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 difficulty breathing
Chest pain, collapse, or a seizure
New confusion or extreme drowsiness
Little or no urine with rapidly increasing swelling
Swelling of the face or throat, wheezing, or widespread blistering rash
These may indicate severe kidney dysfunction or a serious medicine reaction.
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 if you have a noticeable decrease in urine, new swelling, persistent vomiting, blood in your urine, or unexplained fever and rash after starting a medicine.
These symptoms have several possible causes and need assessment rather than self-diagnosis.
If you have recently been diagnosed, contact your care team promptly if symptoms worsen, you cannot keep fluids down, or your urine output falls.
Keep scheduled blood tests even when you feel better.
Every sign above is quoted from the sofidex article on Interstitial nephritis. If you are not sure, err upward — it is always reasonable to be checked.