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Research · Supplements

D-mannose

The largest placebo-controlled trial, in 598 women with recurrent UTIs, found no difference from placebo over 6 months. Meta-analyses that include it find no significant reduction, with high heterogeneity. An earlier meta-analysis built on smaller trials reported fewer recurrences. Side effects in trials were few and mild, mostly diarrhea.

Add to Bio HackChecked 2026-11-09
Status
Dietary supplement in the US. Not approved by the FDA as a drug for any use.
Also called
mannose, d mannose, D-mannose powder, D-mannose tablets
Taken for
UTI, urinary tract infections, recurrent cystitis, bladder health, urinary tract health

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help0

No benefit shown in research yet.

Reported risks0

No risks sourced yet.

What people take it for, and what was found

Mixed results1

Moderate

Preventing recurrent urinary tract infections

Mixed results: the largest trial, of 598 women, and recent reviews found no reduction in UTIs, while a 2020 review of earlier studies found fewer.

The numbers and sources
Effect
In 598 women with recurrent UTI across 99 UK primary care centers, 2 g of D-mannose a day for 6 months did not change the share who sought care for a suspected UTI (51.0% against 55.7% on placebo, risk difference -5%, 95% CI -13% to 3%). No secondary outcome differed [1]. A 2025 meta-analysis of 4 RCTs (890 women) found no significant difference in recurrent UTI (RR 0.44, 95% CI 0.18 to 1.11, I² 90%) [2]. Another 2025 meta-analysis of 6 RCTs (1,167 participants) found no reduction against no treatment or antibiotics (RR 0.57, 95% CI 0.29 to 1.15) [3]. A 2022 Cochrane review of 7 RCTs (719 people) could not pool any studies and rated all evidence very low certainty [4]. A 2020 meta-analysis of 3 earlier studies reported a pooled RR of 0.23 against placebo (95% CI 0.14 to 0.37, 248 women) [5]. In one of those trials, 308 women were randomized after treatment for cystitis, and recurrence over 6 months was 14.6% on D-mannose, 20.4% on nitrofurantoin and 60.8% on no prophylaxis [6].
Population
Adult women with recurrent UTI [1][2][3][5][6]. Adults and children with cystitis or recurrent UTI [4].
Sources
[1], [2], [3], [4], [5], [6]
Caveats
Heterogeneity was high in the pooled analyses [2][3]. The no-prophylaxis arm in [6] had no placebo. The 2020 meta-analysis mixed one RCT, one crossover trial and one cohort study [5].

Doses studied

Trials used 2 g of D-mannose powder a day for 6 months [1][6]. Doses in the Cochrane review's trials ranged from 500 mg in combination products to 2 g, over 15 days to 6 months [4].

Risks

Checked, no increase found1

Limited

Side effects in trials

Limited evidence: adverse events were few and poorly reported, mainly diarrhea and vaginal burning, and none were serious.

The numbers and sources
Effect
Adverse events were few and poorly reported, and none were serious. The most common were diarrhea and vaginal burning [4]. In one D-mannose-only study, 8 of 103 participants had diarrhea [5]. Pooled adverse events did not differ from placebo or no treatment (RR 2.19, 95% CI 0.68 to 7.05, I² 79%) [2].
Population
Participants in the trials above [2][4][5].
Sources
[4], [5], [2]
Caveats
Reporting of harms was poor across trials [4]. The wide interval does not rule out a higher rate [2].

Claims tested and not found

  1. That daily D-mannose prevents recurrent UTIs in women in primary care. In 598 women, the share with a further medically attended UTI over 6 months did not differ from placebo [1].

Sources

  1. Hayward G, Mort S, Hay AD, et al. d-Mannose for Prevention of Recurrent Urinary Tract Infection Among Women: A Randomized Clinical Trial. JAMA Internal Medicine. 2024. https://doi.org/10.1001/jamainternmed.2024.0264
  2. Murali Krishna M, Joseph M, Pereira V, et al. D-Mannose for prevention of recurrent urinary tract infection in adult women: An updated systematic review and meta-analysis of randomized controlled trials. Journal of Infection Prevention. 2025. https://doi.org/10.1177/17571774251394869
  3. Vargas CEF, Mutarelli A, Menegardo LG, et al. Efficacy of D-mannose as prophylaxis of recurrent urinary tract infection: a systematic review and meta-analysis of randomized controlled trials. Brazilian Journal of Nephrology. 2025. https://doi.org/10.1590/2175-8239-jbn-2025-0169en
  4. Cooper TE, Teng C, Howell M, et al. D-mannose for preventing and treating urinary tract infections. Cochrane Database of Systematic Reviews. 2022. https://doi.org/10.1002/14651858.CD013608.pub2
  5. Lenger SM, Bradley MS, Thomas DA, et al. D-mannose vs other agents for recurrent urinary tract infection prevention in adult women: a systematic review and meta-analysis. American Journal of Obstetrics and Gynecology. 2020. https://doi.org/10.1016/j.ajog.2020.05.048
  6. Kranjčec B, Papeš D, Altarac S. D-mannose powder for prophylaxis of recurrent urinary tract infections in women: a randomized clinical trial. World Journal of Urology. 2014. https://doi.org/10.1007/s00345-013-1091-6

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