A kidney infection requires antibiotics, and the sooner you start them, the better. Unlike a simple bladder infection that sometimes resolves on its own, a kidney infection (pyelonephritis) can become dangerous without treatment. Most people feel noticeably better within a few days of starting antibiotics, though full recovery typically takes about two weeks.
Recognizing a Kidney Infection
Kidney infections usually start as a lower urinary tract infection that travels upward. The symptoms go beyond the burning and frequency of a typical bladder infection. You’ll likely have pain in your back or side, fever and chills, nausea or vomiting, and urine that looks cloudy or smells unusual. The flank pain is a key distinguishing feature: it’s a deep ache on one or both sides of your lower back, near where your kidneys sit.
To confirm a kidney infection, your doctor will typically order a urinalysis to check for white blood cells and blood in the urine, along with a urine culture to identify the specific bacteria causing the infection. Blood tests may be ordered to assess how well your kidneys are functioning and to check for signs that the infection has spread. In some cases, imaging like an ultrasound or CT scan is used to look for complications such as a blockage or abscess.
How Antibiotics Work for Kidney Infections
Oral antibiotics are the standard treatment. Current guidelines from the Infectious Diseases Society of America recommend a shorter course than was traditionally prescribed: 5 to 7 days for certain antibiotic classes, or 7 days for others, rather than the 10 to 14 days that used to be standard. This applies to people who are responding well to treatment and improving clinically. Your doctor chooses the specific antibiotic based on the bacteria identified in your urine culture, local resistance patterns, and your individual health profile.
Finish the entire course of antibiotics even if you start feeling better after a couple of days. Stopping early can leave surviving bacteria in your kidneys, setting you up for a harder-to-treat recurrence.
Some people need treatment in a hospital, at least initially. If you can’t keep fluids or pills down due to vomiting, you’ll receive antibiotics and fluids through an IV. Once you’re improving and tolerating oral medication, you’ll typically switch to pills and go home. People with underlying conditions, weakened immune systems, urinary blockages, or kidney abscesses may need longer or more intensive treatment.
Managing Pain at Home
Acetaminophen (Tylenol) is generally the safest choice for pain and fever during a kidney infection. It’s effective and doesn’t affect blood flow to the kidneys.
NSAIDs like ibuprofen (Advil, Motrin) and naproxen (Aleve) are a different story. These drugs reduce blood flow through the kidneys, which can lead to acute kidney injury, particularly when your kidneys are already under stress from an infection. If you have any degree of reduced kidney function, high blood pressure, or heart disease, NSAIDs carry even more risk. Stick with acetaminophen unless your doctor specifically tells you otherwise.
A heating pad on your back or side can also help ease flank pain. Keep it on a low setting and limit sessions to 15 or 20 minutes at a time.
Hydration and Rest
Drinking plenty of fluids, especially water, helps flush bacteria from your urinary tract and supports recovery. There’s no magic number of glasses per day, but aim to drink enough that your urine stays pale yellow. If you’re running a fever or vomiting, you’ll need more fluids than usual to stay hydrated.
Rest matters more than people expect. A kidney infection is a systemic illness, not just a local nuisance. Plan on feeling fatigued for up to two weeks, and don’t push yourself back to work or full activity before you’re ready. Older adults and people with chronic health conditions often take longer to bounce back.
Warning Signs That Need Emergency Care
A kidney infection can, in rare cases, progress to sepsis, a life-threatening response to infection spreading through the bloodstream. Get to an emergency room if you experience any of the following:
- Confusion or disorientation
- Rapid breathing or heart rate
- Shortness of breath
- Severe pain that isn’t controlled by medication
- High fever with shaking chills
- Inability to keep fluids down
These symptoms suggest the infection may be overwhelming your body’s ability to contain it. Sepsis requires IV antibiotics and close monitoring in a hospital.
What Recovery Actually Looks Like
Most people notice their fever dropping and pain easing within the first two to three days of antibiotics. That improvement can feel dramatic, which is exactly why it’s tempting to stop medication early. Resist that impulse. The bacteria causing the infection can persist even after symptoms fade.
Full recovery, meaning you feel like yourself again with normal energy levels, typically takes about two weeks. During that time, you may still feel more tired than usual, have mild back discomfort, or notice changes in your urine. These are normal parts of healing. If your symptoms aren’t improving after 48 to 72 hours on antibiotics, or if they get worse at any point, contact your doctor. The bacteria causing your infection may be resistant to the antibiotic you were prescribed, and a switch may be needed.
Preventing Future Kidney Infections
Most kidney infections start as bladder infections that climb the urinary tract. Reducing your risk of bladder infections is the best way to prevent kidney infections from happening again.
- Stay hydrated. Water helps flush bacteria from your urinary tract before they can establish an infection.
- Urinate regularly. Don’t hold it for long periods. A full bladder gives bacteria more time to multiply.
- Urinate after sex. Sexual activity can push bacteria toward the urethra. Urinating shortly afterward helps clear them out.
- Wipe front to back. This prevents bacteria from the anal area from reaching the urethra.
- Avoid spermicide and diaphragms. These can disrupt the natural bacterial balance and increase UTI risk. Condoms or other birth control methods are better options.
For people who get recurrent UTIs, doctors sometimes prescribe low-dose antibiotics taken daily for several months or a single dose after sexual activity. Cranberry extract supplements may offer modest protection by making it harder for certain bacteria to latch onto the bladder wall, though they’re not a substitute for antibiotics when an infection is already present.
People going through perimenopause or postmenopause face a higher risk of recurrent UTIs because declining estrogen levels change the vaginal environment. Vaginal estrogen, applied as a cream, tablet, or ring, restores acidity and helps prevent infections from taking hold. It’s one of the most effective interventions for postmenopausal people with recurring UTIs.