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 severe, rapidly increasing pain or tight swelling, particularly with numbness, weakness, pale or cold skin, or loss of movement.
These can indicate reduced blood flow or pressure around nerves and muscles.
Emergency assessment is also needed after a major injury with deformity or an open wound.
Call emergency services for chest pressure or pain with breathlessness, sweating, faintness, nausea, or pain spreading to the arm, jaw, or back.
Do not assume these symptoms are caused by a chest muscle strain.
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 heard a pop and cannot use the affected muscle normally
You cannot bear weight or move a nearby joint
There is extensive bruising, marked swelling, or a visible dent
Pain is worsening rather than settling
The area becomes red, hot, or associated with fever
You take blood-thinning medicine and develop substantial bruising
Dark brown urine after severe muscle injury or extreme exertion needs urgent care.
3
Does any of this apply?
Book an appointment
Arrange a routine assessment if the injury is not steadily improving, keeps returning, or continues to limit sleep, work, walking, or daily activity.
Assessment is also sensible if the injury happened with little force or you are unsure whether it is a strain.
Every sign above is quoted from the sofidex article on Strains. If you are not sure, err upward — it is always reasonable to be checked.