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 vertigo accompanied by possible stroke or another serious neurological problem, including:
New facial drooping, arm or leg weakness, or numbness
New trouble speaking, understanding speech, or swallowing
Double vision, severe loss of coordination, or inability to stand
A sudden severe headache unlike your usual headaches
Fainting, chest pain, or a serious injury from a fall
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 your established symptoms change significantly, attacks become more frequent, you fall, or vomiting makes it difficult to keep fluids down.
New sudden hearing loss in one or both ears needs urgent, same-day assessment because early treatment may matter.
3
Does any of this apply?
Book an appointment
Arrange a routine medical appointment if you have repeated vertigo, fluctuating hearing, one-sided tinnitus, or ear pressure.
These symptoms do not automatically mean Meniere disease, but they should be assessed.
The article also says
Do not assume that a new or unusually severe episode is Meniere disease simply because you have had vertigo before.
Every sign above is quoted from the sofidex article on Meniere disease. If you are not sure, err upward — it is always reasonable to be checked.