Our Health Library information does not replace the advice of a doctor. Please be advised that this information is made available to assist our patients to learn more about their health. Our providers may not see and/or treat all topics found herein.
What is bacterial vaginosis?
Bacterial vaginosis is a mild infection of the vagina caused by bacteria. Normally, there are a lot of "good" bacteria and some "bad" bacteria in the vagina. The good types help control the growth of the bad types. In women with bacterial vaginosis, the balance is upset. There are not enough good bacteria and too many bad bacteria.
Bacterial vaginosis is usually a mild problem that may go away on its own in a few days. But it can lead to more serious problems. So it's a good idea to see your doctor and get treatment.
What causes bacterial vaginosis?
Experts are not sure what causes the bacteria in the vagina to get out of balance. But certain things make it more likely to happen. Your risk of getting bacterial vaginosis is higher if you:
- Have more than one sex partner or have a new sex partner.
You may be able to avoid bacterial vaginosis if you limit your number of sex partners and don't douche or smoke.
Bacterial vaginosis is more common in women who are sexually active. But it can occur if you are not sexually active as well.
What are the symptoms?
The most common symptom is a smelly vaginal discharge. It may look grayish white or yellow. A sign of bacterial vaginosis can be a "fishy" smell, which may be worse after sex. About half of women who have bacterial vaginosis do not notice any symptoms.
Many things can cause abnormal vaginal discharge, including some sexually transmitted infections (STIs). See your doctor so you can be tested and get the right treatment.
How is bacterial vaginosis diagnosed?
Doctors diagnose bacterial vaginosis by asking about the symptoms, doing a pelvic exam, and taking a sample of the vaginal discharge. The sample can be tested to find out if you have bacterial vaginosis.
What problems can bacterial vaginosis cause?
Bacterial vaginosis usually does not cause other health problems. But in some cases it can lead to serious problems.
- If you have it when you are pregnant, it increases the risk of miscarriage, early (preterm) delivery, and uterine infection after pregnancy.
- If you have it when you have a pelvic procedure such as a cesarean section, an abortion, or a hysterectomy, you are more likely to get a pelvic infection.
- If you have it and you are exposed to a sexually transmitted infection (including HIV), you are more likely to catch the infection.
How is it treated?
Doctors usually prescribe an antibiotic to treat bacterial vaginosis. They come as pills you swallow or as a cream or capsules (called ovules) that you put in your vagina. If you are pregnant, you will need to take pills.
Bacterial vaginosis usually clears up in 2 or 3 days with antibiotics, but treatment goes on for 7 days. Do not stop using your medicine just because your symptoms are better. Be sure to take the full course of antibiotics.
Antibiotics usually work well and have few side effects. But taking them can lead to a vaginal yeast infection. A yeast infection can cause itching, redness, and a lumpy, white discharge. If you have these symptoms, talk to your doctor about what to do.
Bacterial vaginosis is caused by an imbalance of the organisms (flora) that naturally exist in the vagina. Normally, about 95% of vaginal flora are lactobacillus bacteria. (These types are unique to humans, different from the lactobacillus in yogurt.) These lactobacilli help keep the vaginal pH level low and prevent overgrowth of other types of organisms. Women with bacterial vaginosis have fewer lactobacillus organisms than normal and more of other types of bacteria. Experts do not yet understand what causes this imbalance.
Although the specific cause isn't known, a number of health and lifestyle factors have been linked to bacterial vaginosis. For more information, see What Increases Your Risk.
Many women with bacterial vaginosis do not have any symptoms. Bacterial vaginosis does not typically cause itching. But it does cause:
- An excessive grayish white vaginal discharge, unlike normal vaginal discharge. Some women describe the discharge as "yellow."
- A bothersome "fishy" odor, which is usually worse after sex (intercourse).
Bacterial vaginosis often clears up on its own. But in some women it doesn't go away on its own. And for many women it comes back after it has cleared up. Antibiotic treatment works for some women but not others.
