Bacterial vaginosis (BV) is a very common, treatable change in the vagina’s natural bacterial balance — not a sign of poor hygiene, and often not caused by anything you’ve done “wrong.” It’s usually straightforward to treat, though it can come back, and there are now evidence-based ways to reduce that risk.
What is BV?
Your vagina naturally hosts a community of bacteria, usually dominated by protective species called lactobacilli. BV happens when that balance shifts away from lactobacilli towards a wider mix of other bacteria (including Gardnerella vaginalis and several others). This changes the vagina’s chemistry — raising its pH and producing the compounds behind the odour some people notice.
BV is extremely common — estimates range from around 1 in 4 to almost 1 in 3 people with a vagina of reproductive age globally, though rates vary a lot between populations.
There’s a strong body of evidence linking how BV is acquired to sexual activity — including a younger age at first sex, more sexual partners, a new partner, and not using condoms. Partners with a penis can carry BV-associated bacteria on the penile skin and in the urethra, and couples where both people have a vagina show very high rates of sharing the same bacteria. This is why some guidelines now describe BV as having features of a sexually transmissible infection, even though it’s not classified as an STI in the traditional sense.
Symptoms — and why you might have none at all
If BV does cause symptoms, the most common are:
- A thin, white or greyish vaginal discharge
- A noticeable vaginal odour, sometimes described as fishy
Up to half of people with BV have no symptoms at all, so it’s often picked up incidentally during another check-up or swab.
Why it’s worth treating
BV itself isn’t dangerous, but it is worth taking seriously, particularly if you’re symptomatic, pregnant, or about to have a gynaecological procedure. BV has been associated with a higher chance of:
- Pregnancy complications, including miscarriage, premature labour, and infection of the membranes around the baby
- Pelvic inflammatory disease (PID), particularly after procedures like an IUD insertion or a surgical termination of pregnancy
- Acquiring other infections, including chlamydia, gonorrhoea, herpes, and HIV — BV appears to roughly double to quadruple this risk
This is one of the reasons your doctor may want to treat BV even if it isn’t bothering you much, especially around a planned procedure.
How BV is diagnosed
BV can’t reliably be self-diagnosed, because its symptoms can overlap with other common causes of discharge, like thrush. Your doctor will usually take a vaginal swab and look for a combination of clues: the appearance of the discharge, the vaginal pH, a characteristic odour when a testing solution is added, and “clue cells” seen under the microscope. Some clinics also use a molecular (DNA-based) swab test.
The evidence doesn’t currently support routinely testing for BV before a low-risk IUD insertion or termination of pregnancy if you have no symptoms — but it’s reasonable to mention any BV history or symptoms beforehand so it can be tested for and treated first if needed.
Treating BV
BV is treated with a course of antibiotics — either metronidazole tablets taken twice daily for about a week, or an antibiotic cream or gel (metronidazole or clindamycin) used inside the vagina for five to seven nights. A single large “stat” dose of antibiotic is also an option in some cases, but is linked with a higher chance of BV returning, so a full course is generally preferred.
A few practical notes: metronidazole tablets can cause nausea, so take them with food, and avoid alcohol during treatment and for 48 hours after finishing. Vaginal creams and gels can weaken latex condoms, so factor that in if you’re relying on them. Treatment during pregnancy uses the same medicines and is considered safe if you have symptoms.
Douching or other intravaginal “cleaning” products aren’t recommended — they can disrupt the vaginal bacteria further and are linked with an increased risk of BV. There currently isn’t enough evidence to recommend vaginal probiotics or lactic acid products for treating BV, although this is an active area of research.
Sexual partners and BV
This is a genuinely new part of BV care. A 2025 randomised controlled trial found that when an ongoing male partner is treated with a week of oral antibiotics plus an antibiotic cream applied to the penile skin, at the same time his partner is treated for BV, cure rates improve substantially over the following 12 weeks. This suggests that reinfection from an untreated partner is a significant reason BV keeps coming back.
If your partner has a penis
Concurrent partner treatment can now be offered: 7 days of oral metronidazole for your partner, combined with a clindamycin cream applied to the penile skin twice daily for 7 days. Both of you would take your treatments at the same time, avoid unprotected sex until you’ve both finished, and use condoms consistently in the meantime (though the creams involved can weaken latex).
If your partner has a vagina
There haven’t yet been clinical trials of partner treatment in relationships where both partners have a vagina, but studies consistently find very high rates of shared BV-related bacteria within these partnerships. Current advice is to offer testing to a female partner so that BV can be found and treated if present, ideally around the same time. Research into whether treating both partners improves cure rates in this group is ongoing.
If you have more than one ongoing partner, treating everyone around the same time gives the best chance of avoiding reinfection from someone who hasn’t been treated yet.
Why BV can come back
BV recurrence is common — more than half of people experience it again within 3 to 12 months of treatment. Recurrence has been linked to having an ongoing sexual partner and not using condoms, which is consistent with reinfection playing a large role.
If BV keeps coming back, your doctor might suggest a longer course of vaginal metronidazole gel (used twice weekly for around 4 months), alongside partner treatment where relevant. Vaginal boric acid is sometimes used for hard-to-treat recurrent BV, but this needs specialist guidance and hasn’t shown lasting benefit once stopped.
A note for IUD users
Copper IUDs are associated with a higher chance of developing and of BV coming back (the link with hormonal IUDs is less clear). If you develop BV with a copper IUD in place, it’s treated the same way — you don’t need to have it removed. But if BV keeps recurring, it’s worth discussing with your doctor whether switching methods, or removing and reinserting after treatment, makes sense for you.
When to see your doctor again
- Your symptoms don’t settle after treatment, or come back soon after
- You’re pregnant and have symptoms of BV
- You have recurrent BV (three or more episodes in a year) and want to explore longer-term options
- You have an ongoing partner and would like to discuss partner treatment
A “test of cure” isn’t usually needed if your symptoms go away — but if they persist or return, it’s worth being retested rather than assuming it’s the same thing recurring, since other infections can look similar and sometimes occur alongside BV.
Key takeaways
- BV is a very common shift in the vagina’s natural bacterial balance — not a hygiene problem, and nothing to feel embarrassed about.
- Around half of people with BV have no symptoms; when they occur, the main ones are discharge and odour.
- It’s treated with a short course of antibiotic tablets or vaginal cream/gel — avoid alcohol with metronidazole tablets, and avoid douching.
- BV comes back for many people, often linked to an untreated ongoing partner — treating partners at the same time is now a recommended option that improves cure rates.
- See your doctor again if symptoms don’t clear, keep returning, or you’re pregnant.
