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 help for:
A sudden, extremely severe headache that reaches maximum intensity quickly
New weakness, facial drooping, confusion, fainting, or difficulty speaking
A seizure or loss of consciousness
New visual loss, rather than a familiar fully reversible aura
Headache with fever, a stiff neck, or a widespread rash
A severe headache after a significant head injury
Aura-like symptoms that are new, unusually prolonged, or do not fully resolve
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 prompt medical advice if an attack lasts longer than 72 hours, repeated vomiting prevents you from keeping fluids down, or symptoms are becoming steadily more frequent.
New headaches during pregnancy or after childbirth also need prompt assessment.
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 keep returning, interfere with normal activities, or require frequent medication.
Seek review if established treatment is no longer helping or the cycle has changed.
The article also says
Do not assume new neurological symptoms are “just migraine,” even if you have had migraine before.
Every sign above is quoted from the sofidex article on Cyclic migraines. If you are not sure, err upward — it is always reasonable to be checked.