The symptoms of an acute kidney infection often develop quickly over a few hours or a day and may include:
- pain in your lower back, abdomen (tummy) or side (it may be only on one side)
- a fever
- shivering and chills
- feeling weak
- feeling sick or vomiting
If you have any of these symptoms, contact your GP.
Around one in three women who get an acute kidney infection have symptoms of a bladder infection as well. This is also called cystitis, or a lower urinary tract infection (UTI). See our frequently asked questions for more information about UTIs.
Your GP will ask about your symptoms and examine you. He or she may also ask you about your medical history. Your GP will ask you to provide a urine sample. He or she will usually do a 'dipstick' test to confirm if you have a urinary infection. Your GP may send your urine sample to a laboratory to find out which type of bacteria is causing the infection.
In you have a severe kidney infection, your GP may recommend you go into hospital for further tests and treatment. Other tests may include:
- a blood sample to see if you have signs of an infection
- scans (such as a CT scan) to check for any problems or obstructions in your ureters or kidneys
It’s important to drink enough fluids to prevent yourself from getting dehydrated. Make sure you get plenty of rest too.
If you need pain relief, you can take over-the-counter painkillers such as paracetamol. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.
Your GP will usually prescribe antibiotics if he or she suspects that you have a kidney infection. It’s important to take the full course of antibiotics, even if your symptoms clear up before you finish them. Your symptoms should start to improve within a day or so. But if they get worse or you don't feel any better within 48 hours of starting treatment, contact your GP.
You may need hospital treatment if you’re:
- unable to keep down fluids or medicines
- not responding to antibiotic treatment
- diagnosed with blood poisoning (septicaemia)
- at risk of developing complications
In hospital, you may have a drip inserted into a vein in your hand or arm to give you fluids and antibiotics.
You may need to have surgery if tests show that you have an obstruction (such as a kidney stone) in your ureters or kidneys.
A kidney infection is usually caused by bacteria such as Escherichia coli (E. coli), which live in your bowel. The bacteria can get into your urinary tract if they spread from your anus to your urethra. The bacteria can enter your urethra and travel up into your bladder and will usually cause a lower UTI or cystitis. The bacteria can then travel up one or both of the tubes that connect your bladder to your kidneys (ureters) and cause a kidney infection.
You can also spread the bacteria when you have sex, as bacteria can enter your urethra. Bacteria and viruses can also be carried in your blood from other parts of your body to your kidney.
Women get more kidney infections than men. This is partly because the urethra is much shorter in women than in men. There is less distance for the bacteria to travel to the bladder.
You're also more likely to develop a kidney infection if you:
- have an abnormal kidney
- have a blocked ureter or kidney, for example by a kidney stone or an enlarged prostate gland
- are pregnant (see our frequently asked questions for more information)
- have diabetes
- have a weakened immune system, for example, if you have HIV/AIDS
- have had a UTI in the past year
- have urinary incontinence
An acute kidney infection can sometimes cause complications including:
- a pocket of pus (abscess) in your kidney – this is called a pyonephrosis
- your kidneys not working properly
- blood poisoning (septicaemia) – this can happen if the bacteria that have caused your kidney infection get into your blood
You're more likely to develop complications if you:
- are pregnant
- have type 1 or type 2 diabetes
- are over 65
- have a persistent kidney infection
- have kidney disease
- have a urinary catheter fitted (a tube that takes urine from your bladder out of your body)
- have a weakened immune system – for example, if you have HIV/AIDS (which reduces your ability to fight infection)
If you often get a kidney infection or a UTI, your GP may advise you to take a low dose of antibiotics every day. How long you need to take them for will depend on your personal circumstances.
You can also develop a kidney infection from cystitis. If you get cystitis, try self-help measures or get prompt treatment to cure the condition. This will reduce the risk of the infection spreading to your kidneys.
If you have a kidney infection when you're pregnant, it may lead to complications, such as:
- kidney damage or even failure
- having a baby with a low birth weight
- premature labour
- blood poisoning
If your GP suspects you have a kidney infection, he or she may send you for tests and treatment in hospital.
Why is a kidney infection more common during pregnancy?
During pregnancy your body undergoes physical changes that can affect how well it gets rid of urine. This can increase your risk of getting a bladder or kidney infection.
As your baby grows, your womb (uterus) puts pressure on your bladder and the tubes that carry urine from your kidneys to your bladder (ureters). This can block the normal flow of urine to your bladder. This means that bacteria in the trapped urine can multiply and cause a kidney or bladder infection.
