Bacterial vaginosis (BV) assessment
An assessment to work out whether a change in vaginal discharge is caused by bacterial vaginosis, an imbalance of vaginal bacteria.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- BV is the most common cause of unusual vaginal discharge — typically thin, greyish-white with a fishy smell, usually without soreness or itching.
- It is an imbalance of vaginal bacteria, not an STI, though sex can trigger it; male partners are not usually treated.
- Often it can be recognised and treated without tests; confirming with a swab or pH check matters more in pregnancy, unclear cases, or when treatment fails.
- BV commonly comes back, sometimes within months, and can increase the risk of catching STIs, so an accurate assessment matters.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your specialist will give you advice for your situation.
Identifies the cause of unusual discharge so the right treatment is used
Self-diagnosing recurrent discharge as BV without an assessment, when an STI or another cause may be responsible.
A short examination and, sometimes, a swab or pH test. Mild discomfort only.
A clear explanation of whether it is BV, thrush or something else, and why.
A short examination and, sometimes, a swab or pH test. Mild discomfort only.
If typical BV is recognised, treatment can often be started straight away without waiting for lab results.
Laboratory results are usually available within days; the clinic will tell you how to get them.
Symptoms usually settle within a few days. Avoid triggers such as douches and perfumed products.
What is a bacterial vaginosis (BV) assessment?
Bacterial vaginosis (BV) is the most common cause of unusual vaginal discharge. It happens when the normal balance of bacteria in the vagina changes, with the usual protective bacteria (lactobacilli) reduced. The classic symptom is a thin, greyish-white discharge with a strong, fishy smell, often more noticeable after sex. BV does not usually cause soreness or itching, and about half of women with BV have no symptoms at all.
BV is not a sexually transmitted infection, although it can be triggered by sex and is more common with a new partner or change of partner. You cannot pass it to a male partner, and male partners are not usually treated.
Assessing BV means working out whether your symptoms are due to BV rather than thrush, an STI, or another cause. In many cases, a clinician can recognise typical BV from your symptoms and a simple examination and treat it without further tests. Confirming the diagnosis with tests is more important in pregnancy, when symptoms are unclear, or when treatment has not worked. Tests can include checking the vaginal pH (acidity) and a swab examined in the laboratory or under a microscope.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
BV vs thrush (common causes of discharge)
| BV | Thrush | |
|---|---|---|
| Discharge | Thin, greyish-white | Thick, white |
| Smell | Strong, fishy | Usually none |
| Itching/soreness | Not usual | Common |
| Cause | Bacterial imbalance | Yeast (Candida) |
Symptoms overlap and you can have both. An assessment helps tell them apart so the right treatment is used; do not assume which one you have.
Preparing for your test
- Avoid using vaginal douches, deodorants or perfumed products before your appointment, as these affect the assessment.
- If possible, do not have the appointment during your period, as blood can affect a pH test.
- Note your symptoms: the type of discharge, any smell, and whether there is soreness or itching.
- Mention if you are or might be pregnant, as this affects whether tests are needed and which treatment is used.
- Tell the clinician about a new sexual partner or change of partner, and any IUD (coil).
- Mention previous episodes and what treatment you have tried.
- Ask about STI testing if there is any chance of an STI, as symptoms can overlap.
What happens
At a GP or sexual health clinic, the clinician asks about your discharge and symptoms. Where appropriate, they examine the vulva and may use a speculum to look at the discharge and the cervix, to rule out other causes of an offensive discharge.
In many cases, typical BV can be recognised and treatment started the same visit without further tests. If the picture is unclear, if you are pregnant, or if previous treatment has not worked, they may test the vaginal pH and take a swab for the laboratory or microscopy.
If BV is diagnosed, you will usually be offered antibiotic treatment (tablets or a vaginal gel or cream) and advice on reducing things that can trigger it. Because symptoms overlap with STIs, you may be offered STI testing too.
Is this test right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- Self-diagnosing recurrent discharge as BV without an assessment, when an STI or another cause may be responsible.
- Treating presumed BV based on symptoms alone in pregnancy, where confirming the diagnosis matters more.
- Assuming BV when there is itching, soreness, sores or bleeding, which point to other causes.
- Relying on over-the-counter products without an assessment when symptoms persist or recur.
Delay or rearrange if…
- You are on your period, which can affect a pH test — the clinic may prefer to assess at another time.
- You have recently used douches or perfumed products that could affect the assessment.
- You have symptoms suggesting a different problem (sores, significant pain, abnormal bleeding) that need assessing first.
