Kidney infection

Also known as pyelonephritis

Key points about kidney infection

  • A kidney infection (pyelonephritis) is a painful condition usually caused by a common infection of your bladder.
  • Symptoms include fever and chills, lower back pain, lower tummy pain, nausea or vomiting, loss of appetite, needing to pee more often or a burning sensation when peeing.
  • If not treated urgently with antibiotics, the infection can cause sepsis and permanent damage to your kidneys.
  • A severe kidney infection may need hospital admission and intravenous antibiotics.
  • There are things you can do to help prevent kidney infection, eg, drinking plenty of water, making sure you keep your genitals clean and peeing after sex.


Man on couch with kidney pain and nausea
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Symptoms of a kidney infection include:

  • fever and chills
  • pain in your lower stomach area, or pain in your lower back (either on one or both sides)
  • your urine (pee) is pink or cloudy or smells bad
  • a painful or burning sensation when you pee
  • an urgent need to pee
  • needing to pee more often than usual
  • blood in your pee
  • nausea (feeling sick) or vomiting (being sick)
  • loss of appetite
  • weakness or tiredness
  • confusion, especially in older people.

These symptoms usually occur suddenly, over a day or two. If the infection is serious and untreated, a kidney infection can cause sepsis, which is life threatening.

See your healthcare provider or go to the nearest emergency department immediately if you or someone you care for experiences these symptoms as they may indicate sepsis:

  • slurred speech or confusion
  • extreme shivering or muscle pain
  • passing no urine (pee/mimi) for a day
  • severe breathlessness
  • feeling like you are going to die
  • skin mottled or discoloured.

Call Healthline free on 0800 611 116 if you are unsure what to do. Ask ‘Could this be sepsis?’ 

If you have been given antibiotics and are feeling worse or have more of the symptoms above, contact your GP or go to the nearest emergency department. Don't wait until the morning.

A kidney infection is caused by bacteria, often E. coli. They get into your urethra (the tube that you pee through) and move up to your bladder and ureter (the tube that connects your bladder to your kidneys) and then into your kidneys.

Often you will have a urinary tract infection (UTI) or cystitis (infection of your bladder) at the same time or before you have a kidney infection. However, you can develop a kidney infection without a UTI or cystitis if you have kidney stones, diabetes or a weakened immune system.  

Kidney infections tend to be more common in women than men. This is because a woman’s urethra is shorter, so the bacteria is more likely to reach the kidneys.

Pyelonephritis is more common if you:

Your doctor will talk to you about your symptoms and examine you. If they think you might have a kidney infection, you may be asked to provide a urine (pee) sample to test for bacteria, blood or pus. Your doctor may also ask for a blood test that checks for bacteria or other organisms in your blood and a kidney function test. You may also need an ultrasound scan of your kidneys while you are sick or after you have recovered.

A kidney infection needs to be treated urgently with antibiotics. If it's not treated quickly, the infection can get worse and cause sepsis. This can cause permanent damage to your kidneys and can even lead to death.

The infection usually starts to clear up within a few days of taking the antibiotic, but you must take the entire course of antibiotics to make sure the infection is completely cleared.

Your antibiotic may need to be changed to a different one after few days if:

  • you are not getting better or
  • your urine test results show a different antibiotic is needed.

For a severe kidney infection, your doctor may admit you to the hospital. Treatment in hospital may include antibiotics that you receive through a vein in your arm (intravenously). You may also be prescribed medicine such as paracetamol for pain and fever.

It is helpful to drink plenty of fluids. This helps flush bacteria from your urinary tract. Avoid coffee and alcohol until your infection has cleared, as these can irritate your bladder.

The following simple measures can help to prevent kidney infections:

  • Drink plenty of water to flush bacteria out of your urethra and bladder. Drink 1.5 to 2 litres a day and aim for pale yellow urine.
  • Don't delay peeing – avoid 'holding on'.
  • Make sure your bladder is as empty as possible every time you go.
  • Women should always wipe from the front (vagina) to the back (anus) after going to the toilet.
  • Pee before and soon after sexual intercourse.

The following links provide further information on kidney infection. Be aware that websites from other countries may contain information that differs from NZ recommendations.

Pyelonephritis (kidney infection)(external link) HealthInfo Canterbury, NZ
Kidney infection(external link) NHS, UK
Pyelonephritis(external link) Patient Info, UK


  1. Pyelonephritis(external link) Auckland Regional HealthPathways, NZ, 2019
  2. Pyelonephritis(external link) Patient Info, UK

Acute pyelonephritis(external link) POAC Guideline, NZ, 2017
Gentamicin(external link) NZ Hospital Pharmacists’ Association, NZ, 2015
Pyelonephritis(external link) Patient Info, UK

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Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Dr Arna Letica, FRNZCGP, Auckland

Last reviewed:

Page last updated: