Diagnosis of tonsillitis can easily be made by the treating physician based on the history given by the patient and the findings on examination. Examination of the throat in tonsillitis reveals:

Redness and swelling of the tonsils

Pus pockets on the tonsils

Discharge from the tonsils

In case of peritonsillar abscess, there may be a shift of the involved tonsil towards the center of the throat. The uvula may be shifted towards the opposite side (away from the affected tonsil).

The treating physician may order certain tests that will confirm the diagnosis of tonsillitis. These tests include:

Throat swab: This is used to get a sample of the secretion from the back of the throat. The sample is then checked in a laboratory for the presence of bacteria.

Blood tests: This primarily includes a complete blood count (CBC) which is done to confirm the presence of infection.