How Long Does it Take for Metronidazole to Work?
Metronidazole is the first-line treatment for bacterial vaginosis (BV). It is an antibiotic that works by killing the bacteria responsible for the infection and is available as oral tablets and a vaginal gel. Metronidazole can be up to 90% effective at clearing bacterial vaginosis.
Despite its effectiveness, the big question is, how long does it take for metronidazole to work for bacterial vaginosis? Here, we’ll explore how long before you’ll get relief from BV, why you should finish the course, and give you some self-care tips if you currently have the condition.
What Does Metronidazole Do?
Metronidazole is a type of antibiotic that is used to treat several infections in the body. It works by killing the bacteria causing the infection by diffusing into the organism, interacting with its DNA to stop the synthesis of proteins crucial for its survival, causing the DNA to break, and ultimately resulting in the bacteria's death.
Some research also shows that in recurrent BV, metronidazole can temporarily reinstate a healthy vaginal microbiome (good bacteria). It’s thought to promote healthy bacteria types by depleting the bad ones, which cause BV.
How Quickly Does Metronidazole Work?
When you take metronidazole tablets, they start working almost immediately. Because the body absorbs it so well, metronidazole reaches its peak concentration in the blood within two hours. Most people who take metronidazole will notice an improvement in their symptoms within a few days, but it can take longer.
When compared to dequalinium chloride vaginal tablets, oral metronidazole tablets were found to be more effective in curing BV in 7 days, with a cure rate of 93.2%, compared to 92.8% in those given dequalinium chloride for 6 days. Therefore, most people will be BV-free within one week.
How Long Does a Single Dose of Metronidazole Take to Work for BV?
In some cases, you may be given a single dose of 2g of metronidazole oral tablets. This is usually prescribed when sticking to the usual 5- to 7-day course is challenging. Clinical trial data show that a single 2g dose resolved BV symptoms within 7 to 10 days in 86% of people compared to 97% treated with a 7-day course.
Why is it Important to Complete Your Course of Metronidazole?
It is essential to complete the course of metronidazole prescribed by your clinician, even if you are feeling better. That’s because the infection could recur if you stop your treatment prematurely. If you finish treatment early, a small number of bacteria may remain in the body. Without antibiotics, these bacteria can continue to grow and cause the infection to recur.
Frequently Asked Questions
If you’re one of the 23 to 29% of people affected by bacterial vaginosis and have been given the first-line therapy, metronidazole, you’re probably wondering, “How long does it take for metronidazole to work?” Here, we answer some of the most common questions about metronidazole for BV, including how to tell if it's working and what to do if you’re pregnant.
Metronidazole
- Short course of treatment
- Effectively reduces the infection
- Same-day dispatch from a UK pharmacy
How Long Does BV Take to Go Away?
With antibiotic treatment, like oral metronidazole tablets, it can take 5 to 7 days to clear the infection from your system. However, recurrent bacterial vaginosis is common, with some research showing that recurrence rates can be as high as 69% within 12 months of antibiotic treatment. If BV comes back, you’ll need a further course of antibiotics.
Even if you feel well before your treatment ends, it is essential to complete the entire course of antibiotics you have been prescribed to minimise the chance of the infection returning.
How Long Does Metronidazole Stay in Your System?
The elimination half-life of metronidazole is 8 hours. That is the time it takes for half of the therapeutic dose to be eliminated from your system. It will take around 44 hours for metronidazole to completely leave your body. However, if you have liver issues, it can take longer.
Because it can take 44 hours to clear from your body, it is recommended that you avoid drinking alcohol for 2 days after your last metronidazole dose, to limit the chance of a severe reaction. Find out more in our metronidazole and alcohol expert guide.
How Do I Know if Metronidazole is Working?
Most people notice an improvement in their BV symptoms after a few days of starting metronidazole. Often, this is a convincing sign that metronidazole is working. However, it can take up to 7 days to feel the full effects, so it is essential to complete your course.
