Bacterial Vaginosis (BV): UK Guide
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Bacterial Vaginosis (BV)
Bacterial vaginosis — symptoms, causes, diagnosis and treatment.
Key fact: Bacterial vaginosis (BV) is the most common vaginal condition in women of reproductive age in the UK. Up to half of all women with BV have no symptoms. It is not a sexually transmitted infection, not caused by poor hygiene, and straightforward to treat with the right prescription antibiotic.
What Is Bacterial Vaginosis?
Bacterial vaginosis is a condition caused by an overgrowth of certain bacteria in the vagina. The healthy vaginal microbiome is dominated by protective Lactobacillus species, which maintain an acidic pH (around 3.8–4.5) that keeps harmful bacteria in check. In BV, this balance is disrupted — lactobacilli decrease and anaerobic bacteria, particularly Gardnerella vaginalis, Prevotella and Mobiluncus species, overgrow. The result is a rise in vaginal pH and the production of amines that cause the characteristic fishy odour.
BV is not an infection in the traditional sense, not a sexually transmitted infection, and not caused by poor hygiene. It is a microbial imbalance that can develop in any woman of reproductive age — including those who have never been sexually active.
For a detailed comparison of BV with thrush and other vaginal conditions, see our Understanding BV guide.
Symptoms
Around half of all women with BV experience no symptoms. When symptoms do occur they are usually distinctive:
- Vaginal discharge — thin, watery and greyish-white or off-white
- Fishy odour — often more noticeable after sex or during menstruation when vaginal pH rises
- Mild itching or irritation around the vagina — less common; significant itch is more suggestive of thrush
- Burning on urination — occasional; if pronounced, also consider UTI
BV does not typically cause soreness, redness, swelling or pain during sex. These symptoms suggest an alternative or co-existing diagnosis and warrant clinical assessment.
Do not self-diagnose: The symptoms of BV overlap with those of thrush, trichomoniasis, and sexually transmitted infections. An accurate diagnosis is important before starting treatment.
Causes and Risk Factors
The exact mechanism that triggers the shift in vaginal microbiome is not fully understood. Certain factors consistently increase risk:
New or multiple sexual partners
Alters the vaginal bacterial environment. BV is more common in women who have female sexual partners.
Vaginal douching
Washing inside the vagina disrupts protective lactobacilli. The vagina is self-cleaning — internal washing is not recommended.
Perfumed soaps and washes
Scented products and vaginal deodorants used in the vaginal area can disrupt the natural bacterial balance.
Smoking
Independently associated with reduced vaginal lactobacilli and higher BV prevalence.
Hormonal changes
BV is more common at certain points in the menstrual cycle and in post-menopausal women. Oestrogen supports lactobacilli.
IUD use
Some studies suggest an increased risk of BV in women using copper IUDs, though evidence is mixed.
BV does not develop from toilet seats, swimming pools, shared towels, or casual contact. It is not a hygiene failure.
Diagnosis
BV is diagnosed clinically or via laboratory testing. The standard framework is the Amsel criteria — BV is confirmed when at least three of four criteria are met:
- Thin, homogeneous, white-grey vaginal discharge
- Vaginal pH greater than 4.5
- Positive amine (whiff) test — fishy odour on addition of potassium hydroxide
- Clue cells (vaginal epithelial cells coated in bacteria) on microscopy
In primary care and online consultation, diagnosis is typically made on the basis of reported symptoms, discharge characteristics and clinical history. A short online consultation with one of our GPhC-registered pharmacist independent prescribers can assess your symptoms and, where appropriate, issue a prescription without a GP appointment.
Treatment Options
BV is treated with antibiotics. NICE and BASHH 2023 recommend a stepped approach, with the choice of treatment depending on patient preference, pregnancy status, and any previous treatments.
| Treatment | Regimen | Route | First-line? |
|---|---|---|---|
| Metronidazole 400mg | Twice daily for 5–7 days | Oral tablets | Yes |
| Metronidazole 2g | Single dose | Oral tablets | Alternative (lower cure rate) |
| Zidoval (metronidazole 0.75% gel) | Once nightly for 5 nights | Vaginal | Yes (alternative to oral) |
| Dalacin (clindamycin 2% cream) | Once nightly for 7 nights | Vaginal | Second-line or patient preference |
Metronidazole and alcohol: avoid alcohol during treatment and for 48 hours after completing a course. Vaginal clindamycin (Dalacin cream) may damage latex condoms and diaphragms for up to 5 days after use. Male partners do not require treatment for BV.
Get BV Treatment Online
Access Doctor provides prescription BV treatment — metronidazole tablets, Zidoval gel and Dalacin cream — following a short consultation with our GPhC-registered pharmacist independent prescribers. No GP referral needed.
