Bacterial Vaginosis (BV): Symptoms, Causes & Treatment

If you've noticed an unusual thin discharge or a fishy odor "down there," you're not being weird for wondering what it is. Bacterial vaginosis (BV) is the single most common vaginal condition in women of reproductive age, and it's often confused with a yeast infection. The two feel and look completely different, need completely different treatments, and figuring out which one you have matters.

This guide covers what BV actually is, how to recognize it, what causes the microbiome shift behind it, how it's diagnosed and treated, and what you can do to reduce your chances of it recurring.

This article is educational, not medical advice. Symptoms overlap with other conditions and self-diagnosis is unreliable — please see a clinician for testing. We're the team behind Vyve, a private AI cycle tracker; Vyve is a tracking tool, not a diagnostic one.

What is bacterial vaginosis, exactly?

Bacterial vaginosis is a shift in the vaginal microbiome — the protective lactobacilli that keep the vagina acidic decrease, and other bacteria (like Gardnerella) overgrow. The result is a change in vaginal pH from its normally acidic state to a more alkaline one, which produces the characteristic discharge and odor.

BV isn't an "infection" in the way strep throat is. It's a microbial imbalance. It's not typically considered a sexually transmitted infection either, though sexual activity is one of the biggest risk factors because sex introduces new microbes and changes vaginal chemistry. Anyone with a vagina can get BV, and about a third of women of reproductive age have it at any given time — many without knowing.

Common BV symptoms

Interestingly, up to half of BV cases cause no noticeable symptoms. When they do, the classics are:

• Thin, watery, grayish-white or off-white discharge — the discharge is one of the biggest tells.
• A fishy odor that often becomes more noticeable after sex or during your period, because both raise vaginal pH.
• Mild burning during urination in some cases.
• Mild itching or irritation, though this is far less common than in yeast infections.

Compare this to milky white discharge that's normal in some cycle phases, or the thick "cottage cheese" texture of a yeast infection. If you're not sure what your discharge means, our guides to white discharge after your period and brown discharge before your period may help — but for suspected BV, testing beats guessing.

BV vs yeast infection at a glance

These are archetypes — real cases sometimes blur the lines, and it's possible to have both at once. That's another reason to be tested rather than to self-treat with over-the-counter antifungals.

What causes BV?

BV happens when the vaginal microbiome shifts out of balance. Common triggers include:

• New or multiple sexual partners — sex introduces new microbes.
• Unprotected sex — semen is alkaline and can shift vaginal pH.
• Douching — arguably the single most disruptive habit. Douches strip protective lactobacilli.
• Scented soaps, wipes, sprays or feminine washes used on the vulva or in the vagina.
• Antibiotics that disrupt normal flora.
• Hormonal changes, including around periods.
• Copper IUDs in some people.
• Smoking.

Things that do not cause BV: normal hygiene, tampons, unscented pads, being sexually active in general, or "not cleaning enough." The vagina cleans itself and doesn't need help from products marketed to it.

BV is a microbiome imbalance, not a hygiene failure. The single most helpful thing many people can do is stop douching.

How BV is diagnosed

A clinician typically diagnoses BV by:

• A brief history and pelvic exam to look at discharge and vulvar tissue.
• A pH test — vaginal pH above 4.5 suggests BV.
• The "whiff test" — a drop of potassium hydroxide added to a discharge sample releases a fishy odor if BV is present.
• Microscopy — looking at cells under a microscope for "clue cells" (vaginal cells coated with bacteria), a hallmark of BV.
• DNA-based lab tests for BV-associated bacteria, increasingly used and highly accurate.

Diagnosis is quick — usually one appointment. Home vaginal pH strips exist but can't distinguish BV from other causes of pH change.

Treatment options

BV is treated with antibiotics — usually metronidazole or clindamycin, given as oral pills or as vaginal gels/creams. Both are effective and are chosen based on your history, allergies, pregnancy status and preference. Symptoms often improve within a few days, but you should finish the whole course to reduce the chance of recurrence. We're not naming doses or brands on purpose — prescribing is your clinician's job.

Over-the-counter yeast infection treatments do not treat BV. If you self-treat for yeast when you actually have BV, symptoms won't improve, and treatment will be delayed.

Recurrent BV

Here's the frustrating truth: BV recurs in more than 50% of cases within a year of treatment. If BV keeps coming back, a clinician may discuss longer antibiotic courses, alternate regimens, maintenance therapy (regular use over months), or interventions targeting the vaginal microbiome. Research on vaginal probiotics is ongoing but not yet conclusive as a standalone cure. A newer approach — treating male sexual partners with certain antibiotics — has shown promise in specific studies and is under discussion.

If you have recurrent BV, ask your clinician about screening for other conditions that can perpetuate it, and about a longer-term plan rather than a one-off course.

Prevention

• Don't douche. Ever. The vagina is self-cleaning.
• Skip scented soaps, wipes, sprays and "feminine hygiene" products on the vulva and in the vagina.
• Use condoms with new partners.
• Wipe front to back to avoid introducing bacteria from the bowel.
• Wear breathable cotton underwear and change out of damp workout clothes promptly.
• Consider unscented menstrual products.

BV and pregnancy

BV in pregnancy is associated with a higher risk of preterm birth, low birth weight and pregnancy loss in some studies. Pregnant people with BV symptoms should be evaluated and treated — antibiotic choice varies during pregnancy, and your obstetrician will pick the right regimen.

When to see a doctor

See a clinician if you have:

• Unusual discharge, especially with a fishy odor.
• Symptoms that don't improve after over-the-counter yeast treatment (which suggests it's not yeast).
• Recurrent BV or vaginal infections.
• BV symptoms during pregnancy.
• Any pelvic pain, fever or concerning bleeding.

How Vyve helps track BV patterns

Vyve can help you keep an honest record of discharge, odor, cycle timing and any recurring vaginal-health symptoms over time. Recurring BV is common enough that having months of data — how it relates to your cycle, sex, antibiotic courses or hormonal shifts — makes a real difference at your appointment.

Vyve is a tracking tool, not a diagnostic one. It won't diagnose BV. What it does is give you and your clinician a clear picture of patterns that would otherwise be hard to remember.

Frequently asked questions

What is bacterial vaginosis?

The most common vaginal condition in women of reproductive age, caused by a shift in vaginal bacteria — protective lactobacilli decrease and other bacteria overgrow, producing thin discharge and a fishy odor.

What are the symptoms of BV?

Thin, grayish-white discharge and a strong fishy odor, sometimes with mild burning during urination. Half of cases cause no symptoms.

What causes BV?

A shift in the vaginal microbiome, often triggered by new sexual partners, unprotected sex, douching, scented products, antibiotics, hormonal changes or smoking. Not caused by poor hygiene.

How is BV different from a yeast infection?

BV causes thin grayish discharge and a fishy odor with little itching. Yeast causes thick white cottage-cheese-like discharge with intense itching and no odor. Treatments are different, so testing beats guessing.

How is BV treated?

With antibiotics — usually metronidazole or clindamycin, oral or vaginal. Symptoms improve within days, but finish the full course. BV recurs in over half of cases, so ask about a longer plan if it keeps coming back.