A kidney infection requires antibiotics, and the sooner you start them, the better. Most people begin feeling noticeably improved within two to three days of their first dose, though a full course of antibiotics typically runs 7 days. Left untreated, a kidney infection can cause permanent kidney damage or allow bacteria to spread into the bloodstream, which can be life-threatening.
How Kidney Infections Are Treated
Antibiotics are the only effective treatment. A kidney infection (called pyelonephritis) is a bacterial infection, and no amount of fluids or rest will clear it without medication. Your provider will typically start you on an antibiotic right away, sometimes before your urine culture results come back, then adjust the prescription if needed once the lab identifies the exact bacteria involved.
Current guidelines from the Infectious Diseases Society of America recommend 7 days of antibiotic therapy for most kidney infections, a shift from the older standard of 10 to 14 days. If you’re prescribed a type of antibiotic called a fluoroquinolone, 5 to 7 days is often sufficient. The key condition is that you’re improving clinically on the medication. Regardless of the timeline, finish every pill. Stopping early raises the risk of the infection coming back or becoming harder to treat.
Outpatient vs. Hospital Treatment
Most uncomplicated kidney infections can be managed at home with oral antibiotics, as long as you can keep pills and fluids down and don’t show signs of a body-wide infection (sepsis). Many people are prescribed antibiotics in an urgent care or emergency department and sent home the same day.
Some situations require hospitalization. You’ll likely be admitted if you:
- Can’t tolerate oral medication due to severe nausea or vomiting
- Show signs of sepsis such as high fever, rapid heart rate, confusion, or very low blood pressure
- Have a urinary tract obstruction like a kidney stone blocking urine flow
- Are pregnant
- Have significant other health conditions such as diabetes, a weakened immune system, or sickle cell disease
- Haven’t improved after a round of outpatient antibiotics
In the hospital, antibiotics are given through an IV. Once you’re improving, able to eat and drink, and an effective oral antibiotic is available, guidelines support switching to pills for the rest of the treatment course rather than staying on IV therapy.
Managing Pain and Discomfort at Home
Kidney infections typically cause deep flank pain (the side of your back below the ribs), fever, chills, nausea, and painful urination. While antibiotics tackle the infection itself, you’ll want relief in the meantime.
Acetaminophen (Tylenol) is generally the safest choice for reducing fever and pain during a kidney infection. Common anti-inflammatory painkillers like ibuprofen and naproxen deserve caution. These can stress the kidneys, especially when you’re dehydrated, which is common during an infection with fever and reduced appetite. If you’re unsure what’s safe given your situation, ask your pharmacist or provider before taking anything.
A heating pad on your back or abdomen can help with flank pain. Keep the temperature moderate and limit sessions to 15 or 20 minutes at a time.
Hydration During Recovery
Drinking plenty of fluids helps flush bacteria from your urinary tract and supports your kidneys while they’re under stress. Aim for 8 to 12 glasses of fluid per day, with water being the best option. If you’re vomiting and can’t keep fluids down, that’s one of the reasons to seek emergency care, since dehydration during a kidney infection compounds the risk of kidney injury.
Recovery Timeline
Most people notice real improvement within two to three days of starting antibiotics. Fever usually breaks first, followed by gradual easing of back pain and urinary symptoms. Feeling fully back to normal can take one to two weeks, sometimes longer if the infection was severe or required hospitalization. Fatigue often lingers after the acute symptoms resolve.
Your provider may order a follow-up urine culture after you finish your antibiotics to confirm the infection has cleared. If bacteria are still present, you’ll need a second course of treatment, potentially with a different antibiotic.
Kidney Infections During Pregnancy
Pregnancy raises the stakes considerably. A kidney infection during pregnancy increases the risk of preterm birth, low birth weight, anemia, sepsis, and other serious complications for both the mother and baby. Pregnant individuals with a kidney infection are almost always hospitalized for IV antibiotics and monitoring.
The antibiotics used during pregnancy are chosen for fetal safety. First-line options are typically broad-spectrum penicillin-type drugs or certain injectable antibiotics. If you have a penicillin allergy, your provider will assess the severity of your allergy history before selecting an alternative. Even a simple bladder infection during pregnancy warrants prompt treatment, because each episode of lower urinary tract infection risks progressing to a kidney infection.
Why Treatment Differs for Men
Kidney infections are less common in men, but when they happen, treatment can take longer. The prostate gland sits at the base of the bladder, and bacteria from a urinary tract infection can settle into prostate tissue, where antibiotics have a harder time penetrating. If a prostate infection is suspected alongside or instead of a kidney infection, antibiotic courses often extend to 4 to 6 weeks, sometimes longer.
What Happens if Treatment Is Delayed
An untreated kidney infection doesn’t resolve on its own. Bacteria continue multiplying, and the infection can progress in two dangerous directions. First, it can cause lasting damage to the kidney itself, including scarring that reduces the organ’s ability to filter waste. Second, bacteria can enter the bloodstream, leading to sepsis, a condition where the body’s response to infection starts damaging its own tissues. Severe sepsis can cause organ failure and death.
An abscess, a walled-off pocket of pus inside or around the kidney, is another possible complication. Abscesses sometimes require drainage in addition to antibiotics. People with diabetes, kidney stones, or structural abnormalities in the urinary tract face higher risks for these complications, making early treatment especially important.