Doctors prescribe antibiotics to treat kidney infections, with the specific drug depending on local resistance patterns and your urine culture results. Most people with an uncomplicated kidney infection take oral antibiotics at home for 5 to 14 days, and the infection clears without complications. The most commonly prescribed options include fluoroquinolones, sulfamethoxazole-trimethoprim, and several types of cephalosporins.
How Doctors Choose Your Antibiotic
Before prescribing anything, your doctor will typically order a urine culture. This test identifies which bacterium is causing the infection and which antibiotics it responds to. The vast majority of kidney infections are caused by E. coli, the same bacterium behind most bladder infections. While you wait for culture results (usually 48 to 72 hours), your doctor will start you on an antibiotic chosen based on what works best against common bacteria in your area.
That local context matters more than you might expect. Bacteria in different regions have developed resistance to different drugs. If fewer than 10% of local E. coli strains resist fluoroquinolones, those are typically the go-to choice. In areas where resistance runs higher, doctors shift to alternatives like amoxicillin-clavulanate or cephalosporins. Once your culture results come back, your doctor may switch you to a more targeted antibiotic if the first one isn’t the best match.
The Most Common Prescriptions
Fluoroquinolones (such as ciprofloxacin and levofloxacin) are the preferred first-line option when local resistance allows. They’re effective against most strains of E. coli, penetrate kidney tissue well, and require a shorter course: typically 5 to 7 days. For men, doctors often extend this to 14 days.
When fluoroquinolones aren’t appropriate, the main alternatives include:
- Sulfamethoxazole-trimethoprim (Bactrim, Septra): A well-established combination antibiotic, taken for 10 to 14 days. Growing bacterial resistance has made it less reliable as a first guess, but it works well when cultures confirm the bacterium is sensitive to it.
- Amoxicillin-clavulanate (Augmentin): Taken twice daily for 7 to 10 days. This pairs a common penicillin-type antibiotic with a compound that helps it overcome certain resistant bacteria.
- Cephalosporins (cefpodoxime, cefadroxil, cephalexin): Taken twice daily for 7 to 10 days. These are broad-spectrum antibiotics that work against a wide range of bacteria causing kidney infections.
Your doctor picks among these based on your allergy history, your culture results, and what’s been working in your community. There’s no single “best” antibiotic for everyone.
How Long Treatment Lasts
Kidney infections require longer antibiotic courses than simple bladder infections. While a bladder infection might clear in 3 to 5 days, kidney infections typically need 5 to 14 days depending on the drug. Fluoroquinolones work in 5 to 7 days. Sulfamethoxazole-trimethoprim and oral cephalosporins generally need 10 to 14 days to fully clear the infection.
You’ll likely start feeling better within 2 to 3 days, but finishing the entire course is critical. Stopping early can leave surviving bacteria behind, leading to a relapse that’s harder to treat the second time around.
Pain Relief Alongside Antibiotics
Kidney infections can cause significant flank pain, fever, and general misery while the antibiotics take hold. Over-the-counter pain relievers like ibuprofen or acetaminophen are commonly recommended to manage pain and bring down fever during the first few days. Staying well hydrated also helps your body flush bacteria from the urinary tract and can reduce some of the discomfort.
Most people notice the worst symptoms, particularly fever and the deep ache in the lower back or side, easing substantially within 48 to 72 hours of starting antibiotics.
When Treatment Happens in a Hospital
Not every kidney infection can be managed at home with pills. If you can’t keep fluids or oral medication down because of severe nausea and vomiting, or if you have a high fever with signs of the infection spreading to the bloodstream, doctors will admit you for intravenous antibiotics. Pregnant individuals, people with diabetes, and those with a weakened immune system are also more likely to need hospital-based treatment because of the higher risk of complications.
Hospital stays for kidney infections are usually short. Once the fever breaks and you’re able to eat and drink normally, doctors typically switch you to oral antibiotics and send you home to complete the rest of your course there.
Kidney Infections During Pregnancy
Pregnancy changes the equation significantly. Certain antibiotics that work well for kidney infections in the general population aren’t safe during pregnancy, and the infection itself carries greater risks, including preterm labor. Doctors rely primarily on penicillin-type antibiotics and cephalosporins, which have well-established safety profiles for pregnant individuals.
Two antibiotics commonly used for bladder infections, nitrofurantoin and fosfomycin, are specifically avoided when a kidney infection is suspected or confirmed. Neither reaches adequate levels in kidney tissue, so they can’t effectively treat the infection even though they work well in the bladder. Because kidney infections during pregnancy tend to progress quickly, treatment is more aggressive from the start, and many pregnant patients receive at least an initial course of intravenous antibiotics.
Treatment for Children
Children with kidney infections are treated with the same classes of antibiotics as adults, but at doses based on their weight. Common options for kids include sulfamethoxazole-trimethoprim, amoxicillin-clavulanate, and several cephalosporins (cefixime, cefpodoxime, cephalexin). Courses run 7 to 14 days for young children. As with adults, the choice depends on local resistance patterns and culture results.
What Happens If Symptoms Don’t Improve
If your symptoms haven’t improved noticeably within 2 to 3 days of starting antibiotics, your doctor will reassess. The most common reason is that the bacterium causing your infection is resistant to the antibiotic you were started on. Your urine culture results, which are usually back by then, will show exactly which drugs the bacteria respond to, and your doctor can switch accordingly.
In some cases, persistent symptoms signal a complication like a kidney abscess or a blockage in the urinary tract that’s preventing the infection from draining. Imaging, usually an ultrasound or CT scan, helps identify these problems. Recurrent kidney infections within a few weeks of finishing treatment also warrant a repeat urine culture and possibly imaging to look for an underlying structural issue.
Follow-Up After Treatment
If your symptoms fully resolve by the end of your antibiotic course, you generally don’t need a follow-up urine test. Routine “test of cure” cultures aren’t recommended for people who feel better. However, if symptoms return within two weeks of finishing treatment, or if they never fully resolved, a repeat urine culture is important to guide next steps. This helps determine whether you’re dealing with a relapse of the same infection or a new one, which changes the treatment approach.