SN explained to patient that Diflucan is used to treat serious fungal or yeast infections, such as urinary tract infections. It works by stopping the growth of Candida. It usually starts to work within one day, but it may take 3 days for your symptoms to improve and up to 7 days for your symptoms to disappear. Nausea, vomiting, diarrhea, stomach upset/pain, headache, dizziness, or hair loss may occur while using Diflucan.