Bacterial vaginosis

Also known as non-specific vaginosis or gardnerella vaginitis

Bacterial vaginosis is an infection in a woman’s vagina caused by an overgrowth of bacteria.

Just like on our skin, it is normal to have bacteria within the vagina. However, with bacterial vaginosis, the ‘normal or good’ bacteria are taken over by other bacteria. This change in balance results in the symptoms some women experience.

Who is at risk?

It is not completely understood why some women develop bacterial vaginosis and others don’t. It is more common:  

  • in women with more than one sexual partner
  • when women change sexual partner
  • in women who have sex with other women.

It is also possible that the problem bacteria can be transmitted on fingers or sex toys.


Some women have no symptoms and bacterial vaginosis is found during examination for something else such as a cervical smear test. Other times women notice an abnormal vaginal discharge or an unusual odour which may be worse after unprotected sex.


Diagnosis is usually made following a medical examination (a discharge or odour is noticed) or by taking a vaginal swab test. Another clue can be a change in the normal acidity of the vaginal fluid to become more alkaline.

In some sexual health clinics, the team can look under the microscope to see what bacteria are present on the swab. Most other clinics send the swab off to the community laboratory to be processed. Results are normally available in two to three working days.

If you do have bacterial vaginosis, ask if you can have a full sexual health check as it is common to have chlamydia or other sexually transmitted infections at the same time.


Treatment for bacterial vaginosis varies depending on several factors. If a woman does not have any symptoms, in most cases no treatment is needed. However, if a woman is about to have a gynaecological procedure (such as insertion of an intrauterine device or termination of pregnancy) where the risk of infection spreading to the womb (uterus) is higher, then any bacterial vaginosis infection should be treated first.

Standard treatment for bacterial vaginosis is a seven-day course of metronidazole tablets. Metronidazole is an antibiotic and is best taken with meals to reduce possible side effects such as nausea or upset stomach. It is also important NOT to drink alcohol while taking metronidazole, otherwise people can suffer severe hangover effects.

Alternative treatments include vaginal creams or other antibiotics, but these may not work as well.

Does my partner need to be treated?

Treating the male partner of an infected woman does not seem to prevent recurrences so is NOT routinely recommended.

Can bacterial vaginosis recur?

Yes, bacterial vaginosis can recur, sometimes within a few weeks. If this happens, see your nurse or doctor for further treatment. This may include a longer course of antibiotics and checking for any other infections.

To prevent bacterial vaginosis recurring you could consider temporarily avoiding sexual contact or, if you have sex with a new partner, making sure he uses a condom.

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