Hormonal changes in pregnancy and the extra fluid in your bloodstream mean that your kidneys are having to worker harder. Your immune system, which usually defends your body against infections, also changes when you’re pregnant (to stop it attacking your baby). This means that a slight change in the normal functioning of your kidneys can increase your risk of having a urinary tract infection (UTI). This includes a bladder or kidney infection.
Because of this you will be offered urine tests as part of your routine antenatal care. At each antenatal appointment, you will need to provide a urine sample. Your GP or midwife will test your urine for protein and bacteria. Protein in your urine can suggest poor kidney function and bacteria in your urine can suggest a UTI. It's important to provide this urine sample so you can get treatment for an infection early to prevent any problems with your pregnancy.
If I have to go to hospital and I'm given antibiotic treatment through a drip in my arm, can I switch to antibiotic tablets?
Yes, you should be able to switch to antibiotic tablets once you start to recover but it depends on your individual circumstances.
You will usually only need to go into hospital if you have severe symptoms of a kidney infection, or you're pregnant. You may also need to go into hospital if you’re at particular risk of developing complications.
In hospital, you may be given antibiotics and fluids through a drip into a vein (usually in your arm). The reason you’re given antibiotics in this way is so that they can enter your blood directly and reach the infection immediately. The quicker the antibiotics reach the infection, the quicker they can start to kill the bacteria. The sooner the infection starts to clear up, the sooner you will feel better.
Your doctor may decide to switch to antibiotic tablets as your symptoms improve and you’re ready to go home. But this will depend on your individual circumstances and the type of antibiotic treatment you have.
I have heard the terms 'upper UTI' and 'lower UTI'. What do these mean?
Urinary tract infection (UTI) is the name given to an infection of any part of your urinary system. A lower UTI is an infection of your bladder and urethra (the tube that carries the urine from your bladder and out of your body). An upper UTI is an infection of your kidneys and your ureters (the tubes that carry urine from your kidneys to your bladder).
Symptoms of a lower urinary tract infection may include:
- a stinging or burning sensation when you pass urine
- feeling that you need to urinate more often than usual
- feeling that you need to urinate urgently even if you pass very little or no urine
- urine that is cloudy, dark-coloured or has a strong smell
- blood in your urine
- pain or aching in your abdomen (tummy)
If you have a healthy urinary tract, a UTI is unlikely to cause any serious damage to your kidneys. This is called uncomplicated infection.
If you have an obstruction in your kidneys or urinary tract (such as kidney stones), this could be made worse by an infection. This is also the case if you have a condition that may affect your kidneys (such as type 1 diabetes). It can also cause serious damage to your kidneys and sometimes septicaemia (blood poisoning). This is called a complicated infection and you will need to go into hospital for treatment.
- British Kidney Patient Association
- Acute pyelonephritis. Medscape. www.emedicine.medscape.com, published 4 March 2013
- Guidelines on urological infections. European Association of Urology. www.uroweb.org, published 2013
- Pyelonephritis. PatientPlus. www.patient.co.uk/patientplus.asp, published 22 April 2013
- Kidney anatomy. Medscape. www.emedicine.medscape.com, published 4 October 2013
- Management of suspected bacterial urinary tract infection in adults. Scottish Intercollegiate Guidelines Network (SIGN). www.sign.ac.uk, published July 2012
- Pyelonephritis (acute) in non-pregnant women. BMJ Clinical Evidence. www.clinicalevidence.bmj.com, published 13 January 2011
- Pyelonephritis – acute. NICE Clinical Knowledge Summaries. cks.nice.org.uk, published June 2013
- Urinary tract infections in adults. National Kidney and Urologic Diseases Information Clearinghouse. www.kidney.niddk.nih.gov, published November 2011
- Pyelonephritis: kidney infection. National Kidney and Urologic Diseases Information Clearinghouse. www.kidney.niddk.nih.gov, published 11 June 2012
- Male urethra anatomy. Medscape. www.emedicine.medscape.com, published 11 July 2013
- Female urethra anatomy. Medscape. www.emedicine.medscape.com, published 3 April 2012
- Acute pyelonephritis – suspected. Map of Medicine. www.mapofmedicine.com, published 25 April 2013
- Bacterial urinary tract infections. The Merck Manuals. www.merckmanuals.com, published November 2013
- Acute pyelonephritis – secondary care management. Map of Medicine. www.mapofmedicine.com, published 30 August 2011
- Urinary tract infection in pregnancy. The Merck Manuals. www.merckmanuals.com, published June 2013
- The pregnancy book. Department of Health. www.dh.gov.uk, published 2010
- Mor G, Cardenas I. The immune system in pregnancy: a unique complexity. Am J Reprod Immunol 2010; 63(6):425–33. doi: 10.1111/j.1600-0897.2010.00836.x
