Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek emergency care for severe trouble breathing, chest pain, fainting, a seizure, new severe confusion, or an inability to wake normally.
And for anyone, someone who:
Contact a clinician promptly for a clear decrease in urine, increasing swelling, repeated vomiting, worsening weakness, or difficulty keeping fluids down.
These symptoms can occur with serious fluid, electrolyte, or underlying medical problems and should not wait for a routine appointment.
And for anyone, someone who:
Follow-up depends on the severity of the injury, whether dialysis was needed, and how close kidney function is to its previous level.
A clinician may repeat blood and urine tests, check blood pressure and fluid status, and review all medicines after discharge.
Routine follow-up may include monitoring creatinine, potassium, urine protein, and blood pressure.
A kidney specialist may be involved when recovery is incomplete, the cause remains uncertain, dialysis was required, or there is significant underlying kidney disease.
The article also says
Ask before restarting medicines that were held during the illness.
This may include certain blood pressure medicines, diuretics, or medicines affected by kidney function.
Avoid starting pain relievers, supplements, herbal products, or high-dose vitamins without checking whether they are safe for the kidneys.
Every sign above is quoted from the sofidex article on Acute tubular necrosis. If you are not sure, err upward — it is always reasonable to be checked.