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 or go to an emergency department if pain follows a major injury or occurs with fainting, confusion, severe weakness, cold or clammy skin, chest pain, or trouble breathing.
Sudden severe flank, back, or abdominal pain with collapse also needs emergency care.
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 same-day medical care if flank pain occurs with:
Fever or shaking chills
Burning or pain when urinating
Blood in your urine
Repeated vomiting or trouble keeping fluids down
Difficulty urinating or passing very little urine
Severe pain that does not settle
Pregnancy or possible pregnancy
A single functioning kidney, kidney disease, or a weakened immune system
These may indicate infection, blockage, or another problem needing prompt treatment.
And for anyone, someone who:
has abdominal pain that is severe, constant, or getting worse
3
Does any of this apply?
Book an appointment
For non-urgent pain, book an appointment if it lasts more than a few days, keeps returning, wakes you from sleep, or limits normal activities.
Seek assessment for unexplained weight loss, a new rash, or ongoing urinary changes.
Every sign above is quoted from the sofidex article on Flank pain. If you are not sure, err upward — it is always reasonable to be checked.