Can BV Cause A Positive Chlamydia Test?

If you've just had a chlamydia test come back positive and you're also dealing with bacterial vaginosis (BV), it's natural to wonder whether the two are connected, or whether BV somehow tricked the test. The short answer: BV and chlamydia are two different infections, but they're more tangled up with each other than most people realise, and there are specific, documented reasons why a false positive can happen. Here's what's actually going on, based on the current clinical research and NHS guidance.

Can BV cause a false positive chlamydia test?

Yes, in some cases it can, though it's not the most common cause. Chlamydia tests (NAATs, or nucleic acid amplification tests) work by detecting genetic material from the bacteria Chlamydia trachomatis in a urine or swab sample. Bacterial vaginosis throws the vagina's bacterial balance off, and that shift can occasionally interfere with how a sample reacts in the lab. Certain bacteria associated with an unbalanced vaginal microbiome, such as Mycoplasma or Ureaplasma species, can cross-react with some test kits and produce a result that looks positive when chlamydia isn't actually present.

Other things that can cause a false positive alongside or instead of BV include:

• Lab handling errors or a contaminated sample
• Leftover bacterial DNA from a chlamydia infection you were recently treated for (the test can pick up fragments even after the infection has cleared)
• Testing too soon after finishing antibiotics
• Not following the self-test kit instructions correctly

If you think your result doesn't add up, the standard advice from sexual health clinics is to ask for a repeat test, ideally using a different sample type or method, before starting to worry unnecessarily.

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

This is where it gets more interesting than a simple lab mix-up. Research has increasingly shown that BV and chlamydia are genuinely connected, just not in the way people often assume.

A 2003 study published via the NIH found that bacterial vaginosis was a strong predictor of both gonorrhoea and chlamydia in women who'd recently been exposed to a partner with urethritis. More recently, a 2025 study out of Albert Einstein College of Medicine, Roswell Park Comprehensive Cancer Center and the Icahn School of Medicine at Mount Sinai went further: researchers sequenced vaginal and cervical samples from over 560 women and discovered that BV isn't one single condition. There are at least two distinct subtypes, and one of them specifically raises the risk of picking up chlamydia. The theory is that this subtype changes the cervicovaginal environment in a way that makes it easier for chlamydia to take hold.

That doesn't mean BV causes chlamydia directly. BV is an overgrowth of the bacteria already living in your vagina, most often triggered by things like a new sexual partner, douching, perfumed products, or an IUD, 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 shows is that BV weakens your natural defences (partly by making the vagina less acidic) and disrupts the protective lactobacilli that normally keep harmful bacteria in check. That leaves you more vulnerable to catching an STI like chlamydia if you're exposed to it, not that BV magically converts into one.

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.

Here's a quick 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, roughly 70% of women and a large share of men, 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. That's the only way to know for certain which one (or both) you're dealing with. We've unpacked this confusion in more depth in Can BV mean STD? if you'd like the fuller picture.

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

No. BV cannot transform into chlamydia, no matter how long it goes untreated. They're caused by entirely different organisms, and one doesn't evolve into the other. What untreated BV does do is raise your risk of picking up chlamydia (or gonorrhoea, HIV or HPV) if you're exposed to them, because of the way it disrupts your natural bacterial defences. So if you have BV and you're not sexually active, there's no route for it to "become" an STI. If you are sexually active while you have BV, especially without a condom, your odds of picking up an STI go up. That's the real mechanism, not transformation, but increased susceptibility.

Left untreated, BV itself can also lead to its own complications, particularly in pregnancy, where it carries a small increased risk of premature birth or miscarriage. That's a good enough reason on its own to get it treated rather than waiting to see if it clears up. 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 (metronidazole is the most commonly prescribed), while chlamydia requires its own course of antibiotics, sometimes a single dose, sometimes a 7 to 14 day course. Having both at once just means you'll need both treatment courses, and you'll usually be advised to avoid sex until you and any partner have finished treatment and tested clear.

What can make you falsely test positive for chlamydia, besides BV?

BV is one possible factor, but it's far from the only one. Other documented causes of a false positive include:

• A urinary tract infection (UTI): bacteria like E. coli can occasionally interfere with test accuracy, and inflammation from a UTI can also affect results.
• Recent treatment: if you had chlamydia and were successfully treated, leftover bacterial DNA can sometimes still be picked up by sensitive NAAT tests for a short period afterwards.
• Sample contamination: improper collection, or contamination during lab processing, is one of the more common practical causes.
• Cross-reacting bacteria: certain other bacterial infections can occasionally trigger a reactive result.

Genuine false positives are still relatively uncommon. Chlamydia tests are more prone to false negatives than false positives; some studies put the false negative rate as high as 28% in women and up to 8% in men, depending on the test type and how it's used. In other words, if anything, chlamydia is more likely to go undetected than to be wrongly flagged, so a positive result should still be taken seriously rather than dismissed.

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

This comes up a lot, and it isn't proof that someone's been unfaithful. There are several genuine explanations:

• Timing: chlamydia can take one to several months to become detectable, so a partner tested at a different point in the infection's timeline might get a different result.
• Sensitivity differences: not all tests are equally accurate, and a low bacterial load can be missed.
• Site of infection: chlamydia can 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: this is possible too, but it's one of several explanations, not the default assumption.

If this situation comes up, 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 (the majority) 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:

1. Unusual vaginal discharge, or discharge from the penis that's white, cloudy or watery
2. A burning sensation when peeing
3. Pain in the lower abdomen (in women)
4. Bleeding between periods or after sex
5. Pain or swelling in the testicles (in men)

Left untreated, chlamydia can lead to pelvic inflammatory disease, infertility, ectopic pregnancy, and joint pain (reactive arthritis), so it's not an infection to sit on even though it's easily cured with antibiotics.

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, GPs can test for BV, and free NHS chlamydia self-test kits are available through pharmacies and sexual health clinics, with free postal kits specifically for under-25s. Boots and other high street pharmacies also sell chlamydia 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.

Can you get rid of BV for good?

BV is very treatable, but it's also one of the more stubborn conditions to keep away long-term. It's common for it to return within a few months of treatment, and if you get it more than four times a year, a longer course of antibiotic gel may be recommended to break the cycle. Simple habits help too: washing with water and plain unperfumed soap, avoiding douches, vaginal washes and deodorants, showering rather than bathing, and steering clear of strong detergents on your underwear. None of these guarantee BV won't come back, but they reduce the chances and support the vagina's natural bacterial balance, which is ultimately what keeps both BV and your susceptibility to infections like chlamydia in check.

If you're dealing with recurring BV, or you're not sure whether what you're experiencing is BV, an STI, or both, don't try to guess from symptoms alone. Get tested. It's the only way to know what you're actually treating.

If you'd like more on this subject, our Health Insider blog covers bacterial vaginosis in more depth, from causes and prevention to treatment options. And if you've got a specific question, you can always send us a message on Instagram.