First the Facts

  • Bacterial vaginosis (BV) is a common cause of vaginal discharge.
  • BV is not a sexually transmitted infection (STI).
  • You cannot get BV if you have a penis.
  • The cause of BV is not fully understood, but it occurs when the ‘healthy’ mix of vaginal bacteria is disturbed.
  • BV can resolve by itself, and mild cases do not always need treatment. It can be treated with antibiotics, and treatment is especially important if you are pregnant or you are about to undergo a gynaecological procedure (including getting a ‘coil’ fitted) or fertility treatment.

What Causes Bacterial Vaginosis?

  • The cause of BV is not fully understood, but we do know it is related to the mix of vaginal bacteria.
  • In the vagina there is a ‘healthy’ mix of bacteria with predominance of lactobacilli. This creates an acid environment, preventing the other bacteria from overgrowing.
  • BV occurs when this mix of bacteria is altered, with a reduction in lactobacilli enabling overgrowth of other bacteria.
  • BV is more common if you:
    • Use soaps or perfumes
    • Use a strong washing detergent
    • Perform vaginal douching
    • Smoke
  • Some other factors may also play a part: for example in association with bleeding (menstrual period), genetic factors, the copper intrauterine device (IUD) and after sex if you have not used a condom (as the semen is alkaline).

How Will I Know If I Have Bacterial Vaginosis?

  • Around 50% of women do not have any symptoms.
  • Changes to vaginal discharge may occur:
    • Fishy smell
    • White/grey colour
    • Thin and watery consistency
  • Symptoms can be worse after sex
  • People with BV do not usually experience itching or soreness

Where and When Can I Get a Test?

  • If you have symptoms of BV, you should speak to your nurse or doctor, who may offer you a test. It is particularly important to seek advice if you are pregnant.
  • You may be also offered a test to rule out STIs such as chlamydia or gonorrhoea, as these STIs can sometimes have similar symptoms.
  • Sometimes your healthcare professional may be comfortable diagnosing BV without a test.
  • There are different ways of testing for BV:
    • The healthcare professional may examine you with a speculum and take a swab (like a small cotton bud) from inside your vagina.
    • It may be possible to perform a pH test using litmus paper.
    • Some specialist genitourinary medicine (GUM) clinics will be able to look at a sample under a microscope.
  • You can get a test at:
    • A sexual health, GUM or contraception clinic
    • Some young person’s clinics
    • Your GP surgery

What Happens If I Have Bacterial Vaginosis?

  • You may need treatment if you have symptoms. However, if you have no symptoms or very mild symptoms you may not need antibiotic treatment.
  • Antibiotic treatment is usually with metronidazole. It can be taken as a single dose or over the course of a week. You must not drink alcohol when taking metronidazole (and for 48 hours afterwards) as this can lead to vomiting.
  • Alternatively you may be given an antibiotic gel to use in the vagina for one week. Gels and creams can weaken latex condoms, diaphragms and caps, so speak to your healthcare professional if you rely on these for contraception.
  • You may also be offered testing to check for STIs if you have not already had this.
  • Your healthcare professional will also give you advice on steps you can take at home:
    • Do not use soaps, shower gel or bubble bath to wash around the vagina (washing with water is the best option), and do not wash more than once per day.
    • Having showers rather than baths may help.
    • Do not wash inside the vagina (douching).
    • Do not wash your underwear with strong detergent.
    • Heavy periods may make BV more likely to return, so treating this can help.
    • Using a condom during sex can help (as sperm is alkaline).
    • Wear cotton underwear that is not too tight and avoid tight trousers / tights.
    • Treatment can be provided over the counter using products which contain lactic acid and glycogen (which helps the production of more lactic acid) to return the acid environment in the vagina.

What If I Don’t Get Treated for Bacterial Vaginosis?

  • In many people, BV goes away by itself.
  • BV may slightly increase your risk of developing an infection in the pelvis (pelvic inflammatory disease (PID)).
  • If you are having a gynaecological procedure (including getting a ‘coil’ fitted), and you have BV, this increases the risk of PID.
  • Having BV in pregnancy can slightly increase your risk of complications, e.g. miscarriage, premature (early) labour, low birth weight baby. If you are pregnant and have symptoms of BV, tell your healthcare professional.
  • If you have BV, you are more likely to be infected with HIV if you have sex with a person who is HIV-positive. It is thought that the usual acidic environment of the vagina protects against this, so if the vagina becomes less acidic (as with BV), this protection is lost.


Written by: Dr Nikki Kersey and Dr Paula Briggs
Last updated: January 2021

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