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
Seek emergency medical assessment for a new or sudden drooping eyelid, abnormal eye position, double vision, or enlarged pupil.
A serious blood-vessel or brain problem cannot be excluded safely at home.
Call emergency services if symptoms occur with:
A sudden severe headache
Neck stiffness, vomiting, or collapse
Weakness or numbness on one side
Trouble speaking, walking, or staying awake
New confusion or a seizure
Recent significant head injury
Sudden loss of vision
And for anyone, someone who:
has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
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 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
People over 50 should seek urgent same-day care for new double vision or eyelid drooping with a new headache, scalp tenderness, jaw pain while chewing, fever, unexplained weight loss, or any loss of vision.
These may indicate giant cell arteritis.
After urgent causes have been assessed, attend planned follow-up.
Contact your healthcare team sooner if symptoms worsen, the pupil becomes larger, new pain develops, another neurological symptom appears, or recovery does not follow the expected pattern.
And for anyone, someone who:
has a new severe headache unlike any they have had before
Every sign above is quoted from the sofidex article on Cranial mononeuropathy III. If you are not sure, err upward — it is always reasonable to be checked.