- You are unsure whether you are pregnant — confirm, as this affects testing and treatment.
Alternatives to discuss
- A symptom-based assessment without laboratory tests for typical BV.
- Testing for thrush or STIs if the cause of discharge is unclear.
- No treatment if there are no symptoms (treatment is generally for symptoms, not symptom-free findings).
- A maintenance or longer treatment plan for frequently recurring BV.
- Referral to a specialist sexual health clinic for persistent or recurrent problems.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Identifies the cause of unusual discharge so the right treatment is used
- Distinguishes BV from thrush and from STIs that need different treatment
- Allows prompt treatment, often at the same visit
- Is more thorough in pregnancy, where confirming the diagnosis matters more
- Usually offered alongside STI testing when symptoms could fit either
Risks & complications
- The mild discomfort of an examination or swab
- Diagnostic uncertainty, as symptoms overlap with thrush and STIs
- BV commonly coming back after treatment
- Treating based on symptoms alone occasionally being wrong
- A normal result despite ongoing symptoms, needing another look for the cause
- Needing a laboratory swab if the picture is unclear
- Missing a co-existing infection if STI testing is not done when it should be
- An incidental finding on examination that needs further assessment
- Persistent or frequently recurring BV that is difficult to control
The main limitation is that symptoms overlap with thrush and with STIs, so a positive 'fishy discharge' is not always BV. In pregnancy, when symptoms are unclear, or when treatment has not worked, confirming the diagnosis with a swab is more important. BV commonly recurs, so a single assessment may not be the end of the story.
Published figures to discuss
BV is a clinical assessment as much as a test, and symptoms overlap with thrush and STIs, so no single result is definitive. About half of women with BV have no symptoms, and BV commonly recurs after treatment. We describe these patterns in words rather than precise percentages, because reported recurrence and detection figures vary widely with the population, the diagnostic method and follow-up.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Symptoms recur after treatment | Common | BV often comes back, especially in the first few months; recurrence does not mean the diagnosis was necessarily wrong. | Guide sourcesClinical context |
| Misdiagnosis as thrush or an STI | Recognised overlap | Discharge and irritation overlap between BV, thrush, trichomoniasis, chlamydia, gonorrhoea and vulval skin conditions. | Guide sourcesClinical context |
| Pregnancy or post-procedure complications if infection is missed | Context-dependent | BV can matter more in pregnancy or before some gynaecological procedures, so symptoms should be assessed rather than repeatedly self-treated. | NHS — Bacterial vaginosisnhs.ukSource-linked context |
| Partner treatment given unnecessarily | Usually not recommended for male partners | BV is not classed as a typical STI; routine partner treatment is not usually helpful unless specialist guidance suggests otherwise. | Guide sourcesClinical context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is no physical recovery from the assessment. Afterwards, the focus is on treatment if BV is diagnosed, knowing that it can come back, and returning if symptoms persist or recur.
- Mild discomfort during an examination or swab that quickly passes
- Symptoms improving within days of starting treatment
- No lasting effects from the assessment itself
- The possibility of BV returning, sometimes within months
Aftercare
- If treated, take the full course of antibiotics or use the gel/cream exactly as directed.
- If using metronidazole tablets, avoid alcohol during treatment and for at least 24 hours after.
- Avoid vaginal douches, deodorants and perfumed bath products, which can trigger BV.
- Use plain water or an unperfumed wash for the external area only.
- Avoid getting shampoo or bubble bath in the genital area.
- Return if symptoms do not settle, change, or come back.
- Have STI testing if there is any chance of an STI, as symptoms overlap.
- In pregnancy, follow your maternity team's advice on treatment and follow-up.
- A note of your symptoms and any triggers you've noticed
- Avoiding douches and perfumed products before the appointment
- Any treatment collected and a plan to complete it
- A reminder to avoid alcohol if taking metronidazole tablets
- The clinic's contact details if symptoms persist or recur
- STI testing arranged if there is any chance of an STI
⚠ Get urgent help if…
- Lower tummy or pelvic pain, fever, or pain during sex (could suggest a different or deeper infection)
- Abnormal vaginal bleeding, especially after sex or between periods
- Symptoms that do not settle, or quickly return, after treatment
- In pregnancy: any vaginal bleeding, leaking fluid, severe pain, or signs of early labour
- Soreness, itching, blisters or sores, which point away from simple BV
- Feeling generally unwell with the discharge
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your specialist gives you.
