Kidney Infection: A Comprehensive Guide
Medically reviewed by Andre Stone | MD, University of Pittsburgh School of Medicine on August 25th, 2026.
Published on April 5th, 2026. Updated on September 28th, 2026.
Key Takeaways
Kidney infections are serious bacterial infections that need prompt medical treatment
Women are more likely to develop kidney infections than men
Common symptoms include fever, back pain, and painful urination
Untreated kidney infections can lead to permanent kidney damage or blood poisoning
Most kidney infections start as bladder infections that spread upward
Overview
A kidney infection, also called pyelonephritis, is a serious bacterial infection that affects one or both kidneys. This condition occurs when bacteria travel from your bladder up through the tubes that connect your bladder to your kidneys. While kidney infections can happen to anyone, they're more common in women due to their anatomy.
Kidney infections are relatively common, especially in women, but estimates vary by population and healthcare setting. They're much more serious than simple bladder infections and can cause permanent kidney damage if not treated quickly. The good news is that with proper antibiotic treatment, most people recover completely.
This condition matters because your kidneys filter waste from your blood and make urine. A kidney infection can affect kidney function, especially if the infection is severe or complicated. Quick treatment lowers the risk of serious complications, including sepsis and, in some cases, kidney damage.
Your kidneys are bean-shaped organs that sit on both sides of your spine. They clean your blood by removing extra water and waste to make urine. Without healthy kidneys, harmful waste builds up in your body and can make you very sick.
Symptoms & Signs
Kidney infection symptoms often develop quickly, sometimes within hours. The signs can be intense and different from a regular bladder infection.
Primary Symptoms
High fever (usually above 101°F) with chills and shaking
Severe back or side pain, especially around your ribs
Burning sensation or pain when urinating
Frequent, urgent need to urinate
Cloudy, bloody, or foul-smelling urine
Nausea and vomiting
General feeling of being very sick
Some people also experience muscle aches and feel confused or disoriented. You might notice that your urine looks dark or has a strong smell. Some patients feel so sick they can't eat or drink anything.
When to Seek Care
You should get medical help right away if you have fever with back pain and urinary symptoms. Don't wait if you're vomiting and can't keep fluids down. Severe symptoms that get worse quickly need immediate attention.
If your fever is very high or your pain is unbearable, go to an emergency room. Call 911 if you feel dizzy, faint, or have trouble breathing. These symptoms can be signs of a serious infection or another emergency and need urgent medical assessment.
When to Seek Immediate Care
Urgent care facilities can often evaluate and treat a suspected kidney infection. Go to an emergency room or call 911 for the severe symptoms described above. Can urgent care diagnose a kidney infection? These facilities can often provide quick diagnosis and treatment.
Causes & Risk Factors
Most kidney infections start when bacteria enter your urinary system through your urethra and multiply in your bladder. The bacteria then travel up to one or both kidneys. The most common bacteria that cause kidney infections is E. coli, which normally lives in your bowel.
Sometimes kidney infections develop when bacteria from other parts of your body travel through your bloodstream to your kidneys. This is less common but can happen if you have a bloodstream infection.
Bacteria usually can't reach your kidneys because your body has defenses to stop them. But sometimes these defenses don't work well, and bacteria get through. Things like kidney stones or an enlarged prostate can block urine flow and let bacteria grow.
Age
Young children and adults over 60 have higher risk
Genetics
Family history of urinary tract infections increases risk
Lifestyle
Urinary tract problems that interfere with bladder emptying and sexual activity can increase risk in some people.
Other Conditions
Diabetes, kidney stones, enlarged prostate, pregnancy
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Diagnosis
Getting the right diagnosis quickly is important for kidney infections. Your doctor will ask about your symptoms and examine you to determine if you have this serious condition.
Medical History & Physical Examination
Your doctor will ask about your symptoms, when they started, and how severe they are. They'll want to know if you've had urinary tract infections before. During the physical exam, your doctor will check your temperature and gently press on your back and sides to see if your kidneys are tender. They may also examine your abdomen and check for other signs of infection.
Diagnostic Testing
Urine test to check for bacteria, white blood cells, and red blood cells
Urine culture to identify the specific bacteria causing the infection
Blood tests to check for signs of infection and kidney function
CT scan or ultrasound if complications are suspected
Blood culture if sepsis is a concern
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Treatment Options
The main goal of kidney infection treatment is to eliminate the bacteria and prevent complications. Most people need antibiotic treatment right away.
