Q: What is bacterial vaginosis (BV)?

A: BV occurs when a healthy vaginal bacterial community changes so that there are more types of bacteria and a higher quantity of bacteria overall. This change usually causes a discharge and sometimes a strong odor.

Q: What causes bacterial vaginosis?

A: The short answer is that we don’t know.

However, BV seems to be associated with sex, though not as clearly as with a true sexually transmitted disease. Some women report having many episodes of BV when they are sexually active with one partner, but not with another partner. Others report getting BV over and over again during times when they aren’t having sex at all.

Q: How is bacterial vaginosis diagnosed?

A: The classic diagnosis for BV is based on four clinical findings:

  • A thin white or yellow discharge, often with an unpleasant or fishy smell
  • A fishy odor when potassium hydroxide is added to vaginal secretions
  • Vaginal secretions with a high pH level
  • The presence of “clue cells” (a particular vaginal bacteria that can be seen under a microscope)

Some providers use lab-based tests that look for enzymes made by the bacteria that cause BV. These enzyme tests work well. Some providers use a lab-based test that looks for Gardnerella vaginalis, a type of bacteria associated with BV. This type of test doesn’t work as well and is less efficient because 70-80% of healthy women have some Gardnerella in their vaginas. If this test is positive, you may or may not actually have BV.

Q: How is bacterial vaginosis treated?

A: There are two antibiotics that are recommended for the treatment of BV:

  • Metronidazole (such as Flagyl®, Metrogel®)
  • Clindamycin (Cleocin®, Clindesse®)

Each of these medications has an oral and a vaginal form—both types and both formulations have very similar success rates.

Q: How can I prevent bacterial vaginosis from returning?

A: Because we don’t know exactly what causes BV, it can be difficult to say exactly what will prevent it. However, there are a number of measures that may help:

  • Condom use: People who use condoms have a lower risk of BV. Although no one has studied whether starting to use condoms decreases recurrence, using condoms may help.
  • Hormonal birth control: People who use hormonal birth control (including pills, rings, injections or patches) have a lower risk of recurrent BV. Again, no one has studied whether starting these would help reduce recurrences, but we sometimes try this if hormones are a safe option for you.
  • Avoid douching: Douching can disrupt your healthy vaginal bacterial community and may increase the likelihood of BV coming back.
  • Longer-term antibiotics: If you’ve had three or more documented episodes of BV a year, using vaginal metronidazole twice a week for four months can decrease the chances of your BV returning.

Q: What about the other treatments I have heard about?

A: Possibly helpful for treating BV:

  • Vitamin C: One study1 of 142 European women evaluated vaginal use of silicone-coated 250mg vitamin C tablets to reduce BV recurrence and showed a nearly 50% decrease in recurrence of BV. A separate study2 used 250mg vaginal vitamin C to treat asymptomatic BV and showed an improvement in vaginal pH and Lactobacillus after 4 weeks. To help with BV prevention, 250 mg vitamin C should be used once daily vaginally for six days after your period. While silicone-coated vitamin C is not available in the US, enteric-coated vitamin C is available in the US and can be used in the same way.
  • Boric acid: Only one non-randomized study (in this type of study participants are not assigned to groups by chance and the investigation is not considered as rigorous as a randomized study), has reported using boric acid to try to eliminate bacteria that remain on the vaginal lining after treatment for BV. There haven’t been any more rigorous randomized trials of this treatment option, so it may or may not help. Overall boric acid is very safe, but should not be used during pregnancy. Note that boric acid should only be used vaginally. It is toxic if used orally—never take boric acid by mouth!
  • Probiotics: Several trials have examined probiotics for BV treatment, but these products are usually not adequate solutions. However, some people use them to prevent recurrence of BV. Multiple studies have evaluated this, and three have shown significant benefits from oral probiotics containing Lactobacillus rhamnosus GR. However, only one of those studies evaluated outcomes several months after stopping the probiotic – the others required that patients keep taking the probiotic every day. It is good to be cautious about probiotics—they are not regulated by the Food & Drug Administration, and some studies have shown that many products either do not contain the bacterial species described on the label or do not contain the amount listed. If you want to try a probiotic, pick one with Lactobacillus rhamnosus GR (such as Fem-Dophilus® or Rephresh ProB™, but we do not endorse any particular product).

Not helpful for treating BV:

  • Yogurt: There is very little data showing yogurt’s impact on BV. One study showed that a yogurt containing Lactobacillus acidophilus might help. Yogurt-soaked tampons definitely don’t work.
  • Douching: People report using vinegar, hydrogen peroxide and solutions with tea tree oil. While douching has been shown to decrease symptoms of BV, in most studies douching is also associated with an increased risk of BV recurrence, higher risk of sexually transmitted diseases and preterm delivery. We strongly advise against douching.
  • Vitamin D: Low levels of vitamin D in the blood have been associated with a higher risk of BV, but this does not seem to be a cause/effect relationship. There has been one randomized trial of vitamin D supplementation for prevention of BV recurrence (the study used 50,000 IU—many, many times the recommended daily vitamin D allowance of 600 IU!). This study showed an increase in blood levels of the vitamin, but showed no benefit for reducing BV.
  • Folic acid: There are no studies evaluating whether folic acid has any impact on BV.
  • Apple cider vinegar: Some people report that putting some apple cider vinegar in their bath water is helpful, which is perfectly safe. Other people make a drink with a tablespoon of vinegar in a glass of water, which is likely to be safe, if not very tasty. However, there have not been any clinical trials that examined the effectiveness of vinegar as a treatment for BV. Never douche with vinegar.

Read a piece featuring Caroline Mitchell, MD, MPH's research to learn more about the challenges of treating bacterial vaginosis.


  1. Krasnopolsky, et al. Efficacy of Vitamin C Vaginal Tablets as Prophylaxis for Recurrent Bacterial Vaginosis: A Randomised, Double-Blind, Placebo-controlled Clinical Trial, Journal of Clinical Medicine Research 2013
  2. Petersen E, et al.  Efficacy and Safety of Vitamin C Vaginal Tablets in the Treatment of Non-specific Vaginitis. A Randomised, Double blind, Placebo-controlled Study, European Journal Obstetric Gynecology and Reproductive Biology2004 117(1): pp70-75