How Long Does It Take a UTI to Turn Into a Kidney Infection?

  • Medical Reviewer: Dany Paul Baby, MD
Medically Reviewed on 4/14/2022

What are kidney infections?

Failing to treat a urinary tract infection can lead to serious health problems, including kidney infections. If you have lingering symptoms, or recurrent UTIs, it is important to see your medical provider.
Failing to treat a urinary tract infection can lead to serious health problems, including kidney infections. If you have lingering symptoms, or recurrent UTIs, it is important to see your medical provider.

Kidney infections, also referred to as pyelonephritis, are a serious type of urinary tract infection (UTI). This infection occurs when bacteria enter the urinary tract, spread to the bladder, and then continue spreading until they reach one or both kidneys.

Kidneys are vital organs in your body since they are responsible for trapping and removing waste products and toxins through urine. Depending on the individual, you may start experiencing symptoms of kidney infection as soon as two hours after your kidneys get infected.

Kidney infections usually occur when the bacteria multiply and are not treated in time. Fortunately, most complications can be avoided with quick treatment.

Can a UTI become a kidney infection?

The urinary system doesn’t ordinarily contain bacteria. However, bacteria such as Escherichia coli (E. coli) and others found in the intestines can get into the urinary tract. This can cause cystitis (inflammation of the bladder), and it can also cause a UTI.

If a UTI spreads to the kidneys, they may fail to function properly. As a result, your blood can easily get infected, which may lead to a life-threatening condition called sepsis.

Frequent bladder infections, structural problems in the urinary tract, or blockage by kidney stones can easily lead to kidney infections as well. The normal flow of urine is from the kidneys down to the bladder. If the urine flows in the wrong direction, kidney infections may also occur.

Causes of UTIs

Having bacteria in the bladder will not always cause a UTI. Other factors also contribute to high chances of contracting UTI. These include:

Sex. A woman has a shorter urethra compared to a man. This allows the bacteria to quickly access the bladder. The urethral opening of a woman is also close to the anus and vagina, which are common sources of bacteria. Bacteria can easily spread to the urethral opening during sexual intercourse.

Lack of enough water in the body. Your body requires a lot of water to flush out any bacteria and waste in your body. Less water in the body causes bacteria to stay and multiply in the bladder.

Holding urine for long periods. Holding urine for a long period of time encourages bacteria to build up. This increases the chance of contracting UTIs.

Hormonal changes during pregnancy. When hormonal changes occur during pregnancy, that makes it easier for bacteria to spread through the urinary tract, causing UTIs.

Conditions blocking normal urine flow. Sexual intercourse, kidney stones, an enlarged prostate, or a tumor can easily block the flow of urine, making room for infection.

Diabetes or a weak immune system. People with diabetes and weak immune systems are at risk since their immune systems are often not strong enough to fight off infections.

Use of catheters. These are tubes placed in the urethra and bladder to help drain urine.

Symptoms of a urinary tract infection

Symptoms of UTI include:

  • A painful or burning sensation when peeing
  • Fever
  • Cloudy, foul-smelling pee, sometimes containing blood
  • A frequent urge to pee, only to pass a very small amount
  • Waking up several times at night to pee

If left untreated, a UTI can quickly advance into a kidney infection.

Symptoms of a kidney infection

Symptoms of a kidney infection may vary depending on your age. If you are dealing with a UTI and experience any of the following symptoms, visit your doctor immediately.


How much urine does the average adult pass each day? See Answer

Diagnosis of a kidney infection

Your doctor will use your medical history, physical examination, and tests to confirm the presence of an infection in your kidneys. They may ask if you have a history of health conditions that are more likely to develop into kidney infections. During a physical examination, your doctor will ask about the symptoms you have been experiencing.

Your doctor may require the following lab or imaging tests to diagnose kidney infection:

Lab tests

Urinalysis. Your doctor will ask you to collect urine in a special container. Then, they will check the sample under a microscope for bacteria or white blood cells produced by the body to fight infection. Bacteria can be present in the urine of healthy people, so a kidney infection is diagnosed based on your symptoms in addition to the lab results.

Urine culture. This test is used to check for bacteria or germs present in your urine that can cause a urinary tract infection. Your doctor will see how much the bacteria have multiplied in a span of 1 to 3 days and then determine the best treatment for you.

Imaging tests

Imaging tests such as a computed tomography (CT) scan, magnetic resonance imaging (MRI), or ultrasound are among other procedures commonly performed to help diagnose a kidney infection.

Treatment of kidney infection

Kidney treatments involve 7 to 14 days of antibiotic administration. However, the symptoms of kidney infection typically start disappearing after a few days of treatment. However, it’s important to finish the dose as prescribed by your doctor to prevent the chances of recurrence of the infection.

Your doctor may give you painkillers like paracetamol to treat pain and fever. If the pain is severe, stronger painkillers may be needed.

Non-steroidal anti-inflammatory painkillers are not recommended for a patient with a kidney infection. NSAIDs such as ibuprofen and aceclofenac can negatively affect how an infected kidney functions.

Sometimes, a doctor may prescribe antibiotics before the results arrive, then switch to ones that are more effective once the results are in.

If the kidney infection has advanced, you may need to stay at the hospital for bed rest. Your doctor will also want to give you fluids through an intravenous (IV) tube.

How to prevent a kidney infection

Reduce the risk of contracting the infection by practicing the following:

  • Drink a lot of water. Water flushes out bacteria following urination.
  • Urinate after sex. Urinating immediately after sex helps clear bacteria out of the urethra. This reduces the risk of infection.
  • Urinate immediately when the urge arises. Holding urine causes bacteria to multiply in the bladder, increasing the chances of infection.
  • Wipe yourself from front to back after using the toilet.

Failure to treat a urinary tract infection can cause serious health problems, including kidney infection, which in turn may end up damaging one or both your kidneys. If you’ve dealt with recurring urinary tract infections, visit your doctor more often for kidney checkups.

Health Solutions From Our Sponsors

Medically Reviewed on 4/14/2022
American Kidney Fund: "Kidney infection - Symptoms, treatment and prevention"

The Johns Hopkins University: "What is a kidney, ureter, and bladder X-ray?"

National Health Service: "Kidney infection."

National Institute of Diabetes and Digestive and Kidney Diseases: "Diagnosis of Kidney Infection (Pyelonephritis)", "Kidney Infection (Pyelonephritis)", "Treatment for Kidney Infection (Pyelonephritis)"

National Institute of Child Health and Development: "What causes UTIs & UI?"

National Kidney Foundation: "Infectious Disease and Your Kidneys"

The Nemours Foundation: "Urinary Tract Infections"

NephCure Kidney International: "What is the Function of Our Kidneys?"

Patient: "Kidney Infection (Pyelonephritis)"

Urology Care Foundation: "What is Kidney (Renal) Infection - Pyelonephritis?"