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 now if the person:
Is unconscious, difficult to wake, or suddenly confused
Is not breathing normally or has severe trouble breathing
Has a seizure, collapses, or develops severe weakness
May have inhaled carbon monoxide or dangerous fumes
Has taken an unknown amount or a potentially life-threatening substance
Has a suspected opioid overdose
Was poisoned intentionally or may harm themselves
A specialist can tell you whether home observation, clinic assessment, or emergency care is appropriate.
And for anyone, someone who:
you believe has taken an overdose or swallowed something poisonous
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
2
Is any of this happening?
Be seen today
Call a poison centre promptly for any suspected exposure, even if there are no symptoms.
3
Does any of this apply?
Book an appointment
Routine follow-up is appropriate after discharge for improving but persistent symptoms, medicine review, workplace documentation, or emotional support.
Seek earlier advice if symptoms return or worsen.
The article also says
Do not transport the person in a private vehicle if they may become unconscious, need breathing support, or could contaminate the vehicle.
Every sign above is quoted from the sofidex article on Poisoning first aid. If you are not sure, err upward — it is always reasonable to be checked.