You may also experience some side effects when taking oral metronidazole tablets, like nausea, vomiting, diarrhoea, or a metallic taste in your mouth. However, these should not be used as signs that the infection is clearing. If your side effects are severe or causing you concern, speak to your clinician for advice.
What if Metronidazole Doesn’t Work for BV?
Metronidazole may not be effective or suitable for everyone. If that’s the case, your clinician may prescribe an alternative medication, such as clindamycin, or recommend a different form of metronidazole, like a vaginal gel.
At Prescription Doctor, we can provide the following alternatives for BV:
- Dalacin cream: A vaginal cream that contains the antibiotic clindamycin. It is applied directly inside the vagina for 7 nights, and research shows that clindamycin is over 90% effective at clearing BV.
- Zidoval: A vaginal gel that contains 0.75% metronidazole. Because it is applied inside the vagina and acts locally, it is less likely to cause side effects compared to oral metronidazole tablets.
Is Metronidazole Safe While Pregnant?
Yes, metronidazole is generally considered safe and effective during pregnancy. However, it should only be taken if necessary and under the guidance of a doctor. Pregnant women will not be given a single dose of oral metronidazole tablets.
Although it may be suitable to take metronidazole during pregnancy, you should discuss your individual circumstances with your clinician. You can find out more in our dedicated guide: 'Can I take metronidazole when pregnant?'
Where Can I Buy Metronidazole?
The usual treatment for bacterial vaginosis is metronidazole. You can buy Metronidazole online from Prescription Doctor with a private prescription.
To request metronidazole from our clinicians, you will need to:
- Fill out a short online medical questionnaire. The answers you provide will enable our clinicians to assess whether metronidazole is an appropriate treatment for bacterial vaginosis for you.
- If your order is approved by 3pm on a weekday, our UK-registered pharmacy will dispatch your medication the same day via a next-day service.
- If your order isn’t approved, you’ll receive a full refund. If our clinician doesn’t think metronidazole is suitable for you, you will receive a full refund as part of Prescription Doctor’s money-back guarantee.
Metronidazole
- Short course of treatment
- Effectively reduces the infection
- Same-day dispatch from a UK pharmacy
Treat BV Fast With Metronidazole From Prescription Doctor
Bacterial vaginosis is a common condition, and for 50% of women who experience symptoms, they can be uncomfortable and debilitating. Therefore, receiving fast and effective treatment is crucial to help you return to your normal self.
At Prescription Doctor, we understand the importance of accessing hassle-free treatment from a trusted and fully regulated service. That’s why you can order your bacterial vaginosis treatment directly from us, without the need for a face-to-face appointment. We're also proud to provide a holistic support service for people dealing with BV, answering questions such as ‘how long does it take for Metronidazole to work?’, while providing tips on how to prevent BV and explaining why the condition may keep coming back.
Start your BV consultation now to get access to effective treatment today.
Sources
- BMC Women's Health (2023): Impact of (recurrent) bacterial vaginosis on quality of life and the need for accessible alternative treatments.
- Drugs.com (2024): How long does it take metronidazole to leave your system?
- Human Microbiome Journal (2021): The effect of oral Metronidazole on the vaginal microbiome of patients with recurrent bacterial vaginosis: A pilot investigational study.
- JAMA (2024): Efficacy of Dequalinium Chloride vs Metronidazole for the Treatment of Bacterial Vaginosis.
- NICE (2023): Bacterial vaginosis: How common is it?
- NIH (2025): Bacterial vaginosis: Learn More – Which treatments are effective in bacterial vaginosis?
- NIH (2023): Metronidazole.
- NHS (2022): Bacterial vaginosis.
- Pfizer: Metronidazole Tablets.
- PubMed (2020): Impact of oral metronidazole treatment on the vaginal microbiota and correlates of treatment failure.
- PubMed (1985): Comparison of single-dose vs one-week course of metronidazole for symptomatic bacterial vaginosis.
Authored By
Leanne Edermaniger
Medical Content WriterPublished on: 11/08/2023 Re-Published on: 17/09/2025
Reviewed By
Mohamed Imran Lakhi
MPharm - Lead PharmacistReviewed on: 17/09/2025
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