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 if the child:
Is at immediate risk of harming themselves or someone else
Has made a specific threat or plan involving serious harm
Has access to a weapon during a crisis
Is so aggressive or distressed that safety cannot be maintained
In an immediate danger, contact local emergency services or go to the nearest emergency department.
Move other people to safety if this can be done without increasing the 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
Seek prompt professional help if aggression is increasing, the child is regularly running away, using substances, being excluded from school, or causing significant harm to relationships or property.
3
Does any of this apply?
Book an appointment
Arrange a routine assessment if irritability, arguing, or defiance has continued for at least six months and is disrupting family life, school, friendships, or activities.
Earlier assessment is reasonable if the behavior is severe or if you are worried about development, learning, sleep, anxiety, depression, or ADHD.
Every sign above is quoted from the sofidex article on Oppositional defiant disorder. If you are not sure, err upward — it is always reasonable to be checked.