Your risk of complications from bacterial vaginosis is higher:
- During pregnancy. Compared to pregnant women who don't have it, women who have bacterial vaginosis during pregnancy have a higher risk of early (preterm) delivery or of uterine infection after pregnancy. Also, pregnant women may have an increased risk of miscarriage.
- After gynecological surgery. Women with bacterial vaginosis at the time of an invasive vaginal procedure have an increased risk of developing more serious infection or inflammation, such as pelvic inflammatory disease (PID) or endometritis.
- When exposed to HIV or other sexually transmitted infection. Women who have bacterial vaginosis when they are exposed to sexually transmitted infections (including HIV) have an increased risk of becoming infected with the sexually transmitted infection.
What Increases Your Risk
Things that increase your risk of getting bacterial vaginosis include:
- Having more than one sex partner or having a new sex partner.
- Not using condoms.
Although bacterial vaginosis can be triggered by or get worse from sexual activity, it does not appear to be an infection that is passed from man to woman. So experts do not consider bacterial vaginosis to be a male-female sexually transmitted infection. Bacterial vaginosis may be passed from woman to woman during sexual contact.
When should you call your doctor?
Bacterial vaginosis can be hard to distinguish from other types of vaginal infection. Consider the following if you have any signs of vaginal infection.
Call your doctor immediately if you:
- Develop lower belly pain and a fever higher than 101°F (38.3°C) along with a vaginal discharge.
- Are pregnant and have symptoms of a vaginal infection.
Call your doctor for an appointment within 1 week if you:
- Have vaginal discharge with an unusual or foul odor.
- Have vaginal itching.
- Have pain during sex or during urination.
- Develop any other discomfort or discharge that may mean you have a vaginal infection.
It's generally recommended that you contact or see your doctor about unusual vaginal symptoms.
If your symptoms are due to a sexually transmitted infection (STI) and not bacterial vaginosis, you may infect a sex partner if you delay treatment. You may also develop more serious complications of STIs such as pelvic inflammatory disease (PID).
- To prevent the spread of a possible infection, avoid sex. Wait until after you have seen your doctor.
- Avoid douching.
Who to see
Doctors who can diagnose and treat bacterial vaginosis include:
Exams and Tests
Your doctor may test you for bacterial vaginosis if you:
- Have symptoms.
- Are going to have a hysterectomy or surgical abortion. (Bacterial vaginosis increases infection risk afterwards.)
- Are pregnant and have symptoms.
Your doctor can diagnose bacterial vaginosis based on your history of symptoms, a vaginal exam, and a sample of the vaginal discharge. Laboratory tests to detect signs of bacterial vaginosis may include:
- Wet mount. A sample of vaginal discharge is mixed with a salt (normal saline) solution after placing it on a microscope slide. The prepared slide is examined to identify the bacteria present, to look for white blood cells that point to an infection, and to look for unusual cells called clue cells. The presence of clue cells is one sign of bacterial vaginosis.
- Whiff test. Several drops of a potassium hydroxide (KOH) solution are added to a sample of vaginal discharge to find out whether a strong fishy odor is produced. A fishy odor on the whiff test suggests bacterial vaginosis.
- Vaginal pH. The normal vaginal pH is 3.8 to 4.5. Bacterial vaginosis usually causes the vaginal pH to rise above 4.5.
- Oligonucleotide probes. This test detects the genetic material (DNA) of bacterial vaginosis bacteria. Oligonucleotide probe testing is very accurate but is not routinely available in most labs.
The presence of clue cells, an increased vaginal pH, and a positive whiff test are enough evidence to treat for bacterial vaginosis.
Bacterial vaginosis may be found during a pelvic exam.
Treatment for bacterial vaginosis includes antibiotic medicine (oral or vaginal). Antibiotics kill the problem bacteria causing bacterial vaginosis symptoms. But symptoms often come back after antibiotic treatment.
For some women, bacterial vaginosis goes away without treatment. But when it does not go away even with treatment, bacterial vaginosis is frustrating and troublesome. Bacterial vaginosis makes the reproductive tract vulnerable to infection or inflammation. So your doctor will test and treat you with antibiotics for bacterial vaginosis if you are:
- Having persistent symptoms.
