How long do symptoms of mono last?
Patient: My son was diagnosed with mono over 2 months ago.  Symptoms constant lethargy hungry but unable to eat any decent amount.  These symptoms were an entire two months before he was diagnosed.  I feel like he should be better by now, and his symptoms seem atypical:  no fever and no vomitting, but constant upset stomach and complaining of heartburn....only 18 years old???? Doctor: Hello.If I understood weel, your son is diagnosied an infectious mononucleosis and symptomes last for 4 months by now. It is a bit too long duration of illnes, since it usually resolves in few weeks.You should contact doctor and do check-up.All the best.