Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency medical help for new vertigo accompanied by possible signs of stroke, including:
Also seek emergency help for vertigo with high fever, severe headache, neck stiffness, marked drowsiness, or a new rash.
These can be signs of a serious infection.
Arrange urgent, same-day medical assessment if you suddenly lose hearing in one or both ears, even if the ear feels blocked.
Sudden sensorineural hearing loss can resemble labyrinthitis and treatment may be time-sensitive.[2]
Urgent assessment is also appropriate if you cannot keep fluids down, have signs of dehydration, develop discharge or severe pain from the ear, or became dizzy after a head injury.
Routine follow-up is appropriate if balance is not steadily improving, dizziness continues for several weeks, hearing or tinnitus remains troublesome, or attacks keep returning.
These situations are not usually emergencies, but further hearing, balance, or neurological assessment may be useful.
Every sign above is quoted from the sofidex article on Labyrinthitis. If you are not sure, err upward — it is always reasonable to be checked.