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 if there is:
Immediate risk of suicide, serious self-harm, or harm to someone else
A command hallucination telling the person to do something dangerous
Severe confusion, reduced consciousness, or inability to stay awake
A seizure, new weakness, severe headache, or difficulty speaking
Fever with a stiff neck, marked agitation, or rapidly changing behaviour
Suspected poisoning, overdose, or severe alcohol or drug withdrawal
Move away and seek emergency help if anyone is at risk.
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
Arrange prompt medical assessment for a first episode of hallucinations, delusions, markedly confused thinking, or unexplained major behaviour change.
Early assessment helps identify causes that need treatment.
Seek urgent same-day help if symptoms are rapidly worsening, the person is unable to manage food, fluids, medicines, or basic safety, or there is a sudden change after starting or stopping a medicine or substance.
The article also says
If it is safe, stay with the person, reduce noise and stimulation, and speak calmly.
Do not physically confront them or argue forcefully about their beliefs.
Every sign above is quoted from the sofidex article on Secondary psychosis. If you are not sure, err upward — it is always reasonable to be checked.