Diagnosis of infectious mononucleosis is based on the above mono symptoms and signs. Infectious mononucleosis can be verified due to blood tests, which may exclude other possible causes of symptoms such as angina. At the beginning of infectious mononucleosis blood tests show an increase in white blood cells (leukocytes). Some of leukocytes are “atypical” and prove infectious mononucleosis.

Specific blood tests such as antibodies tests may prove the diagnosis of infectious mononucleosis. These tests measure antibodies to the Epstein-Barr virus. Unfortunately, antibodies can not be found while the second or third week of illness. Blood biochemical analysis may show hepatic function disorder.