Using Metronidazole to Treat Bacterial Vaginosis

Bacterial vaginosis (BV) is a common bacterial vaginal infection affecting roughly 30% of women ages 14 to 49 in the United States. This infection occurs when bad bacteria outweigh good bacteria in the vagina. 

84% of women with BV do not have symptoms. When symptoms are present, the most common is a strong “fishy” vaginal odor and an increase in vaginal discharge.

Metronidazole (such as the brand Flagyl) is an antibiotic used to treat bacterial vaginosis. This article reviews the basics of metronidazole, dosage, side effects, effectiveness, other medications for BV, and more. 

woman taking metronidazole for bacterial vaginosis

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Metronidazole for Bacterial Vaginosis

Metronidazole is considered the first line of treatment for BV. This means it’s one of the preferred antibiotics used to treat BV. 

Metronidazole is the generic version. Brand names include: 

  • Flagyl
  • Protostat
  • MetroCream 
  • MetroGel 
  • Noritate
  • Vandazole
  • Nuvessa
  • Pylera

Metronidazole comes in capsules, tablets (pills), creams, gels, and intravenous (IV) forms. It can be given orally (by mouth), vaginally, or intravenously. Prescriptions to treat BV are typically for oral or vaginal administration. 

Is Metronidazole Safe If You're Pregnant or Breastfeeding?

Both oral and vaginal metronidazole are safe to take while pregnant and breastfeeding. However, healthcare providers often prefer vaginal cream since the medication does not distribute throughout the body as much as it does with oral medication. 


The following are typical dosages for metronidazole when treating BV:

  • Oral dose: 500 milligrams (mg) twice daily for seven days
  • Intravaginal dose: 0.75% gel, one applicator intravaginally for five nights

Sometimes, healthcare providers will prescribe oral and vaginal medications for you to take simultaneously. They might also increase the dose or time you take the medication, especially if the infection returns after initial treatment.

Why It's Important to Take All of Your Prescribed Antibiotics

When your healthcare provider prescribes metronidazole or another antibiotic, it’s important to take all the medication, even if the symptoms cease. Stopping antibiotics too early can cause the infection to return and for you to build resistance to the antibiotic. 

Side Effects

Common side effects of metronidazole include:

  • Nausea and vomiting
  • Abdominal pain
  • Metallic taste

Less common side effects include:

Food Decreases the Risk of Nausea, Vomiting, or Abdominal Pain

Taking metronidazole with food helps decrease the risk of stomach upset, including nausea, vomiting, and abdominal pain. Stomach upset is less common with vaginal metronidazole compared to oral administration.


Metronidazole can interact with the following medications:

  • Coumadin, Jantoven (warfarin)
  • Lithobid, Eskalith (lithium)
  • Clindacin, Cleocin, Clindesse (clindamycin)
  • Some anti-seizure medications

Vaginal metronidazole can increase your chance of getting a yeast infection. Your provider may prescribe Diflucan (fluconazole) by mouth or probiotics to decrease this risk, especially with extended treatment. 

Metronidazole vaginal cream can weaken birth control methods such as latex condoms and diaphragms. It’s best to use another form of birth control during treatment and for five days after treatment is complete.


Some studies show a cure rate of over 90% after one week of treatment and 70% to 80% after four weeks.

There is some concern that metronidazole alone may temporarily balance the bacteria in the vagina, but the risk of recurrence is high. Adding probiotics along with antibiotics is becoming a more common practice. Probiotics can help with a more permanent or long-term solution to balancing the vaginal flora (microorganisms).

Who Should Avoid Taking Metronidazole

The following people should avoid taking metronidazole:

  • Those taking Antabuse (disulfiram): Avoid metronidazole if you have taken Antabuse (disulfiram) within two weeks. This medication is for alcohol use disorders and could cause a psychotic reaction if given metronidazole.
  • Those allergic to nitroimidazole medications: This includes Flagyl (metronidazole), Tindamax, Fasigyn, Simplotan (tinidazole) and Solosec (secnidazole).
  • Those who drink alcohol: While some in the medical community contest this, the manufacturer recommends avoiding alcohol while taking metronidazole and for at least three days after the last dose. Drinking alcohol with metronidazole can cause stomach cramps, nausea, vomiting, headaches, and flushing.

Other Bacterial Vaginosis Medications

One of the following antibiotics may also be used to treat BV: 

  • Clindam, Cleocin, Clindesse (clindamycin): 300 mg twice daily for seven days, taken orally
  • Clindam, Cleocin, Clindesse (clindamycin): 100 mg each night for three nights, intravaginally
  • Tindamax, Fasigyn, Simplotan (tinidazole): 2 grams per day for two days or 1 gram per day for five days, taken orally
  • Solosec (secnidazole): 2 grams in a single dose, taken orally

While not as common, Xifaxan (rifaximin) may also be prescribed for BV. 

