Supplement
D-mannose
D-mannose is a simple sugar sold as a powder or capsules, mainly to prevent repeat bladder infections; it is thought to stop E. coli bacteria from attaching to the bladder lining. In the largest placebo-controlled trial, women with recurrent infections who took it daily for 6 months had about as many further infections as women on placebo. Earlier trials without a placebo looked positive, but pooled analyses found no significant benefit and a Cochrane review rated the evidence very low certainty. Reported side effects are uncommon, mostly diarrhoea.
Sources: PMID 38587819; PMID 41942398; PMID 36041061
- Updated
- How we grade
- Best evidence
- Not graded
What d-mannose is good for
How we grade →We are re-checking D-mannose’s graded outcomes against their studies. Until they are re-checked we don’t summarise them here; every outcome is in the evidence below.
Is d-mannose safe?
Safety note. Talk to a doctor or pharmacist before you start d-mannose if you take prescription medicines, are pregnant or breastfeeding, or have a long-term health condition. Supplements can interact with medicines.
Evidence by condition
- Strong
- Moderate
- Limited
- Very limited
CUrinary Tract Infection
Recurrence Risk1 outcome · 6 studies
Urinary Tract Infection: all the evidence on its own page
| Grade | Outcome | Effect | Size and studies |
|---|---|---|---|
| C | Recurrence RiskMixed effectStudied as: Adult women with repeated urinary tract infections took 2 to 3 g of D-mannose powder by mouth daily for about 6 months, compared with placebo or no treatment. The large placebo-controlled trial found no benefit, while smaller trials without placebo found fewer infections. The Cochrane review 36041061 rated the evidence very low certainty.Studies that measured recurrence risk (6 studies)
| 6 studiesReviewed |