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:
Thoughts of suicide with an intention or plan to act
An immediate risk of harming yourself or someone else
New or severe chest pressure, especially with exertion or spreading pain
Severe breathing difficulty, fainting, new weakness, or trouble speaking
Severe confusion, seizure, or suspected drug overdose
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
Prompt medical assessment is important for a first or unexplained episode of strong physical symptoms.
A clinician can consider whether panic, medication effects, substance use, or a physical condition is responsible.
3
Does any of this apply?
Book an appointment
Arrange a routine appointment if worry, panic, or avoidance is persistent, is causing distress, or is interfering with sleep, work, relationships, travel, or healthcare.
It is also reasonable to seek help if you are relying on alcohol, drugs, or sedative medicines to cope.
The article also says
If you are unsure whether chest pain, breathlessness, or faintness is panic, treat it as a possible medical problem rather than trying to diagnose it yourself.
Every sign above is quoted from the sofidex article on Panic and anxiety disorders. If you are not sure, err upward — it is always reasonable to be checked.