Metronidazole for Bacterial Vaginosis: The First-Line Treatment
▶ In short — Metronidazole for BV
Metronidazole is the first-line treatment for bacterial vaginosis, recommended by NICE and BASHH. The usual course is 400mg twice a day for 5–7 days, which clears the infection in most women. It can be taken as tablets or applied as a vaginal gel (Zidoval). Avoid all alcohol during treatment and for 48 hours after.
Part of the Access Doctor Bacterial Vaginosis guide. For what BV is and its symptoms, see the understanding BV guide.
Why Metronidazole Is First-Line for BV
Bacterial vaginosis develops when the protective Lactobacillus bacteria in the vagina fall and anaerobic bacteria overgrow. Metronidazole is highly effective against exactly those anaerobic bacteria, which is why NICE and BASHH recommend it as the first-choice antibiotic for BV. It targets the overgrowth without wiping out everything, allowing the normal balance to re-establish.
New to this medicine in general? See what metronidazole is and how it works.
The Metronidazole Course for BV
| Option | Dose | Course |
|---|---|---|
| Standard course (preferred) | 400mg twice daily | 5–7 days |
| Single dose (alternative) | 2g once | One day — lower cure rate |
| Vaginal gel (Zidoval) | 0.75% gel, one applicator nightly | 5 nights |
The 5–7 day course is usually preferred over the single 2g dose because it clears BV more reliably. Whichever you're given, finish the whole course — stopping early makes recurrence more likely. For detailed dosing, timing and the alcohol rule, see how to take metronidazole.
No alcohol. Do not drink any alcohol while taking metronidazole (tablets or gel) or for 48 hours after your last dose — the combination causes an unpleasant disulfiram-like reaction.
Tablets vs Zidoval Gel
Both contain metronidazole and both are first-line; the choice comes down to preference.
| Oral tablets | Zidoval vaginal gel | |
|---|---|---|
| How used | Swallowed, twice daily | Applied into the vagina at night |
| Course | 5–7 days | 5 nights |
| Suits | Those who prefer tablets | Those who prefer to avoid oral antibiotics or get more nausea from tablets |
| Note | Systemic (whole-body) exposure | Mostly local; still avoid alcohol |
See the dedicated Zidoval gel guide, or compare all three BV medicines in BV treatment options.
Get Metronidazole for BV Online
Complete a free confidential consultation reviewed by GPhC-registered pharmacist independent prescribers. Discreet next-day delivery, no GP appointment needed.
Treat BV Online →How Quickly It Works & Cure Rate
Most women notice the discharge and fishy odour settling within 2–3 days of starting metronidazole, though the full course should still be completed. A correctly completed course clears BV in the majority of women (cure rates of around 70–80% at one month in studies).
2–3
days for symptoms to start improving
70–80%
cured at one month with the full course
50–70%
recurrence within a year
If BV Comes Back
BV recurring is common — around 50 to 70% of women have a recurrence within a year, and this does not mean the treatment failed. It reflects how hard it is to fully restore the protective vaginal bacteria. If you have three or more episodes in a year, speak to a clinician: options include a longer metronidazole course, suppressive vaginal gel, and addressing triggers (avoiding douching and scented products).
If Metronidazole Isn't Suitable
If you can't tolerate metronidazole — or it hasn't cleared the BV — the main alternative is Dalacin (clindamycin 2%) vaginal cream, applied nightly for 7 nights. Your prescriber will help you choose. Side effects of metronidazole are usually mild (metallic taste, nausea); the full list is in the metronidazole side effects guide.
How to Get Metronidazole for BV
Metronidazole is prescription-only in the UK, but you do not need a GP appointment. Through Access Doctor, complete a short confidential online consultation; a GPhC-registered pharmacist independent prescriber reviews it and, if BV treatment is appropriate, issues a prescription dispatched in discreet plain packaging — usually next working day.
Get assessed if you're pregnant or unsure. BV in pregnancy needs prompt, supervised treatment — Access Doctor's online BV service is not for use in pregnancy. If your symptoms are new, or include itching, soreness, pelvic pain or fever, get a clinical assessment, as this may point to a different condition.
Frequently Asked Questions
Is metronidazole the first-line treatment for BV?
Yes. NICE and BASHH recommend metronidazole as the first-line antibiotic for bacterial vaginosis. The usual course is 400mg twice a day for 5 to 7 days. It can be taken as tablets or applied as a vaginal gel (Zidoval).
What is the dose of metronidazole for BV?
The standard course is metronidazole 400mg twice a day for 5 to 7 days. A single 2g dose is an alternative but has a lower cure rate, so the 5–7 day course is usually preferred. The vaginal gel (Zidoval) is applied once nightly for 5 nights. Always finish the full course.
How quickly does metronidazole work for BV?
Most women notice the discharge and odour improving within 2 to 3 days. You should still complete the full 5–7 day course, as stopping early makes it more likely the BV will return.
Why does BV keep coming back after metronidazole?
BV recurs in around 50 to 70% of women within a year of treatment. This is because it is difficult to fully restore the protective vaginal bacteria, and biofilms can persist. Recurrence does not mean the treatment failed. If BV keeps returning, speak to a clinician about longer or suppressive options.
Can I take metronidazole for BV with alcohol?
No — avoid all alcohol during treatment and for 48 hours after your final dose. Combining them causes a disulfiram-like reaction with nausea, vomiting, flushing and palpitations. This applies to both the tablets and the vaginal gel.
References
- BASHH. UK National Guideline for the Management of Bacterial Vaginosis. 2023. bashh.org/guidelines
- NICE. Bacterial vaginosis: Clinical Knowledge Summary. 2023. cks.nice.org.uk/topics/bacterial-vaginosis
- Electronic Medicines Compendium. Metronidazole 400mg tablets: SmPC. 2024. medicines.org.uk/emc/product/981
- Electronic Medicines Compendium. Zidoval 7.5mg/g vaginal gel: SmPC. 2023. medicines.org.uk/emc/product/6148
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. Metronidazole is a prescription-only medicine — a medical consultation is required before it can be dispensed. If you are pregnant, or have itching, soreness, pelvic pain or fever, seek in-person assessment. In a medical emergency, call 999.