D-Mannose
What it is
Evidence has weakened considerably. The large MERIT trial (JAMA 2024, 598 women in UK primary care) found D-mannose did NOT significantly reduce recurrent UTIs versus placebo. Earlier small trials had suggested benefit comparable to low-dose antibiotics, but these were lower quality. It works in principle by preventing E. coli from adhering to the bladder wall. Very safe with no significant side effects — may still be worth a trial alongside cranberry extract, but is no longer first-line evidence-based prevention.
Dose
2 g/day for prevention (note: 2024 MERIT trial found no benefit at this dose); 2 g × 3 daily at symptom onset
Time of day & tips
Take with a full glass of water at any time of day. Can be taken with or without food. No major drug interactions. Can be combined with cranberry extract. Not a substitute for medical evaluation of recurrent UTIs.
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