Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services for:
Sudden or severe upper-left abdominal pain
Abdominal pain with left shoulder pain, dizziness, or fainting
Trouble breathing or noisy breathing
Inability to swallow saliva
Confusion, collapse, or a seizure
These symptoms can indicate spleen rupture, severe airway swelling, or another complication requiring immediate assessment.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek prompt medical advice if:
You cannot drink enough or are passing very little urine
Fever or throat symptoms are worsening rather than improving
Your skin or eyes become yellow
Abdominal discomfort develops
Symptoms improve and then return
Fatigue remains severe or unexplained over time
And for anyone, someone who:
has a fever with a stiff neck, a rash that does not fade under pressure, or severe headache
has a wound that is hot, spreading red, or leaking pus
3
Does any of this apply?
Book an appointment
Arrange a routine medical assessment if you think you may have mono, especially if you have a severe sore throat, swollen neck glands, ongoing fever, or fatigue that is disrupting daily activities.
Testing may be needed because several infections can cause similar symptoms.
Every sign above is quoted from the sofidex article on Infectious mononucleosis. If you are not sure, err upward — it is always reasonable to be checked.