Preventing recurrent UTI: the options, graded honestly

Vaginal oestrogen (for women after the menopause)

What it is. A low dose of oestrogen applied directly to the vaginal tissues as a cream, pessary or ring. This is local treatment, not HRT; very little is absorbed into the bloodstream.

The evidence. Strong. Falling oestrogen after the menopause changes the tissue and bacterial balance that normally protect against infection, and restoring it locally reduces recurrent infections in randomised trials. It is recommended in both UK and American guidance for postmenopausal women with recurrent UTI.

Who it suits. Any peri or postmenopausal woman with recurrent UTI, unless there is a specific contraindication. In my practice it is one of the most consistently effective and most underused treatments on this page.

Methenamine hippurate: the antibiotic sparing preventive

What it is. A twice daily tablet that works by making the urine hostile to bacteria, rather than by acting as an antibiotic. Because it is not an antibiotic, it does not drive resistance.

The evidence. Strong and recent. The UK ALTAR trial, published in the BMJ in 2022, randomised women with recurrent UTI to methenamine or to daily low dose antibiotics for a year and found methenamine was non-inferior: it prevented infections about as well as the antibiotics did. On the strength of this, NICE now includes methenamine as an option for prevention.

Taken with vitamin C. Methenamine only works in acidic urine, where it converts into the formaldehyde that kills bacteria. For that reason I typically pair it with a high dose of vitamin C, which is intended to keep the urine acidic enough for the drug to do its job. See vitamin C below.

Who it suits. Women who want an effective preventive without long term antibiotics. It requires reasonable kidney function and is not suitable in pregnancy.

Vitamin C (ascorbic acid)

What it is. A high dose vitamin supplement, used here not as a general immune tonic but for a specific purpose: making the urine more acidic.

Why I use it. Methenamine depends on acidic urine. In an acidic bladder it converts into formaldehyde, which kills bacteria; if the urine is alkaline, much less of that conversion happens and the drug works less well. Pairing high dose vitamin C with methenamine is intended to hold the urine in the range where the drug is effective, and it is how I typically prescribe the combination.

The evidence, honestly. The pharmacological logic is sound and long established. Studies of how reliably ascorbic acid actually lowers urine pH have been mixed, with some finding a modest effect and others little change, so this is a rational and widely used pairing rather than a proven one. As a standalone UTI preventive, without methenamine, vitamin C has weak and inconsistent evidence and I would not rely on it.

Cautions. High doses of vitamin C increase the amount of oxalate in the urine, which matters if you have had calcium oxalate kidney stones or are prone to them. Tell me if you have any history of stones, and dose is something to agree at consultation rather than to guess at.

Who it suits. Chiefly patients taking methenamine. Not a substitute for it, and not a treatment I would use on its own.

Antibiotic strategies, used well

What they are. Antibiotics still have a legitimate place, used deliberately rather than reactively. The main structured approaches are a single low dose taken after intercourse where infections follow sex, a self start pack kept at home and begun promptly at the first sign of a confirmed pattern of infection, and continuous low dose prophylaxis for a defined period with a planned review date.

The evidence. All three reduce infections in trials; continuous prophylaxis is effective but its benefit fades after stopping, and it carries the costs of long term antibiotic exposure. The skill is in choosing the least antibiotic that achieves control, and always with an exit strategy.

Who they suit. Post-coital dosing for clearly sex related infections. Self start for infrequent but definite episodes. Continuous prophylaxis where other measures have failed or while an underlying cause is being treated.

D-mannose

What it is. A sugar, taken as powder or capsules, which stops E. coli sticking to the bladder wall.

The evidence. Weaker than most people assume. Early small studies were promising, but the largest and best conducted trial to date, published in JAMA Internal Medicine in 2024, randomised over 500 women in UK primary care to daily D-mannose or placebo and found no meaningful reduction in infections. Trial evidence does not currently establish it as a proven preventive, and I would not want you to believe otherwise.

