D-Mannose

What it is

D-mannose is a simple sugar related to glucose that occurs naturally in small amounts in some fruits. Much of a supplemental dose passes into the urine rather than being used for energy.

How it works

Many UTIs are caused by E. coli bacteria that grip the bladder wall using tiny hair-like structures. D-mannose that reaches the urine is thought to act as a decoy, binding to those structures so bacteria get flushed out rather than sticking. That mechanism holds up in the lab, but in the largest real-world trial, it didn't translate into fewer infections.

What it's been studied for

Commonly taken for urinary tract support, especially by women with repeated urinary tract infections (UTIs).

What the evidence shows

Mixed, and the best trial was negative: earlier small, mostly open-label trials looked encouraging, but a large 2024 placebo-controlled trial of nearly 600 women with recurrent UTIs in UK primary care found daily D-mannose no better than placebo at preventing further medically attended UTIs. The honest read is that the strongest evidence doesn't support it for this use.

Who should consider it

It's marketed to women with repeated UTIs looking for a non-antibiotic option. Given the negative large trial, we include it for transparency more than as a recommendation. If you get frequent UTIs, work with your provider on an evaluation and prevention plan, which may include evidence-based options beyond supplements.

Amounts commonly studied

Studies typically used 2 grams per day of D-mannose powder dissolved in water, taken for about six months in prevention trials.

How to take it

Studies typically used 2 grams per day dissolved in water, taken for about six months in prevention trials. If you choose to try it, don't use it to self-treat an active infection — see your provider for testing and treatment. People with diabetes should talk to their provider before starting.

Forms & absorption

Sold as powder to dissolve in water and as capsules, sometimes combined with cranberry. Powder makes larger doses easier to take.

Food sources

Small amounts occur naturally in fruits such as cranberries, apples, peaches and oranges — far less than the amounts studied in supplements.

Safety & interactions

Generally well tolerated; bloating and loose stools can occur, especially at higher doses. Because it's a sugar, people with diabetes should check with their provider and monitor their blood sugar. UTI symptoms — burning, urgency, fever, back or side pain, or blood in the urine — need prompt medical care, and UTIs during pregnancy always need a provider's attention, since untreated infections can spread to the kidneys.

Common questions

Does D-mannose prevent UTIs?

The best evidence says it doesn't help much: a large 2024 trial in nearly 600 women with recurrent UTIs found daily D-mannose no better than placebo. Earlier positive studies were smaller and less rigorous.

Can I use it to treat a UTI I have right now?

No — a suspected UTI needs medical evaluation and, usually, treatment. Untreated infections can spread to the kidneys, especially if you have fever or back pain.

Is it safe if I have diabetes?

Much of it passes into the urine, but it's still a sugar and some is absorbed. Check with your provider and monitor your blood sugar if you decide to try it.