Can BV Cause A Positive Chlamydia Test?

No: bacterial vaginosis (BV) does not cause a positive chlamydia test. The test used in the UK detects the genetic material of Chlamydia trachomatis itself, and the bacteria that overgrow in BV are not picked up by it, so a positive result means chlamydia was found. The two are connected, but the other way round: BV, and the loss of the protective lactobacilli that comes with it, makes chlamydia easier to catch if you are exposed to it.^{1, 2} The condition itself is explained in what is the main cause of BV.

Sources checked on 29 October 2026.

Can BV cause a false positive chlamydia test?

Not in any documented way. Chlamydia tests (NAATs, or nucleic acid amplification tests) detect genetic material from the bacterium Chlamydia trachomatis in a urine or swab sample; the mixed bacteria of BV are not what the test looks for.

False positives do happen, rarely, and their causes are practical rather than biological:

• Lab handling errors or a contaminated sample
• Leftover chlamydia DNA in the weeks after a course of antibiotics, because the test can detect fragments after the bacteria are dead
• Testing for cure too soon after finishing antibiotics, for the same reason
• Not following the self-test kit instructions correctly

If a result does not add up, ask for a repeat test, ideally on a different sample type.

So is BV actually linked to chlamydia, or is it a coincidence?

A 2003 study of 255 women who had recently had sex with a partner with urethritis found that those with bacterial vaginosis were 3.4 times as likely to test positive for chlamydia and 4.1 times as likely for gonorrhoea as women with normal vaginal flora, and that women carrying protective lactobacilli were less likely to be infected.² A 2023 systematic review of sequencing studies went further into which bacteria matter: women whose vaginal community was dominated by Lactobacillus iners, a less protective species, had 3.4 times the odds of chlamydia compared with women dominated by Lactobacillus crispatus, and 2.1 times the prevalence of BV, although that second estimate was not statistically significant (confidence interval 0.9 to 4.9).¹ The picture that emerges is of a vaginal environment, rather than a single bacterium, that makes chlamydia easier to acquire.

That doesn't mean BV causes chlamydia directly. BV is an overgrowth of the bacteria already living in your vagina, most often triggered by a period, a new sexual partner, douching, perfumed products or a copper coil, and it isn't classified as a sexually transmitted infection (we've gone into more detail on who's most likely to get BV in a separate post). Chlamydia trachomatis, on the other hand, is passed on through vaginal, anal or oral sex. What the research and the NHS describe is a vagina made less acidic, with fewer of the protective lactobacilli that normally keep harmful bacteria in check.³ That leaves you more vulnerable to catching an STI like chlamydia if you're exposed to it.

Does having BV mean you have chlamydia?

No. BV and chlamydia are separate conditions with separate causes, and having one doesn't confirm you have the other. That said, they're commonly confused because their symptoms can overlap, both are extremely common, and both often show no symptoms at all.

Side by side:

Bacterial vaginosis:

• Not sexually transmitted, though sex can trigger it
• Caused by an imbalance in your existing vaginal bacteria
• Classic sign is a thin, greyish-white discharge with a strong fishy smell, especially after sex
• Usually doesn't cause soreness or itching
• About half of women with BV have no symptoms at all

Chlamydia:

• A sexually transmitted infection caused by Chlamydia trachomatis
• Passed on through unprotected vaginal, anal or oral sex
• Can cause unusual discharge, bleeding between periods or after sex, and a burning sensation when you pee
• Most people, women and men alike, have no symptoms at all

Because the symptom pictures overlap so much, and because BV can occur at the same time as an STI, a clinician will usually test for both when you go in with unusual discharge or discomfort. Can BV mean STD? has the fuller picture.

Can BV turn into chlamydia if it's left untreated?

No. They are caused by different organisms, and one does not turn into the other however long it goes untreated. What untreated BV does do is raise your risk of picking up chlamydia or gonorrhoea if you're exposed to them, and the NHS says BV increases the risk of getting an STI, possibly because it makes the vagina less acidic and reduces its natural defences.^{2, 3}

Left untreated, BV itself can also lead to its own complications, particularly in pregnancy, where the NHS says there is a small chance of premature birth or miscarriage.³ For the fuller list of what untreated BV can lead to, and how long it tends to linger if you leave it, see What does untreated BV lead to? and What Happens If You Leave BV Too Long?

Can you have BV and chlamydia at the same time?

Yes, and it happens often enough that clinics routinely screen for both together. Since BV increases your vulnerability to chlamydia, and both conditions frequently cause no obvious symptoms, plenty of people are dealing with both without realising it. If you're diagnosed with one, it's worth asking to be tested for the other, and for STIs generally, rather than assuming a single diagnosis tells the whole story.

Treatment for the two doesn't overlap. BV is treated with antibiotic tablets, gels or creams, most often metronidazole, while chlamydia needs its own course of a different antibiotic. Having both at once just means you'll need both courses, and you'll usually be advised to avoid sex until you and any partner have finished treatment and tested clear. The UK treatment page covers the BV side.

