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:
A headache that reaches maximum intensity within seconds or minutes
New weakness, facial drooping, confusion, fainting, or persistent speech trouble
New loss of vision or severe difficulty walking
Headache with fever, a stiff neck, marked drowsiness, or a seizure
Severe headache after a significant head injury
A new severe headache during pregnancy or soon after giving birth
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
Seek urgent medical advice if an attack lasts longer than usual, repeated vomiting makes it hard to keep fluids down, or neurological symptoms are different from your established aura.
And for anyone, someone who:
has a fever with a stiff neck, a rash that does not fade under pressure, or severe headache
is vomiting and cannot keep fluids down
has a new severe headache unlike any they have had before
3
Does any of this apply?
Book an appointment
Arrange a routine appointment if headaches are recurring, interfering with daily life, or difficult to control.
You should also seek assessment for a new headache pattern, new aura symptoms, headaches that are steadily becoming more frequent, or headache that begins after starting a new medicine.
The article also says
Do not assume sudden or unfamiliar neurological symptoms are migraine, even if you have had aura before.
Every sign above is quoted from the sofidex article on Migraine. If you are not sure, err upward — it is always reasonable to be checked.