My view. I do generally suggest D-mannose, and it is worth being clear why. A negative result in a broad primary care population does not exclude benefit in the particular women who come to a specialist clinic, and a substantial number of my patients report a genuine difference. It is inexpensive, well tolerated and carries minimal risk. So I treat it as a reasonable thing to try alongside the measures that carry stronger evidence, never instead of them, and we review honestly after a few months whether it is earning its place for you.

Who it suits. Most patients who want to add a low risk measure, particularly while the treatments with stronger evidence are being established.

Cranberry, and why the form matters

What it is. Cranberry contains proanthocyanidins (PACs), compounds that reduce the ability of E. coli to stick to the bladder wall. These are available as juice, or as standardised capsules and tablets.

The evidence. Modestly positive, and dose dependent. The 2023 Cochrane review of more than fifty trials concluded that cranberry products probably do reduce symptomatic infections in women with recurrent UTI. A 2024 meta-analysis went further and identified a threshold: a daily intake of at least 36 mg of proanthocyanidins reduced infection risk by around 18 per cent, while lower doses showed no significant benefit, and products needed to be taken for at least three months.

A word about cranberry juice. This is where I would urge caution. Reaching a meaningful PAC dose through juice means drinking large volumes of a drink that is typically heavily sweetened, and I do not think that is a good trade. The sugar load is substantial, it is a poor idea for anyone with diabetes or at risk of it, and glucose in the urine does bacteria no harm at all. My view is that large volumes of sweetened cranberry juice are more likely to work against you than for you. If you want to use cranberry, use a standardised extract where you can see the PAC content on the label.

Who it suits. A reasonable low risk adjunct for women with recurrent UTI, taken as a standardised extract at an adequate dose and given a few months to show whether it helps. Not a substitute for finding the cause.

Probiotics

What they are. Oral or vaginal lactobacillus preparations intended to restore the protective bacterial population of the vagina and gut.

The evidence. Limited. Trials have been small and inconsistent, and no single product has proven itself well enough for me to name one on the strength of the data alone.

My view. The rationale is sound: recurrent UTI is closely tied to the loss of protective vaginal lactobacilli, particularly after the menopause and after repeated courses of antibiotics, and restoring that flora is a logical target. Many patients report benefit, the risk is minimal, and I commonly suggest probiotics as part of a broader plan, particularly following antibiotic treatment. What I cannot tell you is that a trial proves it.

Who they suit. A reasonable adjunct for most patients, especially after antibiotic courses. Not a substitute for treating the underlying cause.

Bladder instillations (intravesical treatment)

What they are. A course of treatments in which a solution of hyaluronic acid and chondroitin sulfate is placed directly into the bladder through a fine catheter, to replenish the protective GAG layer that lines the bladder wall. Each instillation takes a few minutes in clinic. I offer this treatment.

The evidence. Encouraging. Randomised studies and pooled analyses show reduced infection frequency and longer infection free intervals in women with recurrent UTI, with very few side effects. The evidence base is smaller than for the options above, which is why I position it after simpler measures, but for the right patient the results can be substantial.

Who it suits. Women with recurrent or persistent infection despite first line measures, and selected patients with chronic bladder pain where the protective lining appears compromised.

The sublingual UTI vaccine (MV140, Uromune)

What it is. A daily spray under the tongue, taken for three months, containing inactivated bacteria that train the immune system to resist the common causes of UTI.

The evidence. Promising. A randomised placebo controlled trial published in NEJM Evidence found a large reduction in infections, with over half of vaccinated women infection free in the following nine months compared with a quarter on placebo, and real world studies including UK cohorts support this. It is not yet licensed in the UK and is prescribed by specialists on a named patient basis, so it remains an emerging option rather than routine care.

Who it suits. Selected patients with troublesome recurrent UTI, particularly where other measures have failed or are unsuitable. I am happy to discuss and arrange it where appropriate.