References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Bacterial vaginosis (BV) is one of the most common causes of unusual vaginal discharge. It’s caused by an imbalance in the natural bacteria of the vagina rather than an STI. Lab testing for BV — often combined with tests for thrush and trichomoniasis — helps identify the cause of vaginitis so you get the right treatment.
Here’s what to know.
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What Is BV?
- An imbalance in the natural vaginal bacteria
- Lactobacilli are reduced; other bacteria overgrow
- Common, particularly in women with new partners or after antibiotics
- Not officially classed as an STI
Symptoms
- Thin, greyish-white discharge
- Fishy odour, often worse after sex
- Usually no itching
- Often no symptoms at all
How BV Is Tested
| Test | What It Shows |
|---|---|
| Vaginal pH | Higher than normal in BV |
| Microscopy (“clue cells”) | Specific bacterial pattern |
| NAAT | Identifies bacteria specific to BV |
| Amsel criteria | Combines findings to diagnose BV |
Treatment
- Metronidazole — oral tablets or vaginal gel
- Clindamycin — vaginal cream alternative
- Treatment usually 5-7 days
- Avoid alcohol with metronidazole
Recurrence
BV often recurs — up to half of women experience another episode within 12 months. Recurrence prevention strategies include:
- Avoiding douching
- Avoiding scented products internally
- Suppressive treatment for very frequent recurrences
- Treating female partners may help in some cases
Why It Matters
- BV is associated with increased HIV susceptibility
- Linked to preterm birth in pregnancy
- Can contribute to PID risk
- Affects quality of life
Combined Vaginitis Testing
Many vaginitis panels test for BV alongside thrush and trichomoniasis to identify the cause efficiently. This is more accurate than guessing based on symptoms alone.
Self-Care
- Avoid douching
- Use plain water for external washing
- Wear cotton underwear
- Avoid scented products
- Don’t use over-the-counter treatments without checking the cause
Read more: BV and HIV | Vaginitis tests | Vaginal infections
Frequently Asked Questions
Is BV an STI?
Not officially, but it’s associated with sexual activity.
Will it go away on its own?
Sometimes, but treatment is usually quicker and more reliable.
Should my partner be treated?
Male partners usually don’t need treatment. Female partners may benefit if BV keeps returning.
Related reading
- Can You Test for STIs While on Your Period?
- Common STI Symptoms in Women
- Does a Vaginal Yeast Infection Smell?
- HIV Risk from Vaginal Sex: What You Need to Know
- How Different STIs Affect Vaginal Discharge
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