- Pregnant and have symptoms.
- Planning to have a hysterectomy or surgical abortion. Treating bacterial vaginosis with antibiotics beforehand may lower your risk of getting a serious infection afterward.
Talk to your doctor about whether testing is right for you.
What to think about
If your doctor finds other problems during the exam, such as a possible sexually transmitted infection (STI), appropriate treatment will be recommended.
To help prevent bacterial vaginosis:
- Limit the number of sex partners you have.
- Avoid douching.
- Use condoms consistently.
Bacterial vaginosis may be passed between women during sexual contact. If you have a female sex partner, you may benefit from using protection and carefully washing shared sex toys.
Bacterial vaginosis is generally not considered a sexually transmitted infection (STI). But if you are exposed to an STI while you have bacterial vaginosis, you are more likely to get that infection.
It is always important to practice safer sex to prevent sexually transmitted infections, whether or not you have bacterial vaginosis. Preventing an STI is easier than treating an infection after it occurs.
Some women have tried treating bacterial vaginosis with the probiotic Lactobacillus. This is found in foods like yogurt and in dietary supplements. But more research is needed to find out if Lactobacillus works to treat or prevent bacterial vaginosis.
There are also different types of Lactobacillus, and researchers don't yet know which type would be most effective.
The antibiotics metronidazole (such as Flagyl and MetroGel), clindamycin (such as Cleocin and Clindesse), and tinidazole (such as Tindamax) are used to treat bacterial vaginosis. Depending on the antibiotic you are prescribed, you may take it by mouth or use it vaginally.
During pregnancy, women are usually prescribed oral medicine.
When considering treatment for bacterial vaginosis, ask your doctor whether you should:
- Use oral medicine or medicine inserted into the vagina. Some women prefer to take pills rather than using a vaginal medicine.
- Avoid having sex during the time that you are being treated.
- Continue treatment during your menstrual period. Medicine placed in your vagina is harder to use during your period, but your doctor may recommend continuing treatment during this time.
- Avoid drinking alcohol during treatment with metronidazole or tinidazole. These medicines can cause severe nausea and vomiting if you drink alcohol when you are taking one of them. Clindamycin does not.
The oil in clindamycin cream and ovules can weaken latex. This means condoms and diaphragms may break, and you may not be protected from STIs or pregnancy.
Other Works Consulted
- Abramowicz M (2010). Drugs for sexually transmitted infections. Treatment Guidelines From The Medical Letter, 8(95): 53–60.
- American College of Obstetricians and Gynecologists (2006, reaffirmed 2011). Vaginitis. ACOG Practice Bulletin No. 72. Obstetrics and Gynecology, 107(5): 1195–1206.
- Bornstein J (2013). Benign disorders of the vulva and vagina. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 11th ed., pp. 620–645. New York: McGraw-Hill.
- Eckert LO, Lentz GM (2012). Infections of the lower and upper genital tracts: Vulva, vagina, cervix, toxic shock syndromes, endometriosis, and salpingitis. In GM Lentz et al., eds., Comprehensive Gynecology, 6th ed., pp. 519–559. Philadelphia: Mosby.
- Mackay G (2013). Sexually transmitted diseases and pelvic infections. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 11th ed., pp. 701–731. New York: McGraw-Hill.
- Marrazzo J, Sobel J (2010). Vaginal infections. In SA Morse et al., eds., Atlas of Sexually Transmitted Diseases and AIDS, 4th ed., pp. 76–85. Philadelphia: Saunders.
- Soper DE (2012). Genitourinary infections and sexually transmitted diseases. In JS Berek, ed., Berek and Novak's Gynecology, 15th ed., pp. 557–573. Philadelphia: Lippincott Williams and Wilkins.
Current as of: November 8, 2019
Author: Healthwise Staff
Sarah Marshall MD - Family Medicine
Kathleen Romito MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Devika Singh MD, MPH - Infectious Disease
To learn more about Healthwise, visit Healthwise.org.
© 1995-2020 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.