Can D-Mannose prevent recurrent UTI? The MERIT (D-Mannose to prEvent Recurrent Urine InfecTions) randomised double blind placebo controlled trial

Talk Code: 
Gail Hayward
Sam Mort, Nicola Williams, Jared Robinson, Julie Allen, Nicola Maeder, Rebecca Edeson, Nicholas Thomas, Alastair Hay, Michael Moore, Christopher Butler
Author institutions: 
University of Oxford, University of Brstol, University of Southampton


Recurrent Urinary Tract Infection (UTI) is a particular challenge for primary care. It causes significant morbidity and reduced quality of life for women and results in repeated antibiotic usage and multi-drug resistance. Prophylaxis with antibiotics is only effective while taken, and the evidence for non-antibiotic prophylactic options is limited.D-Mannose is a sugar which is argued to prevent binding of the E coli type 1 Pili to urothelial cells. It is an expensive food supplement not available on prescription. Evidence from a small open label trial in a restricted population was encouraging, but better evidence is needed to guide clinicians and policymakers. We aimed to assess the effectiveness of daily use of D-mannose compared with placebo in preventing symptomatic UTI in women with recurrent UTI.


In this two-arm individually randomised double-blind placebo-controlled trial we included women who had had at least 2 UTis in the previous 6 months or 3 in the previous year. Women who were pregnant, breastfeeding, catheterised or who had recently started prophylactic antibiotics were excluded. Participants were randomised to 6 months of daily D-Mannose powder (2 grams) or placebo. The primary outcome was the proportion of women experiencing at least one further episode of clinically suspected UTI for which they contact ambulatory care within 6 months of study entry. Secondary outcomes included symptom burden, antibiotic usage and microbiologically proven UTI.


598 women (295 placebo, 303 D mannose) were recruited between May 2019 and January 2020 with 289 and 294 respectively included in our intention-to-treat analysis. Baseline characteristics were similar between groups. The proportion of women experiencing at least one clinically suspected UTI was 55.7% in the placebo and 51% in the D-mannose group. The unadjusted risk difference was -4.69% (95% CI -12.78% to 3.40%, p=0.257). A per protocol analysis including only women who reported taking the treatment at least 4 days a week also found no significant difference. The D-mannose group received significantly fewer days of antibiotics (adjusted median difference 3 days [95% CI 1.60 to 4.40]). Data analysis is ongoing and full secondary outcomes data will be available for presentation.


In women presenting to primary care with recurrent UTI, D-Mannose does not significantly reduce the chance of a subsequent infection in a period of 6 months of treatment.

Submitted by: 
Gail Hayward
Funding acknowledgement: 
This study is funded by the National Institute for Health Research (NIHR) School for Primary Care Research. The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care.