What tests can my doctor do to diagnose cellulitis?

None or cultures. Cellulitis is a clinical diagnosis, which means doctors may diagnose it on history and physical exam alone. Cellulitis has a characteristic look and presents as an area of redness, swelling and warmth. Doctors can do wound or blood cultures, but these tests will not help make a definitive diagnosis of cellulitis.
Blood culture . Test blood to r/o blood infection and check CBC and differential but most cases od cellulitis are diagnosed by a localized redness , swelling and pain of the affected skin site.