diarrhoea

Norovirus (winter vomiting bug)
Most common UK cause. Extremely contagious. Self-limiting in 2-3 days. Strict handwashing, avoid food preparation for 48h after recovery.
Campylobacter
UK's most common bacterial food poisoning. Undercooked poultry. Can be severe, may require antibiotics.
Salmonella
Eggs, poultry, reptiles. Self-limiting in 4-7 days for most. GP if severe or persistent.
E. coli (STEC, including O157)
Undercooked beef, unpasteurised milk, contaminated water. STEC strains can cause haemolytic uraemic syndrome - seek urgent care.
Post-antibiotic diarrhoea
Antibiotics disrupt gut microbiome. Usually mild and self-resolving; if severe or associated with fever, check for C. difficile.
Traveller's diarrhoea
Contaminated water or food abroad. Usually E. coli strains. ORS + short-course azithromycin if severe.
Food intolerance (acute exposure)
Large lactose or fructose load, or accidental gluten exposure in coeliac disease.

Chronic Causes of Diarrhoea

IBS-D
The most common chronic diarrhoea cause in otherwise healthy adults. No structural abnormality. Rome IV diagnosis requires 6 months history, >25% stools types 6-7.
Bile acid diarrhoea (BAD)
Affects ~1% of UK population, up to 35% of IBS-D patients. Often missed. Common after cholecystectomy. Treatable with colestyramine or colesevelam.
Coeliac disease
Autoimmune gluten response causing villous atrophy. Prevalence ~1% UK. Blood test (tTG-IgA) then endoscopic biopsy. Strict lifelong gluten-free diet.
Inflammatory bowel disease (Crohn's/UC)
Structural inflammation. Usually has blood or mucus. Urgent investigation required.
Microscopic colitis
Collagenous or lymphocytic colitis. Watery diarrhoea (type 7), often in older women. Normal colonoscopy; biopsy required for diagnosis.
Metformin
Up to 20-30% of metformin users experience diarrhoea. Slow titration and extended-release formulation reduces this.

Oral Rehydration: The Essential First Step

Rehydration is the most important treatment for diarrhoea. Plain water does not replace the electrolytes (sodium, potassium, chloride) lost through watery stool. Oral rehydration salts (ORS) contain the right glucose-to-electrolyte ratio to maximise intestinal water absorption via the glucose-sodium co-transporter.

Home ORS Recipe (WHO/UNICEF formula)

1 litre of clean water (boiled and cooled if unsure of purity)
6 level teaspoons of white sugar (sucrose)
Half a level teaspoon of salt (sodium chloride)

Or use pharmacy ORS sachets: Dioralyte, Electrolytes Plus, etc. - more accurate and more convenient.

Drink 200-400ml after each loose stool. Sip frequently rather than drinking large volumes at once, especially if nausea is present. Avoid sports drinks, fruit juice, and fizzy drinks as rehydration fluids.

Probiotics for Diarrhoea: What the Evidence Shows

Saccharomyces boulardii CNCM I-745 (available as Florastor) has the strongest clinical evidence for diarrhoea of any probiotic strain. It is particularly effective for post-antibiotic diarrhoea (including C. difficile prevention), traveller's diarrhoea, and acute infectious diarrhoea. A Cochrane meta-analysis found it significantly reduced the duration of acute diarrhoea in adults and children.

For IBS-D specifically, Bifidobacterium infantis 35624 (Alflorex) has UK-based clinical trial data and is referenced in NICE guidance. See our partner site probioticvsprebiotic.com for a full evidence comparison by strain.

When to See a GP or Call 111

See a GP if:

-Diarrhoea lasting more than 7 days
-Blood or pus in stool
-Fever above 38.5°C
-Recent foreign travel
-Recent antibiotic course (C. diff risk)
-Significant weight loss

Call 111 or 999 if:

!Cannot keep any fluids down
!Signs of severe dehydration (confusion, no urine for 8h)
!High fever (above 39°C) with diarrhoea
!Blood with watery diarrhoea - 999
!Infant or elderly person deteriorating quickly

Type 6 (mushy)Type 7 (watery)IBS-D guide IBD flare signs Red flags

Updated April 2026. Sources: NHS UK. NICE CG84. Cochrane S. boulardii meta-analysis. Rome IV criteria.