How to diagnose the beginning toenail fungus?

Exam. If the nail is changing color such as white or yellow and starting to thicken. It may be a fungus. The only way to be sure is to have a sample of nail sent for testing at a lab.
Microscope. Dermatologists take scrapings of the debris under the nail and examine them under a microscope for the presence of fungal organisms. Topical antifungal creams seldom work on toenail fungus; see a dermatologist and get a prescription for an oral antifungal.