Bacterial vaginosis (BV) is not classified as a sexually transmitted infection, but it's strongly linked to sexual activity. It comes from an imbalance in the bacteria that normally live in the vagina rather than a single pathogen passed between partners. Women who have never had sex rarely get it, which is where the confusion comes from.
with the right treatment
testing, not symptoms, decides
| Item | Value |
|---|---|
| Curable? | yes — with the right treatment |
| Tested by | exam + lab |
| Often | no symptoms |
| If you may have it | get tested — testing, not symptoms, decides |
So is BV an STD or not?
No — BV isn't a traditional STI like chlamydia or gonorrhea, where one specific organism is transmitted during sex. It's an ecosystem shift: the protective Lactobacillus species that normally dominate the vagina get crowded out by a mix of anaerobic bacteria CDC. There's no single "BV germ" you catch. The line isn't perfectly clean, though. BV is clearly associated with sexual activity — new or multiple partners, and partners of any sex, all raise the risk — and it's rarely seen in people who have never been sexually active. It sits in a gray zone: sex-associated, but not sexually transmitted in the classic sense.
What BV actually is
A healthy vagina is acidic, kept that way by lactobacilli that produce lactic acid and hydrogen peroxide. That acidity discourages overgrowth of less friendly bacteria. In BV, the lactobacilli decline and anaerobes take over, the pH climbs, and the byproducts of those anaerobes create the hallmark symptoms. It's the most common vaginal condition in women ages 15 to 44, so if you've been told you have it, you're in very large company.
Symptoms — and the silent reality
The classic signs are a thin white or gray discharge and a strong, fishlike odor that's often most noticeable after sex. Some people also notice itching, burning around the vulva, or burning when they urinate. Many people with BV have no symptoms at all and find out only on a routine exam or test. The fishy smell is the most specific tip-off — it comes from amines released by the anaerobic bacteria, and it gets stronger when semen, which is alkaline, raises the vaginal pH. For a fuller breakdown of what to look and smell for, see our guide to bv symptoms.
How BV spreads
Because it isn't a single transmissible organism, "spread" isn't quite the right word, but the things that disrupt the vaginal balance are well documented. Risk goes up with douching, which flushes out protective bacteria, and with not using condoms or having new or multiple sex partners, including female partners. Toilet seats, bedding, towels, and swimming pools do not cause BV. You cannot pick it up from a surface.
Female partners matter too. Two women can repeatedly share the same disrupted vaginal flora, part of why BV recurs so stubbornly in some couples.
How BV is tested
Diagnosis is usually quick and low-tech. Clinicians use one of three approaches: the Amsel criteria (a diagnosis requires at least three of four findings — thin discharge, clue cells under the microscope, a vaginal pH above 4.5, and a positive whiff/fishy-odor test); the Nugent score, which grades bacteria on a Gram-stained slide and is the reference standard; or an FDA-cleared molecular test CDC STI guidelines, 2021.
In practice, testing means a simple sample — a quick pelvic exam, a self-collected swab, or in some settings a lab panel — with results usually back within a few days. It's free or low-cost at health departments, Planned Parenthood, and Title X clinics. If you've had a new partner or possible exposure to other infections, check the timing on when to test after exposure and get tested for the standard STIs at the same visit, since BV symptoms overlap with several of them. If you're weighing at-home versus clinic options, you can compare testing providers.
How BV is treated
BV is treated with antibiotics, and the current standard regimens are well established:
- Metronidazole 500 mg orally twice daily for 7 days.
- Metronidazole 0.75% gel, one 5 g applicator intravaginally once daily for 5 days.
- Clindamycin 2% cream intravaginally at bedtime for 7 days.
A couple of practical points trip people up. Per the 2021 guidelines, you no longer need to avoid alcohol while taking metronidazole; there's no convincing evidence of the reaction people were long warned about. Clindamycin cream and ovules are oil-based, so they can weaken latex condoms — use a backup method while you're using them. Whatever you're prescribed, finish the entire course even after you feel better. Stopping early is a common reason BV bounces back.
Almost everyone asks whether their partner needs treating. For male partners, routine treatment is not recommended; it doesn't prevent recurrence. With female partners the picture is less settled, so ask your clinician directly.
What happens if BV is left untreated
BV isn't just an annoyance. The loss of protective lactobacilli changes the vaginal environment in ways that raise real risks:
- Higher risk of acquiring or transmitting HIV and other STIs — a meta-analysis of more than 30,000 women found BV raised the risk of acquiring HIV by about 60% (RR 1.61) Atashili et al..
- In pregnancy, BV is linked to preterm delivery (giving birth too early) and low birth weight, both of which carry health consequences for the baby.
- Greater susceptibility to pelvic infections after gynecologic procedures.
None of this means BV is dangerous in the way a serious infection is, but it's a reason to treat it rather than wait it out, especially during pregnancy or if you're at risk for HIV.
Why BV keeps coming back
BV comes back often. Standard antibiotics cure most acute episodes — roughly 80 to 90% — but it returns in up to 60% of women within twelve months SASGOG, which reflects how the condition behaves rather than any failure of treatment. When someone has three or more episodes in a year, that's defined as recurrent BV, usually managed with a months-long maintenance regimen rather than just repeating a single course. Our guide to recurrent bv covers what that looks like.
How to lower your risk
You can't always prevent BV, but a few habits meaningfully reduce the odds:
- Don't douche — it strips out the protective bacteria you want to keep.
- Use condoms correctly every time; consistent condom use is associated with lower BV risk and also protects against the STIs that share its symptoms.
- Limit the number of sex partners.
- Get tested routinely, which catches the infections that have no symptoms at all.
For a fuller checklist, see our guide on how to prevent bv.
When to see a clinician
See a clinician if you notice an unusual discharge, a new fishy odor, itching, or burning, especially if symptoms are new or different from anything you've had before. Get checked promptly if you're pregnant, if symptoms recur, or if you've had a new partner and want to rule out other STIs at the same time. A BV diagnosis is common and treatable. Clinics handle it every single day, and it says nothing about you as a person.