Probiotics: What to Do, in Order
Probiotics: what is worth doing, what is worth avoiding, and when to stop and see a doctor.
Live microorganisms taken with the intention of conferring a health benefit. Effects are strain-specific and condition-specific, which makes most general claims about "probiotics" close to meaningless.
Key takeaways
- Effects: strain-specific; products are not interchangeable
- Best evidence: antibiotic-associated diarrhoea and some IBS symptoms
- Most useful single change: Choose a product studied for your specific condition, not a generic one.
- Commonest mistake: Assuming all probiotics do the same thing.
- See a doctor if any of the signs under "When to speak to a doctor" below apply to you.
Do
- Choose a product studied for your specific condition, not a generic one
- Give it at least four weeks before judging
- Increase dietary fibre diversity, which has better evidence than any capsule
- Stop if symptoms worsen
Do not
- Assuming all probiotics do the same thing
- Live products if you are significantly immunosuppressed, without advice
- Expecting a supplement to substitute for dietary change
The numbers behind the list
The list is built from the numbers below, which come from the bodies cited at the end.
| Measure | Figure |
|---|---|
| Effects | strain-specific; products are not interchangeable |
| Best evidence | antibiotic-associated diarrhoea and some IBS symptoms |
| Regulation | sold as food supplements, not medicines |
| Trial period commonly suggested | at least 4 weeks |
| Fermented foods | a food-based alternative, though not standardised |
If you change one thing
Choose a product studied for your specific condition, not a generic one. If you only change one thing, make it that.
Where to go next
- Answers to the Common Questions on Probiotics
- Probiotics: Just the Figures
- Probiotics — the reference entry
- The Evidence on Liver Health, Without the Hype
- Irritable Bowel Syndrome: What Published Guidance Supports
When to speak to a doctor
Check with your clinical team before taking live probiotic products if you are immunosuppressed, have a central venous line, or are critically unwell — rare serious infections have been reported. See a GP for persistent change in bowel habit, blood in the stool or unexplained weight loss rather than self-treating.
Where this comes from
- British Dietetic Association — probiotics
- NHS — Probiotics
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarised or generalised beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.
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