Kidney Infection (Pyelonephritis)
Informed by recognized medical guidance
If symptoms are severe, worsening, or life-threatening, seek urgent medical care now.
Overview
A kidney infection (pyelonephritis) is a type of urinary tract infection that starts in the urethra or bladder and moves up to one or both kidneys. It causes swelling and pain and needs prompt medical treatment to prevent serious complications.
Key facts
- Kidney infections are more common in women than men.
- They often start as a bladder infection that moves upward.
- Untreated kidney infections can lead to permanent kidney damage or life-threatening infection in the blood (sepsis).
- Most people recover fully with a course of antibiotics prescribed by a doctor.
Kidney infections are not as common as simple bladder infections, but they affect about 1 in 100 people each year. They are more common in women, especially those who are pregnant or sexually active.
Anyone can get a kidney infection, but it is most common in women, people with diabetes, those with a weakened immune system, people who have a catheter, and older adults. It can also affect children, especially those with a bladder reflux condition.
Symptoms
- High fever with confusion or difficulty waking up
- Severe pain that does not go away
- Vomiting that prevents you from keeping down any fluids
- Signs of sepsis: fast heart rate, rapid breathing, feeling extremely unwell, or cold hands and feet
- ⚠Symptoms of a kidney infection (back pain, fever, chills) – see a GP or go to an urgent care centre the same day
- ⚠Blood in your urine
- ⚠Pain that gets worse or does not improve with simple pain relief
Common symptoms
- Pain in your lower back, side, or groin – often on one side
- High temperature (fever) and chills or shivering
- Feeling sick or actually being sick
- Pain or a burning feeling when you pee
- Needing to pee more often or urgently
- Cloudy, dark, or smelly urine
- Feeling very tired or weak
Symptoms in children
- High fever
- Vomiting or refusing to eat
- Fussiness or crying more than usual
- Wetting themselves or having accidents
- Pain in the belly or back
- Smelly or unusual-coloured urine
Symptoms in older adults
- Confusion or sudden change in mental state
- Loss of appetite or not drinking enough
- Fever or chills
- Low energy or feeling very tired
- Pain in the lower back or side
- Changes in urination (frequency, urgency, leakage)
Causes
Main causes
- Bacteria (usually from your bowel) entering the urethra and moving up to the bladder and then to the kidneys
- A bladder infection that is not treated or does not clear up completely
- Blockage in the urinary tract, such as a kidney stone or an enlarged prostate, that stops urine from flowing properly
Risk factors
- Being female – the urethra is shorter, making it easier for bacteria to reach the bladder
- Sexual activity, which can push bacteria into the urethra
- Pregnancy – changes in the urinary tract make infections more likely
- Diabetes or a weakened immune system
- Using a urinary catheter
- Having a condition that blocks urine flow, like kidney stones or an enlarged prostate
- Previous urinary tract infections
When to see a doctor
See a doctor urgently if:
- If you have symptoms of a kidney infection (pain in your back or side, fever, chills) – contact your GP or NHS 111 today
- If you are pregnant and have any signs of a urinary tract infection
- If you are an older adult or have a weakened immune system and develop these symptoms
Book a routine appointment if:
- If you have repeated bladder infections that do not go away with treatment
- If you notice blood in your urine (even a small amount) and do not have other urgent symptoms
Diagnosis
A doctor will ask about your symptoms and medical history. They will press on your tummy and back to check for pain. They will usually order a urine test to check for bacteria and infection. Sometimes they may do a blood test or an imaging test to look at your kidneys.
Tests that may be done
- Urine sample – sent to a lab to see if bacteria are present and to find out which antibiotic will work best
- Blood tests – to check for signs of infection in your blood and how well your kidneys are working
- Ultrasound or CT scan – to look for blockages like kidney stones or an abscess
What to expect at your appointment
You will need to give a urine sample (a clean catch). The doctor may also take a blood sample. These are quick and not painful. If you are very unwell, you may be admitted to hospital for intravenous (through a drip) treatment and observation.
