Merck Manual

Please confirm that you are not located inside the Russian Federation


Bacterial Vaginosis (BV)


Oluwatosin Goje

, MD, MSCR, Cleveland Clinic, Lerner College of Medicine of Case Western Reserve University

Last full review/revision Sep 2019| Content last modified Sep 2019
Click here for the Professional Version
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Topic Resources

Bacterial vaginosis is a vaginal infection that occurs when the balance of bacteria in the vagina is altered.

  • Women who have a sexually transmitted disease, who have several sex partners, or who use an intrauterine device are more likely to get bacterial vaginosis.

  • Bacterial vaginosis can cause a thin, gray or white discharge, which may be profuse and smell fishy.

  • If symptoms suggest a vaginal infection, doctors examine a sample of the discharge and/or fluid from the cervix and test it for microorganisms that can cause infection.

  • Antibiotics applied as gels or creams or taken by mouth are effective.

  • Bacterial vaginosis commonly recurs.


Many bacteria normally reside in the vagina. One type, called lactobacilli, maintains the normal acidity of the vagina. By doing so, lactobacilli help keep the lining of the vagina healthy and prevent the growth of certain bacteria that cause infections. Bacterial vaginosis, the most common vaginal infection, results when the number of protective lactobacilli decreases and the number of other bacteria that are normally present (such as Gardnerella vaginalis and Peptostreptococcus bacteria) increases.

Why these changes occur and whether the disorder is sexually transmitted are unknown. What is known is that bacterial vaginosis is more common among women who have or do the following:

However, bacterial vaginosis can occur in virgins.

Bacterial vaginosis can develop in women who have sex with women, particularly when they have several sex partners.


In bacterial vaginosis, the vaginal discharge may be gray or white, thin, and profuse. Usually, the discharge has a fishy odor. The odor may become stronger after sexual intercourse and during menstrual periods. Itching, redness, and swelling are not common.

Bacterial vaginosis can lead to serious complications, such as pelvic inflammatory disease and, for pregnant women, infection of the membranes around the fetus (intra-amniotic infection), preterm labor and delivery, and infections of the uterus after delivery or after an abortion.


  • A doctor's evaluation

  • Examination of a sample of the discharge and/or fluid from the cervix

If girls or women have a vaginal discharge that is unusual or that lasts for more than a few days, they should see a doctor.

Doctors suspect bacterial vaginosis based on symptoms, such as a gray discharge that smells fishy. They then ask questions about the discharge and possible causes (such as sexually transmitted diseases).

To confirm the diagnosis, doctors do a pelvic examination. While examining the vagina, the doctor takes a sample of the discharge with a cotton-tipped swab. The sample is examined under a microscope. With information from this examination, the doctor can usually identify the microorganism causing the symptoms. If test results are inconclusive, other newer tests can be done using the samples obtained during the pelvic examination.

Usually, the doctor also uses a swab to take a sample of fluid from the cervix (the lower part of the uterus that opens into the vagina). This sample is tested for sexually transmitted diseases.

To determine whether there are other infections in the pelvis, the doctor checks the uterus and ovaries by inserting the index and middle fingers of one gloved hand into the vagina and pressing on the outside of the lower abdomen with the other hand. If this maneuver causes substantial pain or if a fever is present, other infections may be present.

Did You Know...

  • Some antibiotic creams used to treat bacterial vaginosis weaken latex condoms and diaphragms.


  • Antibiotics

Bacterial vaginosis is treated with an antibiotic (such as metronidazole or clindamycin). Metronidazole taken by mouth for 7 days is the preferred treatment for women who are not pregnant. However, it may have bodywide side effects. Thus, doctors prefer to give pregnant women metronidazole as a vaginal gel or cream (which is inserted into the vagina with an applicator once a day for 5 days). Women who use clindamycin cream cannot rely on latex products (condoms or diaphragms) for birth control because the drug weakens latex.

Another possible treatment is the antibiotic secnidazole. Its advantage is that only one dose is needed.

Bacterial vaginosis usually resolves in a few days but commonly recurs. If it recurs often, antibiotics may have to be taken for a long time.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest


View All
The Breasts
The Breasts
3D Models
View All
Polycystic Ovary Syndrome
3D Model
Polycystic Ovary Syndrome