Bacterial Vaginosis (BV): Which Test Do You Need, and What Happens Next?

Bacterial vaginosis is not an infection with one germ but a shift in the vaginal ecosystem: the protective Lactobacillus species that keep the pH acidic are replaced by an overgrowth of anaerobes — Gardnerella vaginalis, Atopobium vaginae, Megasphaera and others. The result is thin grey-white discharge, a fishy odor that is strongest after sex, and sometimes mild irritation. It is the most common cause of vaginal symptoms in women of reproductive age, and roughly a third of women have it at any given time, often without symptoms.

BV is not classified as a sexually transmitted infection, but it behaves like one in important ways: it is associated with new or multiple partners, with not using condoms, with douching, and it raises the risk of acquiring HIV, chlamydia, gonorrhea, trichomonas and herpes. It also matters in pregnancy, where symptomatic BV is linked to preterm birth and is treated.

The diagnostic problem is that BV, yeast infection and trichomoniasis produce overlapping symptoms, and over-the-counter antifungals treat only one of them. In studies of women who self-diagnosed a "yeast infection," about half had something else — most often BV. Antifungals do nothing for BV, and the delay lets it persist. That is why the useful test is one that names the organism rather than one that confirms a guess.

Clinicians diagnose BV in three ways. Amsel criteria — three of four bedside findings (thin grey discharge, vaginal pH above 4.5, a fishy odor when a drop of potassium hydroxide is added, and "clue cells" under the microscope) — need an exam and a microscope. The Nugent score, a Gram stain of the discharge graded in a lab, is the reference standard but is slow and mostly used in research. Nucleic acid amplification tests (NAATs) detect the DNA of the BV-associated bacteria and the protective lactobacilli, usually together with Candida and Trichomonas on the same swab, with sensitivity and specificity around 90–97% against the Nugent score — and they work on a self-collected swab, which is what makes testing without a pelvic exam possible.

The CDC's guidelines recommend NAATs for women with symptoms; their accuracy in women without symptoms is not established, and asymptomatic BV in non-pregnant women is not usually treated anyway. Culture of Gardnerella is not recommended — the organism is present in many women without BV, so growing it proves nothing.

TestWell's Vaginitis Panel ($149.99) is a NAAT for all three causes — bacterial vaginosis, Candida (including the species that resist standard antifungals) and Trichomonas vaginalis — on one swab you collect yourself in a private restroom at Quest, with results in 1–3 business days. It is the same technology clinics send out; the difference is that no visit or exam stands between you and the result.

Vaginal pH strips sold in pharmacies test one of the four Amsel criteria. A pH above 4.5 is consistent with BV or trichomoniasis and argues against a yeast infection (which keeps the pH normal) — useful for steering away from an antifungal, but it cannot distinguish BV from trich, and blood, semen and recent douching all raise the pH falsely. Mail-in kits that run a NAAT on a swab you collect at home are the same test as the lab's, with the added days of shipping and the loss of a lab's chain of custody; a positive result still needs a prescription from a clinician. How to test for BV compares the three routes in detail.

A positive BV result with symptoms is treated — the CDC's recommended regimens are oral metronidazole for seven days, metronidazole vaginal gel for five days, or clindamycin vaginal cream for seven days, with tinidazole, secnidazole and oral or vaginal clindamycin as alternatives. Any of these is a short prescription from your own clinician or a telehealth visit, with the lab report in hand; cure rates are 70–80% at one month. Avoid sex or use condoms during treatment, and skip douching, which raises the chance of relapse.

A positive yeast result is treated with an antifungal (and the species matters: Candida glabrata, which the panel identifies, often does not respond to the usual fluconazole). A positive trichomonas result is a sexually transmitted infection — you and your partner are both treated, and testing for chlamydia and gonorrhea is sensible. All three negative with persistent symptoms points elsewhere: irritant or allergic vaginitis, atrophic changes after menopause, a urinary infection, or herpes, and that is a clinician's evaluation.

No follow-up test is needed if symptoms resolve. The frustrating feature of BV is recurrence — more than half of women have another episode within a year. Options a clinician may use for recurrent BV include a longer course followed by twice-weekly metronidazole gel for several months, and boric acid; the 2021 CDC guideline does not recommend treating male partners, but a 2025 randomized trial found that treating the male partner with oral and topical metronidazole at the same time cut recurrence substantially, and guidelines are expected to update. Ask about it if you have had BV more than twice.

• Pelvic or lower abdominal pain, fever, or pain with sex — possible pelvic inflammatory disease, a same-day evaluation.
• Pregnancy, or the possibility of it — symptomatic BV in pregnancy is treated, the drug choice changes, and the test should go through your obstetric clinician.
• Bleeding between periods or after sex, sores or blisters, or symptoms after a possible exposure to an STI — testing is still right, but an exam is too.
• A first episode of symptoms in someone under 18, or recurrent symptoms that have not responded to two courses of treatment.