Kidney Infection (Pyelonephritis)
The signs of a kidney infection, and why prompt treatment matters.
Last updated: 2026-09-24
A kidney infection is a urinary tract infection that has reached the kidneys. It needs prompt treatment.
Signs
- Fever and chills
- Flank or back pain
- Burning on urination
- Nausea
Why it matters
Untreated kidney infections can damage the kidney or spread to the bloodstream, so antibiotics are started promptly.
Frequently asked questions
Is a kidney infection an emergency?
It needs prompt medical care — fever with flank pain warrants a doctor visit the same day.