Conservative Treatments
Mild infections may be treated with oral antibiotics. The antibiotic and treatment length depend on the medicine used, test results, and the patient's circumstances.
Drink enough fluids to avoid dehydration unless a healthcare professional has advised you to limit fluids.
Ask a healthcare professional which pain reliever is safe for you. Acetaminophen may be appropriate for many people, while ibuprofen may not be suitable if you are dehydrated, have kidney problems, are pregnant, or take certain medicines.
Rest to help your body fight the infection
Advanced Treatments
IV antibiotics in the hospital for severe infections or if you can't keep oral medications down
Hospitalization if you're very sick, dehydrated, or have complications
Surgery to drain abscesses or remove kidney stones if they're blocking urine flow
Treatment of underlying conditions that increase infection risk
Starting antibiotics quickly is the most important part of treatment. Treatment often starts before culture results are available. Your doctor may adjust the antibiotic after urine culture results identify the bacteria and which medicines are likely to work. Most people start feeling better within 24 to 48 hours after starting antibiotics.
Living with the Condition
While you're recovering from a kidney infection, there are several things you can do to help your body heal and prevent future infections. Taking care of yourself during treatment is important for a full recovery.
Taking your antibiotics exactly as prescribed is crucial, even if you start feeling better. Drink plenty of water to help flush bacteria from your system. Rest when you need to, as your body uses energy to fight the infection.
Stopping antibiotics earlier than prescribed can allow the infection to return or remain incompletely treated.
Daily Management Strategies
Drink enough fluids to avoid dehydration unless a healthcare professional has told you to limit fluids. Ask for advice if you have kidney or heart problems or cannot keep fluids down. Urinate frequently and completely empty your bladder each time. Wipe from front to back after using the bathroom. Take warm baths to help ease back pain, but avoid bubble baths that can irritate.
Exercise & Movement
Light walking is okay if you feel up to it, but avoid strenuous activity while you have fever, pain, weakness, or dehydration and until you feel well enough to resume it. Listen to your body and rest when you feel tired or weak.
Follow up as your healthcare professional recommends. Contact them promptly if symptoms do not begin improving within a few days, worsen, or return. Repeat urine testing may be needed in pregnancy or other higher-risk situations but is not routine for everyone who recovers.
Prevention
Drink enough water to avoid dehydration unless a healthcare professional has advised you to limit fluids.
Urinate soon after sexual activity to help eliminate bacteria
Wipe from front to back after using the bathroom to prevent bacterial spread
Don't hold your urine for long periods - empty your bladder when you feel the urge
Avoid products that irritate the genital area.
Choose underwear and clothing that feel comfortable and do not cause irritation.
Treat bladder infections promptly before they spread to your kidneys
Getting early treatment for bladder infections is one of the best ways to prevent kidney infections. Watch for symptoms like burning when you urinate or feeling like you need to go more often. See a doctor right away if you think you have a bladder infection.
Women should be extra careful because they get kidney infections more often than men. This is because women's urethras are shorter, making it easier for bacteria to travel to the bladder and kidneys. Seek prompt care for urinary symptoms and ask a healthcare professional about prevention if infections keep recurring.
Keep your blood sugar under control if you have diabetes, as high blood sugar increases infection risk. Stay hydrated by drinking water throughout the day. Avoid holding your urine and empty your bladder completely when you go.
Frequently Asked Questions
Most people start feeling better within 24-48 hours of starting antibiotics. Complete recovery usually takes 1-2 weeks with proper treatment. Hospital safety measures are important if hospitalization is needed.
Untreated kidney infections can cause serious complications, including sepsis and, in some cases, kidney scarring or lasting kidney damage. Kidney failure is uncommon but may occur with severe or complicated infection. This is why it's so important to get treatment quickly when symptoms develop.
No, you can't catch a kidney infection directly from another person. Kidney infections are not sexually transmitted. Sexual activity can move bacteria already present around the genital and anal area toward the urethra, which may increase the risk of a urinary tract infection in some people. Urinating after sex is commonly suggested, although evidence that it prevents infection is limited.
Bladder infections typically cause urinary symptoms without fever. Kidney infections cause fever, back pain, and make you feel much sicker overall. Kidney infections are more serious and need immediate treatment.
Yes, pregnant women have a higher risk of kidney infections due to changes in their urinary system. Treating infections during pregnancy requires special consideration for both mother and baby's safety.
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