Alternative Treatment Options

Your healthcare provider may also consider the following alternative treatments, either alone or with antibiotic treatment:


Recurring (returning) infections are common after treatment of BV. In fact, 50% of women get another infection within 12 months of treatment. BV is considered recurring when a woman has at least three infections in one year. 

If you have a recurring infection, your healthcare provider may increase the dose and time you take antibiotics. Sometimes, they prescribe a maintenance dose of vaginal cream to help prevent a recurrence.

It’s best to avoid sexual contact until treatment has ended and your symptoms have resolved. If your intimate partner is a woman, they should seek treatment as BV can spread between female sex partners. However, if your intimate partner is male, research does not indicate that they need treatment.

Prevention of BV

The following guidelines can prevent or reduce the risk of bacterial vaginosis:

  • Avoid douching
  • Quit smoking.
  • Avoid highly fragranced soaps, detergents, sprays, or feminine hygiene products.
  • Wear underwear made with a breathable fabric, such as cotton.
  • Wipe from front to back after you use the bathroom.
  • Avoid intrauterine devices (IUDs) if you have a recurrent BV infection.
  • Use condoms for sexual intercourse and dental dams for oral sex.
  • Avoid flavored condoms or lubricants.
  • Limit the number of sexual partners or abstain from sexual intercourse.
  • Avoid vaginal contact with anything that has touched your anus.
  • Clean sex toys after every use.


Bacterial vaginosis (BV) is a common bacterial vaginal infection that occurs when bad bacteria outweigh good bacteria in the vagina. Metronidazole is an antibiotic used to treat BV. It can be given orally (by mouth) or intravaginally (inserted into the vagina). The most common side effects are stomach upset. 

Metronidazole is highly effective, but the chances of the infection recurring are high. In this case, healthcare providers may prescribe higher doses for longer, both vaginal and oral medication together, and probiotics to prevent a recurrence. 

Alternative antibiotics and other treatments, such as boric acid, vaginal vitamin C, or sucrose gel, may also be suggested. 

A Word From Verywell

Having bacterial vaginosis can be inconvenient, frustrating, and embarrassing. It can occur and reoccur even when you have been trying your best to prevent it. Finish the entire metronidazole prescription for BV. Not taking all of it can increase your chance of recurrence or resistance to the antibiotic.

Frequently Asked Questions

  • How long does it take for metronidazole to work for BV?

    Symptoms usually start to resolve after taking metronidazole for a few days. For some, it can take a couple of weeks. It’s important to take all antibiotics even if the symptoms are gone. Not taking all of them increases your risk of resistance to the antibiotic and a recurrence (return) of the infection.

  • How much metronidazole do I take for BV?

    When metronidazole is prescribed orally (by mouth), the initial treatment is usually 500 mg twice daily for seven days. The intravaginal dose is typically 0.75% gel, with one applicator for five nights. Sometimes healthcare providers will prescribe both oral and vaginal medication or increase the dose and time you take the medication. This is especially true if the infection returns after initial treatment.

  • Can BV go away without treatment?

    Yes, sometimes BV resolves on its own. Some women don’t realize they have BV because they never have symptoms. For others, symptoms may come and go. It’s best to seek treatment any time you have symptoms. This helps decrease your risk of getting sexually transmitted infections (STIs) or other complications of BV.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Bacterial vaginosis (bv) statistics.

  2. Bagnall P, Rizzolo D. Bacterial vaginosis: a practical review. J Am Acad Phys Assist. 2017; 30(12):15-21. doi:10.1097/01.JAA.0000526770.60197.fa

  3. UpToDate. Bacterial vaginosis: treatment.

  4. Planned Parenthood. What is bacterial vaginosis?

  5. U.S. Food and Drug Administration. Flagyl (metronidazole).

  6. Wang Z, He Y, Zheng Y. Probiotics for the treatment of bacterial vaginosis: a meta-analysis. Int J Environ Res Public Health. 2019;16(20):3859. doi:10.3390/ijerph16203859

  7. Goje O, Shay E, Markwei M, et al. The effect of oral metronidazole on the vaginal microbiome of patients with recurrent bacterial vaginosis: a pilot investigational study. Human Microbiome Journal. 2021;20. doi: 10.1016/j.humic.2021.100081

  8. Centers for Disease Control and Prevention. Std facts - bacterial vaginosis.

Additional Reading

By Brandi Jones, MSN-ED RN-BC
Brandi is a nurse and the owner of Brandi Jones LLC. She specializes in health and wellness writing including blogs, articles, and education.