SupplementModerate evidenceImmunity

D-mannose

Simple sugar with RCT signal for UTI prevention non-inferior to low-dose nitrofurantoin in recurrent uncomplicated UTI.

Why

D-mannose is a simple monosaccharide that is absorbed and excreted unchanged in urine. The Kranjčec 2014 RCT in 308 women with recurrent UTI compared D-mannose 2 g/day with nitrofurantoin 50 mg/day prophylaxis. Both significantly reduced UTI recurrence vs control, with D-mannose having far fewer side effects. Subsequent meta-analyses confirm the prevention signal in recurrent uncomplicated UTI; D-mannose is not for treating an established UTI.

How it works

Binds the FimH lectin on Type-1 pili of uropathogenic E. coli (the cause of ~80% of UTIs), blocking adherence to bladder uroepithelium. Saturating urinary D-mannose levels coat the bacterial pili. Pathogen is then mechanically washed out with normal voiding.

Expected onset · Prevention effect assessed over 6 months

How to take

Dosage

Prevention: 2 g/day (e.g. one teaspoon of powder in water). Acute symptom onset: 2 g three times daily for 3 days (rescue regimen, clinical evaluation still needed).

Timing

With water; spaced if multiple daily doses

On the label

'D-mannose' powder (most cost-effective) or capsules with stated grams per serving. Pharmaceutical-grade is preferred.

Ideal for

Adult women with recurrent uncomplicated UTI prevention; particularly attractive when antibiotic-stewardship is a priority.

Safety

Not for treatment of an established UTI without medical evaluation. D-mannose does not kill bacteria, only mechanically reduces adherence. Mild GI upset (bloating, soft stool) at higher doses. D-mannose is poorly absorbed. Mild glucose-equivalent calorie load. Note for strict glycaemic management. Pregnancy: limited data; coordinate with the prescribing clinician for recurrent UTI in pregnancy.

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Evidence

At a glance

Kranjčec 2014 World J Urol RCT (n=308): D-mannose 2 g/day reduced UTI recurrence to 14.6% vs 60.1% on no prophylaxis, non-inferior to nitrofurantoin 50 mg/day (20.4%) with significantly fewer adverse events. Lenger 2020 Am J Obstet Gynecol meta-analysis: 8 RCTs supported reduced UTI risk in recurrent UTI populations.

Where to get it

Shop D-mannose on Amazon

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