D-Mannose for UTIs: Early Trials Looked Promising, but the Largest Placebo Trial Found No Benefit
D-mannose is a simple sugar sold to stop repeat urinary tract infections. An early open trial looked strong, but a 2024 placebo-controlled trial in nearly 600 women found no meaningful reduction, and pooled analyses disagree. Here is what each trial found, who paid for it, and who should be careful.
By Kymata Health Editorial Published Last checked
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Quick pick
From a partner brand · paid link
NOW Foods, D-Mannose Powder, 6 oz
from HerbsPro
Label: 1 level teaspoon (about 2 g): 2 g D-mannose, the amount used in the trials.
Best for trying one bottle: $30.70 one-time (checked Oct 13, 2026).
Key takeaways
From 4 sources- In the largest placebo-controlled trial, 598 UK women with recurrent UTIs took 2 g of D-mannose or placebo daily for 6 months; 51.0% on D-mannose and 55.7% on placebo had another suspected UTI, a difference that was not statistically significant1.
- An earlier Croatian trial in 308 women found far fewer recurrences on D-mannose than on no treatment (14.6% vs 60.8%), but it had no placebo and was not blinded2.
- A 2025 meta-analysis of 4 randomized trials (890 women) found no significant reduction in recurrent UTIs, with very inconsistent results between trials4.
- Side effects in the trials were mild; diarrhea was the main complaint reported in an early review3.
- D-mannose is not a substitute for checking a current infection, and the authors of the largest trial concluded it should not be recommended for prevention in women like those they studied1.
What this article covers
1 evidence profileThe evidence, graded
Pulled from the trial tables in our evidence profiles. Grades follow our evidence-grading policy.
Graded findings
4 rows- ∅No effectRecurrent UTI in women in primary careNo effect A clinically suspected UTI occurred in 51.0% vs 55.7% (risk difference −5%, 95% CI −13% to 3%; P = 0.26); no secondary outcome differed.D-mannose · RCT · n=583 · 2024 · PMID 38587819
- CGrade CRecurrent UTI vs nitrofurantoin and no prophylaxisImproved Recurrence 14.6% with D-mannose, 20.4% with nitrofurantoin and 60.8% with no prophylaxis (RR 0.239 vs no prophylaxis); side effects were mild and less frequent than with nitrofurantoin.D-mannose · RCT · n=308 · 2014 · PMID 23633128
- CGrade CRecurrent UTI (pooled RCTs)Mixed Recurrent UTI RR 0.44 (95% CI 0.18–1.11; P = 0.082; I² 90%); adverse events did not differ significantly.D-mannose · Meta-analysis · n=890 · 2025 · PMID 41195062
- DGrade DRecurrent UTI vs placebo or antibiotics (early studies)Improved Pooled RR vs placebo 0.23 (95% CI 0.14–0.37) from small early studies; vs preventive antibiotics RR 0.39 (95% CI 0.12–1.25, not significant).D-mannose · Systematic review · n=248 · 2020 · PMID 32497610
Why people take D-mannose
D-mannose is a simple sugar sold as a powder or capsule for urinary health. Whatever the proposed mechanism, the human trials below are the real test of whether it works.
Recurrent UTIs are common: a 2025 review notes that about half or more of adult women have at least one UTI in their lifetime, and around a fifth of them have another within a year4.
The largest trial: no meaningful benefit
The 2024 UK trial, run across 99 UK primary care practices, randomized 598 women aged 18 to 93 (average 58) who had had at least 2 UTIs in 6 months or 3 in a year1. They took 2 g of D-mannose powder or a matched placebo powder daily for 6 months1.
Another clinically suspected UTI occurred in 150 of 294 women on D-mannose (51.0%) and 161 of 289 on placebo (55.7%), a risk difference of 5 percentage points with a confidence interval running from 13 points better to 3 points worse (P = 0.26)1. Symptom length, antibiotic use, time to the next UTI and hospital admissions did not differ either1.
The trial was funded by the UK National Institute for Health and Care Research, which had no role in its design, analysis or reporting, and the authors reported no conflicts of interest1. They concluded that D-mannose should not be recommended for prophylaxis in this group1.
Why earlier studies looked better
In a Croatian trial, 308 women with recurrent UTIs first received antibiotics for a bladder infection and were then assigned to 2 g of D-mannose in 200 mL of water daily, 50 mg of the antibiotic nitrofurantoin daily, or nothing, for 6 months2. Recurrences occurred in 14.6% on D-mannose, 20.4% on nitrofurantoin and 60.8% with no prevention2. There was no placebo group and no blinding, which can exaggerate benefits, and its PubMed record does not state who funded it2.
A 2020 meta-analysis pooled 3 studies of varied design and found a lower recurrence risk with D-mannose than placebo (relative risk 0.23), based on about 125 women per group3. The authors cautioned that the studies were few, small and of mixed quality, and the review was supported by US National Institutes of Health grants with no conflicts reported3.
Once the large placebo-controlled trial was included, a 2025 meta-analysis of 4 randomized trials (890 women) found a relative risk of 0.44 that was not statistically significant (P = 0.082), with very high inconsistency between trials4. Its authors declared no conflicts of interest and said more placebo-controlled trials are needed4.
How it compares with other options
For the other supplement most often tried for repeat UTIs, see our explainer on cranberry for UTIs, and for antibiotic side effects, probiotics with antibiotics. The D-mannose page grades each D-mannose finding.
Who should be careful
Check with a doctor or pharmacist before relying on D-mannose if any of these apply:
- Symptoms of a current UTI (burning, urgency, fever, back pain or blood in the urine): these need assessment, and in the largest trial D-mannose did not reduce further infections1.
- Taking a preventive antibiotic: the only trial comparing D-mannose with nitrofurantoin was small and unblinded2, so switching should be a decision made with the prescriber.
- Other regular medicines: we found no published drug-interaction studies for D-mannose, which means the risk is unknown rather than shown to be zero, so tell your pharmacist you take it.
- Sensitive digestion: diarrhea was reported in 8 of 103 women taking D-mannose in one early study3.
- Pregnancy, men and children: the trials described here enrolled adult women124 and do not report separate results for pregnancy, so these groups need a clinician's advice.
Quick answers
Common questions
4 answersHow much D-mannose was used in the trials?
Is D-mannose as good as antibiotics for stopping repeat UTIs?
Can D-mannose clear an active UTI?
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Where to buy D-mannose
Products from brands we partner with that contain D-mannose. Check the amount per serving against the doses studied, and the label for other ingredients.
D-mannose products from partner brands
1 product Paid links · we earn a commission- Quick pickHerbsProNOW Foods, D-Mannose Powder, 6 oz
1 level teaspoon (about 2 g): 2 g D-mannose, the amount used in the trials
$30.70one-timeChecked Oct 13, 2026
References
4 sources. Numbers in the text link here.
Sources cited in this article
4 sources- 1d-Mannose for Prevention of Recurrent Urinary Tract Infection Among Women: A Randomized Clinical TrialJAMA Intern Med, 2024 · PMID 38587819
- 2D-mannose powder for prophylaxis of recurrent urinary tract infections in women: a randomized clinical trialWorld J Urol, 2014 · PMID 23633128
- 3D-mannose vs other agents for recurrent urinary tract infection prevention in adult women: a systematic review and meta-analysisAm J Obstet Gynecol, 2020 · PMID 32497610
- 4D-Mannose for prevention of recurrent urinary tract infection in adult women: An updated systematic review and meta-analysis of randomized controlled trialsJ Infect Prev, 2025 · PMID 41195062
D-mannose and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. Product links on this page are paid partner links.