Kidney infection

Also called Pyelonephritis

A kidney infection is a painful and unpleasant illness caused by bacteria travelling from the bladder into one or both kidneys. It is more serious than a bladder infection (cystitis) and needs prompt treatment with antibiotics to prevent kidney damage or sepsis. It is more common in women and during pregnancy.

Last updated Nov 9, 2026

What it is

Most people get better with a course of antibiotic tablets. Some need treatment in hospital.

A urine test after treatment may be done, and repeated infections may need further tests.

Common signs

  • Pain in the side, lower back or around the genitals
  • High temperature and shivering
  • Feeling sick or vomiting
  • Pain or burning when peeing
  • Cloudy, smelly or bloody pee

How it is usually diagnosed

  • Urine test and culture
  • Blood tests
  • Kidney ultrasound if infections keep happening

Records worth keeping

Keeping these together makes each appointment easier, especially when you see a new doctor:

  • Urine culture results
  • Antibiotics used
  • Kidney scan reports
  • Discharge letters

Questions to ask your doctor

  • Which antibiotic do I need and for how long?
  • Do I need any scans?
  • How can I reduce the chance of another infection?

When to get help right away

Call 112 or go to the nearest emergency department if you have:

  • Confusion, fast breathing, cold blotchy skin, very high or low temperature, or being unable to keep antibiotics down: call 112, it may be sepsis

This page is general information. It is not a diagnosis and does not replace a doctor who knows your history. Medfold keeps your records organised; it does not interpret them.

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