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 after a neck injury if you develop:
New weakness in an arm or leg
Trouble walking, severe loss of balance, or poor coordination
Loss of bladder or bowel control
Numbness around the genitals, buttocks, or inner thighs
Difficulty breathing or swallowing
Severe confusion, repeated vomiting, a seizure, or increasing drowsiness
A worsening severe headache after a head impact
After a major collision or fall, avoid unnecessary neck movement until emergency professionals have assessed you, especially if there is severe pain, weakness, numbness, or reduced awareness.
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 medical assessment if you have tingling or numbness, pain spreading down an arm, an electric-shock feeling through the neck or limbs, severe pain that is getting worse, or difficulty sitting upright.
3
Does any of this apply?
Book an appointment
Routine follow-up is appropriate when pain or stiffness is not improving after a few weeks, symptoms interfere with sleep or daily activities, or you need continuing pain medicine.
Persistent dizziness, headaches, concentration problems, anxiety, or flashbacks should also be discussed.
Every sign above is quoted from the sofidex article on Whiplash. If you are not sure, err upward — it is always reasonable to be checked.