Most healthcare providers test for BV in one of two ways:
- Gram Stain -
For this test, a swab is taken from the vagina, stained, and examined under a microscope. The doctor is looking to see whether the healthy lactobacilli of the vagina have been replaced by the “bad” bacteria characteristic of BV.
- Clinical Criteria -
If a woman has three of the four following criteria, she is considered to have BV:
- Runny white vaginal discharge
- ”Clue Cells” present in a sample of her vaginal fluid – these are cells covered with the organisms characteristic of BV, which can be seen under a microscope.
- Vaginal pH of >4.5
- Discharge with a fishy odor – either before or after the addition of 10% KOH. This is called the whiff test, and it works because the bacterial compounds that produce the fishy odor smell more strongly at higher pH. This is also why women with BV have a more noticeable odor after vaginal intercourse.