View BV Treatments →BV in Pregnancy
BV in pregnancy requires prompt treatment. Untreated BV in pregnancy is associated with:
- Preterm birth and premature rupture of membranes
- Low birth weight
- Postpartum endometritis
- Increased susceptibility to other infections
Metronidazole is the recommended treatment and is considered safe in pregnancy when prescribed by a qualified clinician. Do not self-treat during pregnancy — consult your GP or midwife. Access Doctor does not prescribe BV treatment for use during pregnancy through the online service.
Recurrent BV
Around 50 to 70% of women experience BV recurrence within one year of successful treatment. Recurrent BV (three or more confirmed episodes within 12 months) has a more complex management pathway. Options include extended metronidazole courses, suppressive vaginal metronidazole gel therapy, and specialist referral. See our guide on Dalacin Cream for BV Relief for more on recurrence management.
Prevention
BV cannot always be prevented, but these measures reduce risk and may help prevent recurrence:
- Avoid vaginal douching or washing inside the vagina
- Use unperfumed soaps and avoid scented feminine hygiene products
- Stop smoking
- Use condoms, particularly with new partners
- Wear breathable cotton underwear
- Shower rather than bathe where possible
When to Seek Help
See a clinician if:
- You have unusual vaginal discharge, odour or discomfort
- Symptoms do not improve within 3 days of starting treatment
- BV keeps recurring (three or more episodes in a year)
- You are pregnant
- You have a recent new sexual partner and are concerned about STIs
Urgent attention needed: Pelvic pain, fever, vomiting or pain during sex alongside vaginal discharge may indicate pelvic inflammatory disease (PID), which requires same-day assessment. Call your GP urgently or attend a sexual health clinic. In a medical emergency call 999.
BV & Treatment Guides
In-depth guides on BV and the medicines used to treat it:
Frequently Asked Questions
What is bacterial vaginosis?
Bacterial vaginosis (BV) is the most common vaginal condition in women of reproductive age. It is caused by an imbalance in the vaginal microbiome — normal protective lactobacilli decrease and other bacteria (particularly Gardnerella vaginalis) overgrow. BV is not a sexually transmitted infection, though sexual activity can alter the vaginal environment and increase risk.
What are the symptoms of BV?
The most distinctive symptom is an unusual vaginal discharge — typically thin, watery, greyish-white, and with a strong fishy odour that is often more noticeable after sex. Itching or irritation around the vagina is less common. Around half of women with BV have no symptoms at all.
Is BV an STI?
No. Bacterial vaginosis is not a sexually transmitted infection. It can develop in women who have never been sexually active. However, having a new sexual partner or multiple partners can alter the vaginal bacterial balance and increase risk.
How is BV treated?
BV is treated with antibiotics. NICE and BASHH recommend metronidazole as first-line treatment — either 400mg orally twice daily for 5 to 7 days, or 2g as a single dose. Alternatives include metronidazole 0.75% vaginal gel (Zidoval) for 5 nights, or clindamycin 2% vaginal cream (Dalacin) for 7 nights. All three are available on prescription through Access Doctor following a short online clinical assessment.
Does BV go away on its own?
BV sometimes resolves without treatment, but this cannot be relied upon. Untreated BV increases the risk of STIs and complications in pregnancy. Treatment is recommended for all symptomatic cases.
Why does BV keep coming back?
BV recurrence is common — approximately 50 to 70% of women experience a recurrence within a year of treatment. Recurrence is related to difficulty restoring the vaginal microbiome, continued risk factor exposure, and bacterial biofilm formation. Recurrent BV should be discussed with a clinician.
Can I treat BV during pregnancy?
BV in pregnancy requires prompt treatment due to risks including preterm birth. Metronidazole is considered safe when prescribed by a qualified clinician. Do not self-treat during pregnancy — consult your GP or midwife.
Speak to a UK Prescriber About BV
If you think you have bacterial vaginosis, a short online consultation with our GPhC-registered pharmacist independent prescribers can get you the right treatment quickly — without a GP appointment.
View BV Treatments →References
- British Association for Sexual Health and HIV (BASHH). UK National Guideline for the Management of Bacterial Vaginosis. BASHH, 2023. www.bashh.org/guidelines
- National Institute for Health and Care Excellence (NICE). Bacterial vaginosis: Clinical Knowledge Summary. 2023. cks.nice.org.uk/topics/bacterial-vaginosis
- NHS. Bacterial vaginosis. NHS.uk, 2023. nhs.uk/conditions/bacterial-vaginosis
- Bradshaw CS, Brotman RM. Making inroads into improving treatment of bacterial vaginosis — striving for long-term cure. BMC Infectious Diseases. 2015;15:292. PubMed: 26228675
- Electronic Medicines Compendium. Metronidazole 400mg tablets: Summary of Product Characteristics. 2024. medicines.org.uk/emc/product/981
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.
