The diagnosis is made by examining a wet smear under microscope or by culture.
A sample of vaginal fluid is seen under a microscope either by staining or under a special lighting, to look for bacteria associated with Bacterial vaginosis.
1· Vaginosis is diagnosed if any three of the following conditions are present:

A clear background.

Absence of lactobacilli.

Presence of numerous "clue cells" (bacteria’s that adhere to the squamous epithelial cells that line the vagina giving them a fuzzy border, hence called clue cells).

Presence of Gardnerella bacteria under the microscope.
2· Characteristic Vaginal
discharge

A characteristic fishy odour when a drop of vaginal discharge is mixed with a drop of 10% potassium hydroxide.
3· Amine Test: Shows raised vaginal pH when a narrow range indicator paper is used.