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 symptoms that could mean a stroke, heart attack, pulmonary embolism, or another serious clot.
These include:
Sudden weakness or numbness, especially on one side
A drooping face, new speech difficulty, or sudden confusion
Sudden severe chest pain, pressure, or shortness of breath
Coughing up blood, fainting, or severe unexplained breathlessness
A suddenly cold, pale, painful, or weak arm or leg
Heavy bleeding that will not stop
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 assessment for new pain, warmth, redness, and swelling in one leg or arm.
These can be signs of a deep vein thrombosis.
Do not wait for the next routine appointment if new symptoms are significant or worsening.
3
Does any of this apply?
Book an appointment
Routine follow-up is appropriate when you feel stable and are attending planned blood tests and treatment visits.
The article also says
Contact your usual care team soon for increasing headaches, worsening itching, new bruising or bleeding, repeated nosebleeds, growing discomfort under the left ribs, unexplained weight loss, fever, drenching night sweats, or a major change in energy.
Every sign above is quoted from the sofidex article on Polycythemia vera. If you are not sure, err upward — it is always reasonable to be checked.