The Urinary Microbiome, Explained: Your Bladder Is Not Sterile

The old belief: a sterile bladder

For most of modern medicine, healthy urine was thought to contain no bacteria. That belief came largely from the standard urine culture, a test designed to detect the fast-growing bacteria that cause typical infections. If nothing grew, the urine was called sterile. The test was never designed to find slow-growing or hard-to-culture microbes.

What changed

Over the past two decades, researchers began using DNA sequencing, which identifies bacteria by their genetic material, and expanded culture techniques that give microbes more time and different conditions to grow. Using samples collected directly from the bladder by catheter, they found that many people without infections have a small but real community of microbes in their bladder. This community is now called the urinary microbiome or urobiome.

Who lives there?

In women, the bladder microbiome often includes Lactobacillus species, the same group that commonly dominates a healthy vagina, along with Gardnerella, Streptococcus and many others. The community is much less dense than the gut microbiome, and its makeup varies from person to person, with age, hormones and other factors.

What does it have to do with bladder symptoms?

This is the exciting and uncertain part. Studies, including research from the US Pelvic Floor Disorders Network, have compared the urinary microbiome of women with urinary incontinence and women without it. Researchers have reported differences in the types and diversity of bacteria, and some community patterns have been linked with more severe urge symptoms.

Several explanations are possible:

• Certain microbes might irritate the bladder lining or nerves, contributing to urgency.
• Bladder symptoms, infections and treatments might change the microbiome, rather than the other way round.
• Age, menopause and hormone levels might affect both the microbiome and the bladder independently.

At this stage, the research shows associations. It does not prove that changing the microbiome will improve symptoms.

The vaginal connection

The vagina, urethra and bladder are close neighbors, and microbes move between them. A healthy vaginal microbiome dominated by lactobacilli produces lactic acid and creates an environment that tends to discourage unwanted bacteria. After menopause, lower estrogen levels often reduce lactobacilli, which is one reason urinary infections and bladder symptoms become more common later in life. Clinicians sometimes prescribe vaginal estrogen after menopause partly for this reason.

Can you change your urinary microbiome?

Researchers are testing several approaches:

• Probiotics: oral and vaginal lactobacillus products are being studied. Results are strain-specific and mixed. A 2015 Cochrane review found no clear evidence that probiotics, as studied at the time, prevent UTIs.
• Cranberry: it does not change the microbiome so much as make it harder for some bacteria to attach to the bladder wall. A 2023 Cochrane review found cranberry products probably reduce recurrent UTIs in women.
• Vaginal estrogen after menopause: prescribed by clinicians for genitourinary symptoms.
• Avoiding unnecessary antibiotics: antibiotics can disturb microbial communities.

What it means for supplements

Supplements such as FemiCore are built on urinary microbiome research. The science is a reasonable starting point, but there is a gap between “women with incontinence have different bladder bacteria” and “this capsule will improve bladder control.” Before buying any microbiome product, look for disclosed strains and CFU counts, and evidence on the finished product. We apply these questions in our FemiCore research review.

Simple habits that support a healthy urinary environment

• Drink enough fluid during the day so urine is pale.
• Do not hold urine for very long periods.
• Urinate after sex.
• Avoid douching and scented intimate products.
• Use antibiotics only when prescribed.
• Seek care promptly for UTI symptoms such as burning, fever or back pain.

The bottom line

Discovering the urinary microbiome has changed how scientists think about the bladder, and it may lead to new treatments. For now, it is a field of promising questions rather than settled answers. Proven steps such as pelvic floor training and bladder retraining remain the foundation of care.

Frequently asked questions

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Last reviewed and updated: October 20, 2026.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.