A kidney infection is treated with antibiotics, typically for 5 to 14 days depending on the type prescribed. Most uncomplicated cases can be managed at home with oral antibiotics, fluids, and rest. Because kidney infections can cause permanent kidney damage or spread bacteria into the bloodstream if left untreated, prompt treatment matters more here than with a simple bladder infection.
How Kidney Infections Are Diagnosed
If you go in with symptoms like flank pain, fever, chills, nausea, or painful urination, your doctor will typically start with a urinalysis. This checks your urine for white blood cells (a sign your body is fighting a bacterial infection) and blood, both of which point toward a kidney infection. A urine culture may also be ordered to identify the specific bacteria causing the infection, which helps determine which antibiotic will work best.
Most kidney infections start as bladder infections that travel upward. The bacteria responsible are almost always from the digestive tract, with E. coli being the most common culprit by a wide margin. Less frequently, bacteria like Proteus or Klebsiella species are involved.
Antibiotic Treatment
For uncomplicated kidney infections in women, the standard first-line oral antibiotics are fluoroquinolones (such as ciprofloxacin for 7 days or levofloxacin for 5 days) or trimethoprim/sulfamethoxazole for 14 days. Clinical trials involving over 2,500 patients have shown that a 5-to-7-day course of fluoroquinolones works just as well as a 14-day course, so shorter regimens are common when the bacteria are susceptible.
Not every antibiotic that works for a bladder infection works for a kidney infection. Nitrofurantoin and fosfomycin, two medications frequently prescribed for simple UTIs, don’t reach high enough concentrations in kidney tissue to be effective here. Some penicillin-type antibiotics are also considered inferior for kidney infections and aren’t recommended as first-line options.
Your doctor may start you on antibiotics before your urine culture results come back, then adjust if needed once the lab identifies the exact bacteria and which drugs it responds to. Take the full course even if you start feeling better within a couple of days. Stopping early increases the risk of the infection returning or becoming harder to treat.
When Hospital Treatment Is Needed
Most people recover at home, but some cases require hospital admission for intravenous antibiotics. This is more likely if you’re pregnant, have a chronic health condition that weakens your immune system, can’t keep fluids or oral medication down due to vomiting, or aren’t improving after a couple of days on oral antibiotics. IV antibiotics work faster and deliver the medication more reliably when oral treatment isn’t cutting it.
If you develop a high fever that won’t come down, severe back or side pain, confusion, or signs of dehydration like very dark urine or dizziness, those are signals the infection may be worsening. Untreated or poorly treated kidney infections can lead to permanent kidney damage or allow bacteria to enter the bloodstream, which is a medical emergency.
Managing Pain and Symptoms at Home
While antibiotics fight the infection, you’ll likely need something for the pain. Acetaminophen (Tylenol) is generally the safer choice during a kidney infection. Ibuprofen and other anti-inflammatory painkillers are processed by the kidneys, and taking them while your kidneys are already under stress from an infection can increase the risk of kidney damage. If you’re unsure which pain reliever to use, acetaminophen at standard doses (up to 3,000 milligrams per day for adults) is a reasonable default.
Staying well-hydrated helps flush bacteria from your urinary tract and supports kidney function during recovery. Water is ideal. A heating pad on your back or abdomen can also help with the deep, aching flank pain that kidney infections are known for.
What Recovery Looks Like
You should start feeling noticeably better within 48 to 72 hours of starting antibiotics. Fever typically drops first, followed by a gradual easing of back pain and urinary symptoms over the next several days. If you’re not improving within two to three days, contact your doctor. You may need a different antibiotic, a longer course, or further testing to check for complications like a kidney abscess or a structural blockage that’s preventing the infection from clearing.
Even after symptoms resolve, mild fatigue can linger for a week or two. This is normal. Your body has been fighting a significant infection, and full recovery takes time. Finish your entire antibiotic course regardless of how you feel.
Kidney Infections During Pregnancy
Kidney infections in pregnancy are treated more aggressively because the stakes are higher for both the pregnant person and the baby. Hospitalization for IV antibiotics is more common, and the total treatment course is typically 14 days. Once a patient is clinically improving on IV antibiotics, they can usually switch to oral medication to finish the course at home.
Antibiotic choices differ during pregnancy. Ampicillin and amoxicillin are generally avoided because E. coli has developed high resistance to them in most regions. Nitrofurantoin and fosfomycin, while sometimes used for simple bladder infections in pregnancy, are not appropriate for kidney infections because they can’t reach effective levels in kidney tissue. Your doctor will choose an antibiotic based on your urine culture results and what’s safe for your stage of pregnancy.
After a kidney infection during pregnancy, your provider may recommend a low daily dose of a preventive antibiotic for the remainder of the pregnancy to keep the infection from coming back. Recurrence is common in pregnancy due to the physical changes that make it easier for bacteria to travel from the bladder to the kidneys.
Preventing Recurrence
Kidney infections almost always start as lower urinary tract infections that weren’t caught or treated in time. The most effective prevention is treating bladder infections early, before bacteria have a chance to climb to the kidneys. If you notice burning with urination, frequent urges to go, or cloudy urine, getting a urine test sooner rather than later can prevent a much more serious problem.
General habits that reduce UTI risk also reduce kidney infection risk: staying hydrated, urinating after sex, wiping front to back, and avoiding holding your urine for extended periods. If you get recurrent UTIs, talk to your doctor about whether a preventive strategy, like a low-dose daily antibiotic or post-sex prophylaxis, makes sense for you.