Results & realistic expectations
A clear assessment tells you whether your symptoms are due to BV, and rules in or out other causes such as thrush or an STI. If BV is confirmed, treatment usually settles the symptoms within days.
Because symptoms overlap and about half of women with BV have no symptoms, the result is interpreted alongside your symptoms. A normal result when you still have symptoms means another cause should be looked for, rather than assuming nothing is wrong.
BV commonly comes back, sometimes within a few months, even after successful treatment. This does not mean the assessment was wrong. Avoiding triggers such as douching and perfumed products can help, and for frequent recurrences the clinic may suggest a longer course or a maintenance plan. An assessment reflects your situation at the time and may need repeating if symptoms return.
Related tests, treatments or support
A BV assessment is often combined with testing for thrush and for STIs, because the symptoms overlap and more than one can be present. In pregnancy, assessment and treatment are coordinated with your maternity team. If a coil (IUD) seems to be contributing to recurrent BV, this can be discussed.
Follow-up & long-term care
If treated for typical BV, routine follow-up is not always needed once symptoms settle. You should return if symptoms persist, change or recur, if you are pregnant and need monitoring, or if BV keeps coming back and a longer-term plan is needed. The clinic will follow up any swab or STI results taken.
- Avoid douching and perfumed vaginal products, which can trigger BV
- Use plain water or an unperfumed wash for the external area only
- Return promptly if symptoms recur, as recurrence is common
- Discuss a longer or maintenance treatment plan if BV keeps coming back
- Keep up cervical screening when invited, which is unaffected by having had BV
Repeat, follow-on and what comes next
- A normal result with ongoing symptoms means another cause should be looked for.
- BV commonly recurs, sometimes within months, and may need repeat or longer treatment.
- Frequent recurrences may need a maintenance plan rather than repeated single courses.
- If treatment has not worked, confirming the diagnosis with a swab is worthwhile.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- A clear explanation of whether it is BV, thrush or something else, and why.
- Treatment advice including completing the course and avoiding alcohol with metronidazole tablets.
- Practical advice on avoiding triggers to reduce recurrence.
- A clear route back to the clinic if symptoms persist or recur, with a maintenance plan for frequent recurrences.
- STI testing where appropriate, and coordinated care in pregnancy.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- Whether assessment is symptom-based or includes a pH test, swab or microscopy.
- Whether STI testing is done at the same time, if relevant.
- The consultation fee, if using a private service.
- The cost of any treatment (tablets, gel or cream), if obtained privately.
- Follow-up appointments if symptoms persist or BV recurs.
- Any extra assessment in pregnancy or for recurrent BV.
- Whether any tests (pH, swab, microscopy) are included or extra, if private
- Whether STI testing is included where symptoms overlap
- How results are given and how long they take
- The cost of treatment and follow-up
- What happens if symptoms persist or BV keeps coming back
- Whether pregnancy is taken into account where relevant
On the NHS? Assessment and treatment for BV are free on the NHS at GP practices and sexual health clinics; private assessment is available but the NHS route is free and widely accessible.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Being treated for BV without considering thrush or an STI when symptoms overlap.
- Not being told that BV commonly comes back.
- Not being told to avoid alcohol if metronidazole tablets are used.
- No advice on avoiding triggers such as douching and perfumed products.
- Not confirming the diagnosis with a swab in pregnancy or when treatment has failed.
Marketing red flags
- Selling 'BV cure' products that promise it will never return.
- Promoting routine douching or perfumed 'feminine hygiene' products, which can trigger BV.
- Treating discharge without assessing for STIs where relevant.
- Implying a single test can definitively rule BV in or out regardless of symptoms.
Choosing a specialist safely
- Check the specialist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good specialist will welcome every one of these.
- Are my symptoms more likely to be BV, thrush, or something else?
- Do I need a swab or pH test, or can this be treated based on my symptoms?
- Should I also be tested for STIs given my symptoms?
- What can I do to reduce the chance of BV coming back?
- If BV keeps recurring, is a longer or maintenance treatment an option?
- If I am pregnant, how does that change the assessment and treatment?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the specialist who carries out my test, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this test not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Is bacterial vaginosis an STI?
Do I always need a test to diagnose BV?
How is BV different from thrush?
How is BV treated?
Why does my BV keep coming back?
Can BV cause problems in pregnancy?
Does BV affect my risk of other infections?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: NHS — Bacterial vaginosis NICE CKS — Bacterial vaginosis NHS Scotland Right Decisions — Bacterial vaginosis West of Scotland sexual health network — Bacterial vaginosis guideline (2025)
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
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