If you have what seems to be the flu, with aches, fever, and enlarged lymph nodes, but you also have extreme weakness or fatigue or a very painful sore throat that feels like it is coated in cotton, you may suspect mono. Also, if symptoms last more than a week, you should see a doctor to be tested for mono.

The doctor will perform a physical examination to check your spleen, tonsils, and lymph nodes for signs of infection and will examine your throat for the characteristic white coating of mono. Many cases of mono can be diagnosed based on medical history and a physical examination, but if necessary, the doctor may do a test called a Monospot to check your blood for specific types of antibodies against the EBV. These antibodies peak at weeks two through five of the illness and may persist for several months up to one year. Someone who was previously infected with EBV but does not currently have mono should not have these antibodies in their blood.

The doctor might also order blood tests to look for an elevated white blood cell count with especially high numbers of mononuclear leukocytes (lymphocytes and monocytes) or unusual-appearing white blood cells (atypical lymphocytes). Positive findings on both of these tests are consistent with a diagnosis of mononucleosis but they cannot confirm that the disease is present.