Kidney Infection

A kidney infection is a bacterial infection that has traveled up from the bladder into one or both kidneys. Kidney infection symptoms include fever, chills, and pain in the back or side. It needs antibiotics the same day to protect the kidneys.

What Is It

Doctors call it pyelonephritis. Most kidney infections start as a bladder infection, or UTI, that was not treated or did not clear. Women, pregnant women, older adults, and people with diabetes or kidney stones are at higher risk.

Symptoms

Fever and chills
Pain in the back, side, or groin, often on one side
Burning or pain when you pee
Needing to pee often or urgently
Cloudy, bloody, or foul smelling urine
Nausea or vomiting

Not sure it’s a kidney infection? A bladder infection, or UTI, causes burning and urgency, but usually no fever or back pain. Once fever, chills, or side pain appear, the infection may have reached the kidneys.

Treatment

At your visit: A urine test and checks of temperature, blood pressure, and hydration help confirm a kidney infection. Most are treated with antibiotic pills. Nausea medicine and IV fluids may help when you are dehydrated. A urine culture confirms the right antibiotic.

At home:

Take every dose of your antibiotic, even once you feel better
Drink plenty of water
Use a heating pad on low for back or side pain
Rest, and avoid alcohol and caffeine until you recover

Most people feel better within 2 to 3 days of starting antibiotics.

When to Get Care for a Kidney Infection

Watch at Home

Mild burning when you pee, with no fever or back pain
Symptoms improving on antibiotics you already started
You are drinking and keeping fluids down

Come to Urgent Care Today

Fever with burning or urgency when you pee
Pain in your back or side with urinary symptoms
A UTI that is not improving after 2 days of treatment
Nausea, but you can still keep fluids and pills down
Repeat UTIs, or a child with fever and urinary symptoms

Go to the Emergency Department

Vomiting that keeps you from keeping pills or fluids down
A fever above 103 degrees with shaking chills
Confusion, fainting, or a racing heart
Pregnancy with fever and back pain
Severe side pain with fever, which can mean a blocked, infected kidney

FAQ

What are the first signs of a kidney infection?

The first signs of a kidney infection are usually fever, chills, and pain in the back or side. Many people also have burning when they pee, urgency, or nausea.

How do I know if my UTI has spread to my kidneys?

A UTI has likely spread to the kidneys when fever, chills, nausea, or pain in the back or side appear. Bladder infections alone rarely cause fever or back pain.

Where is kidney infection pain located?

Kidney infection pain is usually felt in the back or side, just below the ribs, often on one side. It can spread to the lower belly or groin.

How long does a kidney infection take to heal?

A kidney infection usually improves within 2 to 3 days of starting antibiotics. The full course often lasts 7 to 14 days, and finishing it prevents the infection from coming back.

Can urgent care treat a kidney infection?

Yes, urgent care can treat most kidney infections. At Vitality Urgent Care, a provider can test your urine and check how sick you are. No appointment or referral is needed.

When is a kidney infection an emergency?

A kidney infection is an emergency when you cannot keep fluids or pills down, have shaking chills with a high fever, feel confused or faint, or are pregnant with fever.

Last reviewed October 2026