Treatment
Kidney infections are treated with antibiotics (medicines that kill bacteria). The type and length of treatment depend on how severe the infection is and your general health. Most people can take antibiotic tablets at home, but some people need to stay in hospital for stronger antibiotics through a drip and extra fluids.
Self-care at home
- Drink plenty of water (unless your doctor tells you not to) to help flush out bacteria
- Rest as much as you can – your body needs energy to fight the infection
- Take simple pain relief such as paracetamol or ibuprofen (if safe for you) for pain and fever
- Use a hot water bottle or heat pad on your back or side for comfort (wrapped in a towel to avoid burns)
Medical treatments
Antibiotics are the main treatment. Doctors will prescribe a course that usually lasts 7 to 14 days. It is important to finish the whole course even if you start to feel better. If you are very unwell or cannot tolerate tablets (e.g., due to vomiting), you may be admitted to hospital for antibiotics given through a drip and intravenous fluids. For severe infections or if a blockage is found, you may need additional procedures (see 'whenSurgery' below).
When is surgery considered?
Surgery is rarely needed for a simple kidney infection. However, if there is a blockage causing the infection (such as a large kidney stone or an abscess), a doctor may need to drain the abscess or remove the blockage. This might involve a procedure called a nephrostomy (a tube placed through the skin into the kidney) or ureteroscopy, depending on the cause.
Living with this condition
Most people feel better within a few days of starting antibiotics. However, it can take 1 to 2 weeks to fully recover. During this time, take it easy, drink plenty of fluids, and follow your doctor’s advice. Do not try to go back to all your usual activities too soon – listen to your body.
Lifestyle tips
- Drink enough water throughout the day to keep your urine pale
- Go to the toilet as soon as you feel the need – do not hold it in
- Wipe from front to back after using the toilet to prevent bacteria from spreading
- Empty your bladder fully each time you pee
- Wear cotton underwear and avoid tight-fitting trousers
Diet and exercise
There is no specific diet for kidney infections, but eating a balanced diet can support your immune system. Avoid alcohol while on antibiotics and for a few days after. Gentle exercise like walking is fine once you feel up to it, but do not overdo it. If you feel tired, rest.
Mental health and emotional wellbeing
Being ill with a kidney infection can be stressful and tiring – it is normal to feel anxious or low while you recover. Talk to your doctor if you feel overwhelmed. You can also call a mental health helpline or talk to someone you trust. Remember that your mood will likely improve as your body heals.
Prevention
You can reduce your risk of getting a kidney infection by preventing lower urinary tract infections. Many of the same lifestyle tips help – drink plenty of water, pee after sex, avoid holding urine for too long, and wipe from front to back. If you get frequent UTIs, your doctor may suggest preventive approaches such as a low-dose antibiotic or a vaginal oestrogen cream (for postmenopausal women).
Vaccines
There is no vaccine specifically for kidney infections. However, staying up to date with recommended vaccines (like the flu and pneumococcal vaccines) can help prevent other infections that might weaken your body’s defences.
Screening programmes
There is no routine screening test for kidney infections in healthy people. However, if you have certain risk factors (such as diabetes, pregnancy, or a history of kidney stones), your doctor may check your urine regularly for signs of infection.
Complications
If left untreated
- Permanent kidney damage (scarring) that can lead to chronic kidney disease or high blood pressure
- An abscess (a pocket of pus) in or around the kidney
- Sepsis – a life-threatening infection that spreads into your blood and can cause organ failure
- In pregnancy, a kidney infection can increase the risk of preterm labour and low birth weight
Long-term outlook
With prompt treatment, most people with a kidney infection recover fully without any lasting problems. The outlook is excellent if you see a doctor early and take your full course of antibiotics. If you have a condition that increases your risk (like diabetes or a blocked urinary tract), your doctor will help you manage it to reduce the chance of future infections.
Find support
International organisations
Local organisations
- Kidney Health Australia ↗ · Australia
Helplines
External links open third-party websites. Ruqelo Health is not responsible for external content. Listing an organisation does not imply endorsement.
Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
Related conditions
Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 16, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.
Guidance may differ by country or region. Confirm local recommendations with a qualified healthcare provider.