How do i know my yeast infection is gone ?

Re-examination by MD: If your symptoms are no longer present (itching/discharge) it is likely that the infection is resolved. However, the only "surefire" way to know is to be re-examined by a MD who can take a swab of the area for microscopic or lab examination.

Yeast infection: Generally, you will know the infection is cleared when you no longer have symptoms. If symptom free, there is generally no reason to be seen again for testing.