Kidney Infection Symptoms
Urological HealthKidney Infection

Symptoms of a Kidney Infection

Symptoms of a Kidney Infection
Everyday Health
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Updated on January 12, 2026
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A kidney infection, also known as pyelonephritis, usually develops when bacteria from a urinary tract infection (UTI) travel from your bladder through the tubes, called ureters, that connect your bladder to your kidneys.

When your kidneys become infected, a number of symptoms can occur. Some of these symptoms occur around the area of the infection, while others affect your whole body.

It’s important to recognize the symptoms of a kidney infection so you can receive a diagnosis and treatment from a healthcare professional. If left untreated, a kidney infection can cause serious complications.

medical graphic on How Kidney Infection Affects the Body, man centered surrounded by symptoms including confusion, abdominal pain, painful urination, cloudy or discolored urine, frequent urination, nausea or vomiting, lower back pain, pelvic pain, fever
A kidney infection can cause any of these symptoms.Everyday Health

Symptoms of a Kidney Infection

Typically, a kidney infection develops after a UTI has already affected your bladder and urethra (the tube through which urine exits your body). This area is known as your lower urinary tract.

If you recognize the earlier symptoms of a UTI, you can seek treatment and usually avoid a kidney infection. But it’s possible that your symptoms won’t be severe enough to get your attention until the infection has spread to your kidneys.

Whether or not you’re also experiencing kidney-specific symptoms, it’s important to look for signs of a UTI affecting your lower urinary tract:

  • Painful urination (dysuria)
  • Frequent urination
  • Urge to go frequently, even with an empty bladder
When you have a UTI that spreads to your kidneys, you’ll probably have symptoms in your lower urinary tract first. But the following symptoms indicate that your kidneys may also be affected:

  • Fever and chills
  • Pain in your lower back or side
  • Nausea and vomiting
  • Abdominal or pelvic pain
  • Cloudy or smelly urine (though this alone does not necessarily signal a kidney infection)
  • Dark or bloody urine

Symptoms in Children and Elderly People

While the typical range of symptoms for a kidney infection applies to most adults, older adults and young children may have different symptoms.

Older adults may experience none of the typical symptoms of a kidney infection summarized above. Instead, they may experience cognitive symptoms. Research shows that UTIs are linked to delirium in people over 65 years old.

Children under 2 years old with a kidney infection may only have a high fever.

Caregivers of very old and very young individuals should know to seek help when these symptoms occur.

Kidney Infection Complications

Most kidney infections don’t usually cause complications when they’re diagnosed and treated. In rare cases, however, they can cause the following complications:

  • Kidney failure
  • Kidney scarring, a precursor to chronic kidney disease
  • High blood pressure
  • Sepsis

The chances of complications are slightly higher if you are any of the following:

  • Male
  • Older
  • Pregnant

Additionally, the risk of complications can also be greater if you have:

  • A structural problem with your urinary tract
  • Had repeat kidney infections
  • Certain health conditions, like diabetes or kidney disease
  • A weakened immune system
  • Had an organ transplant

When to See a Doctor

If you experience any symptoms of a kidney infection or a UTI, it’s important to see a healthcare professional to be evaluated right away.

This is true especially if certain symptoms seem to appear suddenly, indicating that your UTI is spreading or growing more quickly.

A kidney infection that isn’t treated effectively can become chronic (long-lasting), potentially causing permanent damage to your kidneys and impairing their function.

An untreated kidney infection can also lead to dangerous complications in the short term, such as a blood infection (sepsis).

Symptoms of sepsis include:

  • Fever and chills
  • Rapid breathing
  • Elevated heart rate
  • Skin rash
  • Profound weakness or lethargy
  • Confusion

The Takeaway

  • A kidney infection often starts as a urinary tract infection (UTI), so pay attention to any early symptoms of a UTI to prevent it from spreading to your kidneys.
  • Symptoms of a kidney infection include painful or frequent urination, changes in the color or smell of your urine, fever, nausea or vomiting, and pain in the lower back, abdominal, or pelvic area.
  • In younger children and older adults, a UTI or kidney infection can present differently, such as causing a fever or changes in cognition.
  • As soon as you recognize the symptoms, see a healthcare professional for treatment and to prevent complications.

Resources We Trust

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Kidney Infection (Pyelonephritis). National Institute of Diabetes and Digestive and Kidney Diseases. October 2024.
  2. Bladder Infection (Urinary Tract Infection — UTI) in Adults. National Institute of Diabetes and Digestive and Kidney Diseases. April 2024.
  3. Urinary Tract Infection (UTI). Mayo Clinic. September 26, 2025.
  4. Dutta C et al. Urinary Tract Infection Induced Delirium in Elderly Patients: A Systematic Review. Cureus. December 8, 2022.
  5. Weinberg GA. Urinary Tract Infection (UTI) in Children. Merck Manual. October 2025.
  6. Definition & Facts of Kidney Infection (Pyelonephritis). National Institute of Diabetes and Digestive and Kidney Diseases. October 2024.
  7. Melia M. Pyelonephritis, Acute, Uncomplicated. Johns Hopkins Medicine. June 10, 2024.
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Igor Kagan, MD

Medical Reviewer
Castle Connolly Top Doctor

Igor Kagan, MD, is an an assistant clinical professor at UCLA. He spends the majority of his time seeing patients in various settings, such as outpatient clinics, inpatient rounds, and dialysis units. He is also the associate program director for the General Nephrology Fellowship and teaches medical students, residents, and fellows. His clinical interests include general nephrology, chronic kidney disease, dialysis (home and in-center), hypertension, and glomerulonephritis, among others. He is also interested in electronic medical record optimization and services as a physician informaticist.

A native of Los Angeles, he graduated cum laude from the University of California in Los Angeles (UCLA) with a bachelor's in business and economics, and was inducted into the Phi Beta Kappa honor society. He then went to the Keck School of Medicine at the University of Southern California (USC) for his medical school education. He stayed at USC for his training and completed his internship and internal medicine residency at the historic Los Angeles County and USC General Hospital. Following his internal medicine residency, Kagan went across town to UCLA's David Geffen School of Medicine for his fellowship in nephrology and training at the UCLA Ronald Reagan Medical Center. After his fellowship he stayed on as faculty at UCLA Health.

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Quinn Phillips

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A freelance health writer and editor based in Wisconsin, Quinn Phillips has a degree in government from Harvard University. He writes on a variety of topics, but is especially interested in the intersection of health and public policy. Phillips has written for various publications and websites, such as Diabetes Self-Management, Practical Diabetology, and Gluten-Free Living, among others.

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