Kidney infection - Symptoms, treatment and prevention

Kidney infections are caused by bacteria or viruses in your kidneys. They are considered serious and should be treated right away. Learn about symptoms and prevention.
Medically reviewed by
AKF's Medical Advisory Committee
Last updated
November 4, 2022

When bacteria or viruses get into your kidneys, usually through your urinary tract, they can cause a kidney infection. If you have symptoms such as pain in the sides of your lower back, fever, chills or pain while urinating (i.e., peeing), contact your doctor right away. Kidney infection can be serious if not treated with antibiotics or other medicines. 

What is a kidney infection?

A kidney infection happens when bacteria or viruses get into your kidneys. Kidney infections can affect both or just one of your kidneys. A kidney infection is a type of urinary tract infection (UTI).

What are the symptoms of a kidney infection?

Symptoms of a kidney infection include:

  • Fever
  • Chills
  • Throwing up
  • Feeling sick to your stomach
  • Pain in your lower back, one or both sides or your groin
  • Urinating (peeing) more often than normal
  • Feeling like you have to urinate even if you just went
  • Pain or burning when urinating 
  • Blood or pus (thick, white or yellow liquid) in your urine 
  • Urine that is cloudy or smells bad 
  • Diarrhea

If you notice any of these symptoms, contact your doctor right away. If you are currently taking medicine to treat a UTI, but you are still having any of these symptoms, contact your doctor.

How will I know if I have a kidney infection?

To find out if you have a kidney infection, doctors may do tests such as:

  • Urine tests to look for bacteria or other signs of infection, such as white blood cells, in your urine
  • Blood tests
  • Imaging tests to look at your kidneys, such as an X-ray, ultrasound or CT scan
  • Rectal exam for men, where the doctor inserts a gloved, lubricated finger into the anus to see if the prostate gland is enlarged and blocks the flow of urine

What causes a kidney infection?

The bacteria or viruses that cause kidney infections usually come from another part of your urinary tract, such as your bladder, ureters (the tubes that connect your kidneys to your bladder) or urethra (the tube that urine passes through to leave your body) and spread to your kidneys. Less commonly, the bacteria or viruses come from an infection elsewhere in your body. 

Illustration of the urinary tract which includes the kidneys, ureters, bladder, and urethra.
Illustration of the urinary tract which includes the kidneys, ureters, bladder, and urethra.

Kidney infection can also happen if the flow of urine through your urinary tract is blocked. This can happen due to:

  • Kidney stones
  • An enlarged prostate
  • A problem with the shape of your urinary tract that makes it harder for urine to pass through

A kidney infection is not contagious–you cannot catch one from another person or spread a kidney infection if you have one.

Who is more likely to get a kidney infection?

Anyone can get a kidney infection, but it is more common in some people, such as:

  • Women: A woman's urethra is shorter than a man's. Having a shorter urethra makes it easier for bacteria to get into the urinary tract. The urethra is also closer to the anus (where your stool comes out) in women. Bacteria can spread from the anus or vagina into the urethra, and then travel up the urinary tract. Pregnant women are even more likely to have a kidney infection.
  • People with diabetes
  • People with a weakened immune system: This could be caused by a disease, such as diabetes or HIV, or by certain medicines called immunosuppressives. People who have had a kidney transplant or other organ transplant take immunosuppressives.
  • People who have nerve or spinal cord damage that keeps them from feeling pain in and around their urinary tract: This can keep them from noticing symptoms of a bladder infection, which can lead to a kidney infection.
  • People who use a catheter (a thin, flexible tube) to drain urine from their bladder
  • People with vesicoureteral reflux (VUR): People with VUR have urinary tracts that allow urine to flow backwards from the bladder to the kidneys.



What is the treatment for a kidney infection?

Doctors treat most kidney infections with antibiotics (medicines that kill bacteria). Doctors will often first prescribe an antibiotic that fights the most common types of kidney infection because it is very important to treat a kidney infection right away. Then, they may change the type of antibiotic after they get the results of your blood or urine tests.

Doctors will prescribe an antibiotic medicine based on:

  • What type of bacteria is causing the infection
  • How severe the infection is
  • If you are you are pregnant
  • If you are older than 65
  • If you had problems from certain antibiotics in the past, such as allergic reactions

If you have a very serious infection, you may need to stay in the hospital to get antibiotics through an IV (through a vein). You may also get medicine for pain.

If your kidney infection was caused by a problem with the shape of your urinary tract, you may need to have surgery to correct the problem and prevent future kidney infections.

Seek treatment right away

It is very important to get medical treatment for a kidney infection as soon as possible–do not wait for it to go away on its own. Kidney infections that are not treated soon enough can cause permanent kidney damage or can spread to other parts of your body and cause an even more serious infection, such as an infection in your blood (sepsis), which can be fatal.

If you have pain, talk to your doctor about taking over-the-counter pain medicines. You can also use a heating pad to help with pain. Also, be sure to drink plenty of water. 

When will I begin to feel better?

Once you start treatment, you should start to feel better in a few days. 

Can I have sex while being treated for a kidney infection?
After you have started treatment and your symptoms have gone away, it is usually safe to have sex. Remember to urinate after sex to avoid getting more bacteria in your urinary tract. 

 How can I prevent kidney infections?

You may be able to lower your chance of getting a kidney infection by:

  • Drinking plenty of water
  • Urinating as soon as you feel the need to 
  • Urinating after having sex
  • Wiping from front to back after going to the bathroom, if you are a woman. This helps to keep bacteria from your vagina or anus from getting into your urethra.
  • Avoiding the use of deodorant sprays or douches in your genital area
  • Getting treatment for constipation (trouble passing stool [poop]). Constipation is not a symptom of kidney infection but it can increase your chance of having bacteria in your urinary tract because it can make it difficult to empty your bladder fully.

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