Bacterial vaginosis

Also known as non-specific vaginosis or gardnerella vaginitis

Key points about bacterial vaginosis

  • Bacterial vaginosis is caused by an overgrowth of bacteria (bugs) that are normally only present in the vagina in small numbers.
  • When these bacteria are present in large numbers they may cause symptoms such as an abnormal discharge or odour.
  • Just like on our skin, it's 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.
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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 in that it may change in colour or amount or have a bad smell. 

Diagnosis is usually made following a medical examination (a discharge or odour is noticed) or by taking a swab of the vaginal discharge. 

In some sexual health clinics, the team can look under the microscope to see what bacteria are present on the swab. In this case results and treatment can be provided during your appointment. Other clinics will send the swab off to the community laboratory to be processed and the results will be available within a few 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 (STIs) at the same time.

Standard treatment for bacterial vaginosis is a 7-day course of antibiotic (metronidazole) tablets. Metronidazole is best taken with meals to reduce possible side effects such as nausea or upset stomach. It's also important NOT to drink alcohol while taking metronidazole, at it may give you a severe hangover.

Should my male partner be treated as well?

Treating the male partners of women with bacterial vaginosis doesn't seem to prevent it coming back so is not recommended.

The exact cause is unknown. It's not known if it's sexually transmitted but it's more common if you have sex with more than one person and often develops after sex with a new partner.

It's also more common for women who:

  • have sex with other women
  • use soapy water or other products to clean inside their vagina
  • smoke. 

Most people don't get any long-term consequences but it can be associated with pregnancy problems, pelvic infections and other sexually transmitted infections. 

It does tend to come back and sometimes a longer cause of treatment is needed to reduce your chance of getting it again.

It's advisable to use a condom for at least a month after your treatment – even if you are only having sex with one partner. This may reduce the chances of it coming back. 

Resources for health professionals

NZSHS STI Management Guidelines for use in primary care 2017(external link)(external link) NZ Sexual Health Society

Continuing professional development


Vaginal discharge and bacterial vaginosis – Dr Nicky Perkins(external link)(external link) Goodfellow Unit, NZ, 2019

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Credits: Adapted from content provided by Auckland Sexual Health Service, Te Whatu Ora

Reviewed by: Healthify editorial team

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