Getting tested in the UK

If you're in the UK, testing for both BV and chlamydia is straightforward and often free. Sexual health clinics offer walk-in testing for both without a referral, GPs can test for BV, as how BV itself is tested explains, and free NHS chlamydia self-test kits are available through some pharmacies and sexual health clinics, with free postal kits specifically for under-25s.⁴ Some pharmacies also sell self-test kits if you'd rather test privately. Whichever route you take, if you get a positive result for either infection, your recent sexual partners will need to be tested too, since chlamydia in particular is easily passed on without either person realising.⁴ Pelvic pain, fever, or bleeding between periods or after sex are not BV symptoms: see a GP or sexual health clinic, or call NHS 111, rather than wait.

What we don't know

Whether BV causes the extra chlamydia risk or shares its causes: the 255-woman study was a snapshot of women already exposed, and the L. iners link to BV itself was not statistically significant.^{1, 2} Whether a course of antibiotics for BV lowers the chance of catching chlamydia: no trial we found has tested it. How often chlamydia NAATs give a false positive in UK practice: the NHS page gives no rate, only the advice to retest where needed.⁴

Frequently asked questions

Why did I test positive for chlamydia when my partner tested negative?

It isn't proof that someone's been unfaithful. Timing matters: the NHS says chlamydia symptoms can start from a week to several months after infection, and a test taken very soon after exposure can miss an early infection, so partners tested at different points can get different results.⁴ Not all tests are equally sensitive, and a low bacterial load can be missed. Chlamydia can also sit in the throat or rectum, areas that aren't always swabbed in a standard test, so a negative genital result doesn't always mean a person is infection-free. Reinfection or a new exposure is possible too, but it's one of several explanations, not the default assumption. Both partners retesting, including at additional sites if relevant, is a more useful next step than jumping to conclusions.

What are the signs of chlamydia to watch for?

Most people with chlamydia have no symptoms whatsoever, which is exactly why regular testing matters more than waiting for warning signs. When symptoms do show up, they typically include unusual vaginal discharge, or discharge from the penis that's white, cloudy or watery; a burning sensation when peeing; pain in the lower abdomen in women; bleeding between periods or after sex; and pain or swelling in the testicles in men.⁴ Left untreated, chlamydia can lead to pelvic inflammatory disease, infertility, ectopic pregnancy and reactive arthritis, so it's not an infection to sit on even though a course of antibiotics clears it.

Can you get rid of BV for good?

BV comes back in more than half of women within a year of treatment, and the full recurrence plan, including the 2025 partner trial and what the NHS offers after four episodes a year, is on why do I keep getting BV.⁵

Can chlamydia be mistaken for BV?

Yes, on symptoms alone. The NHS lists unusual vaginal discharge for both; chlamydia adds bleeding after sex or between periods, a burning feeling when you pee and pain in your lower tummy, and most people with chlamydia have no symptoms at all, so a discharge put down to BV can sit alongside an untested chlamydia infection.^{3, 4} BV is confirmed from an examination or a vaginal swab and chlamydia by its own urine or swab test, and the NHS says you can be tested even if you do not have any symptoms, so ask for both after a new partner or with any of those added symptoms.⁴

Can a chlamydia test be wrong?

Rarely, and in both directions. A false positive is usually leftover genetic material in the weeks after a course of antibiotics, or a handling error; a false negative is more often a test taken very soon after exposure, or a sample from a site that was not swabbed, which is why the NHS says a swab from your bottom, throat or eyes may be needed if those areas are affected.⁴ The NHS also says you may need to be tested again after treatment to check you no longer have chlamydia, and that if you are pregnant you are tested again 4 weeks after treatment; a result that does not add up is repeated, ideally on a different sample.⁴

Sources

1. Carter KA, et al. Epidemiologic evidence on the role of Lactobacillus iners in sexually transmitted infections and bacterial vaginosis. Sexually Transmitted Diseases, 2023. Systematic review and meta-analysis of sequencing studies; one author works for a live-culture manufacturer. PubMed 36729966.
2. Wiesenfeld HC, et al. Bacterial vaginosis is a strong predictor of Neisseria gonorrhoeae and Chlamydia trachomatis infection. Clinical Infectious Diseases, 2003. Cross-sectional study, 255 women. PubMed 12594649.
3. NHS. Bacterial vaginosis. Page last reviewed 19 June 2026. nhs.uk/conditions/bacterial-vaginosis.
4. NHS. Chlamydia. Page last reviewed 24 October 2024. nhs.uk/conditions/chlamydia.
5. Bradshaw CS, et al. High recurrence rates of bacterial vaginosis 12 months after oral metronidazole therapy. Journal of Infectious Diseases, 2006. Prospective cohort, 139 women, 12 months. PubMed 16652274.

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