- Antenatal care. National Institute for Health and Care Excellence (NICE), March 2008. www.nice.org.uk
- Risk factors for complications during pregnancy. The Merck Manuals. www.merckmanuals.com, published October 2013
- Gupta K, Hooton TM, Naber KG, et al. International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: a 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clinical Practice Guidelines 2011; 52(5):e103–e20. doi: 10.1093/cid/ciq257
- Lower urinary tract infection (UTI) in females. Map of Medicine. www.mapofmedicine.com, published 14 October 2013
- Urinary tract infection in adults. PatientPlus. www.patient.co.uk/patientplus.asp, published 22 April 2013
- British Kidney Patient Association
We’d love to know what you think about what you’ve just been reading and looking at – we’ll use it to improve our information. If you’d like to give us some feedback, our short form below will take just a few minutes to complete. And if there's a question you want to ask that hasn't been answered here, please submit it to us. Although we can't respond to specific questions directly, we’ll aim to include the answer to it when we next review this topic.
Let us know what you think using our short feedback form Ask us a question
Reviewed by Rachael Mayfield-Blake, Bupa Health Information Team, March 2014.
Let us know what you think using our short feedback form Ask us a question
About our health information
At Bupa we produce a wealth of free health information for you and your family. We believe that trustworthy information is essential in helping you make better decisions about your health and care. Here are just a few of the ways in which our core editorial principles have been recognised.
Information StandardWe are certified by the Information Standard. This quality mark identifies reliable, trustworthy producers and sources of health information.
Plain English CampaignWe hold the Crystal Mark, which is the seal of approval from the Plain English Campaign for clear and concise information.
What our readers say about us
But don't just take our word for it; here's some feedback from our readers.
“Simple and easy to use website - not alarming, just helpful.”
“It’s informative but not too detailed. I like that it’s factual and realistic about the conditions and the procedures involved. It’s also easy to navigate to areas that you specifically want without having to read all the information.”
“Good information, easy to find, trustworthy.”
Our core principles
All our health content is produced in line with our core editorial principles – readable, reliable, relevant – which are represented by our diagram.
In a nutshell, our information is jargon-free, concise and accessible. We know our audience and we meet their health information needs, helping them to take the next step in their health and wellbeing journey.
We use the best quality and most up-to-date evidence to produce our information. Our process is transparent and validated by experts – both our users and medical specialists.
We know that our users want the right information at the right time, in the way that suits them. So we review our content at least every three years to keep it fresh. And we’re embracing new technology and social media so they can get it whenever and wherever they choose.
Here are just a few of the ways in which the quality of our information has been recognised.
The Information Standard certification scheme
You will see the Information Standard quality mark on our content. This is a certification programme, supported by NHS England, that was developed to ensure that public-facing health and care information is created to a set of best practice principles.
It uses only recognised evidence sources and presents the information in a clear and balanced way. The Information Standard quality mark is a quick and easy way for you to identify reliable and trustworthy producers and sources of information.
Certified by the Information Standard as a quality provider of health and social care information. Bupa shall hold responsibility for the accuracy of the information they publish and neither the Scheme Operator nor the Scheme Owner shall have any responsibility whatsoever for costs, losses or direct or indirect damages or costs arising from inaccuracy of information or omissions in information published on the website on behalf of Bupa.
We comply with the HONcode (Health on the Net) for trustworthy health information. Certified by the HONcode for trustworthy health information.
Plain English Campaign
Our website is approved by the Plain English Campaign and carries their Crystal Mark for clear information. In 2010, we won the award for best website.
Website approved by Plain English Campaign.
British Medical Association (BMA) patient information awards
We have received a number of BMA awards for different assets over the years. Most recently, in 2013, we received a 'commended' award for our online shared decision making hub.
If you have any feedback on our health information, we would love to hear from you. Please contact us via email: email@example.com. Or you can write to us:
Health Content Team
15-19 Bloomsbury Way