A randomized clinical trial evaluated the effectiveness of D-mannose in preventing recurrent urinary tract infections (UTIs) in women. The study involved 598 women aged 18 years or older with a history of recurrent UTIs, recruited from 99 primary care centers in the UK. Participants were randomly assigned to receive either D-mannose (2 g/day) or a placebo for 6 months. The primary outcome was the proportion of women who experienced a medically attended UTI within 6 months of randomization. The results showed no significant difference between the D-mannose and placebo groups, with 51.0% and 55.7% of participants, respectively, experiencing a UTI. Secondary outcomes, including symptom duration, antibiotic use, time to next UTI, and hospital admissions, also showed no significant differences between the groups. The study found that daily D-mannose did not reduce the proportion of women with recurrent UTIs who experienced a subsequent UTI. Therefore, D-mannose should not be recommended for prophylaxis in this patient group. The study highlights the need for further research into alternative treatments for recurrent UTIs, particularly in primary care settings. The findings suggest that while D-mannose may offer some benefit in certain contexts, it is not effective in preventing recurrent UTIs in the general population of women with a history of recurrent UTIs. The study also notes that the high cost of D-mannose and the lack of evidence supporting its use in primary care settings mean that it should not be recommended for prophylaxis in this patient group. The study was funded by the National Institute for Health and Care Research (NIHR) School for Primary Care Research.A randomized clinical trial evaluated the effectiveness of D-mannose in preventing recurrent urinary tract infections (UTIs) in women. The study involved 598 women aged 18 years or older with a history of recurrent UTIs, recruited from 99 primary care centers in the UK. Participants were randomly assigned to receive either D-mannose (2 g/day) or a placebo for 6 months. The primary outcome was the proportion of women who experienced a medically attended UTI within 6 months of randomization. The results showed no significant difference between the D-mannose and placebo groups, with 51.0% and 55.7% of participants, respectively, experiencing a UTI. Secondary outcomes, including symptom duration, antibiotic use, time to next UTI, and hospital admissions, also showed no significant differences between the groups. The study found that daily D-mannose did not reduce the proportion of women with recurrent UTIs who experienced a subsequent UTI. Therefore, D-mannose should not be recommended for prophylaxis in this patient group. The study highlights the need for further research into alternative treatments for recurrent UTIs, particularly in primary care settings. The findings suggest that while D-mannose may offer some benefit in certain contexts, it is not effective in preventing recurrent UTIs in the general population of women with a history of recurrent UTIs. The study also notes that the high cost of D-mannose and the lack of evidence supporting its use in primary care settings mean that it should not be recommended for prophylaxis in this patient group. The study was funded by the National Institute for Health and Care Research (NIHR) School for Primary Care Research.