Skip to main content
Drug Info

Treating kidney infections with amoxicillin: Dosage, effectiveness, and side effects

Amoxicillin treats mild kidney infections, but alternative antibiotics may be required for more severe cases.
Rebecca Rovenstine writer headshot
By | Updated on Dec. 2, 2024 Medically reviewed by Jesse P. Houghton, MD, FACG
Rx pill bottle: Kidney infections & amoxicillin

Key takeaways

  • Kidney infections, known as pyelonephritis, happen when a lower urinary tract infection spreads upward from the bladder to the kidneys.

  • One possible course of treatment for kidney infections is the antibiotic amoxicillin.

  • Amoxicillin is typically prescribed for less severe kidney infections that are easily treated, but it can also be used at higher doses for pyelonephritis.

In this article:

A urinary tract infection (UTI) is a common bacterial infection with nearly 50 to 60% of women experiencing them in their lifetime. When a lower urinary tract infection spreads upward into the kidneys, it becomes a more serious condition called an upper urinary tract infection or kidney infection (pyelonephritis). Upon a diagnosis of a kidney infection from a healthcare provider, one of the most common treatments is oral antibiotics like amoxicillin.

Does amoxicillin treat a kidney infection? 

Amoxicillin can treat a kidney infection, but it’s not always the first line of defense. 

“[Amoxicillin] is usually chosen when the bacteria causing the infection are known to be sensitive,” explained Dr. Michael Genovese, a physician and Chief Medical Advisor at Ascendant New York. “Doctors often rely on antibiotics like ciprofloxacin or trimethoprim-sulfamethoxazole, which can be more effective in certain cases.”

The success rate of amoxicillin for kidney infection depends on the type of bacteria that caused the underlying infection. Different types of bacteria can cause the initial UTI that leads to a kidney infection. There are uncomplicated UTIs and complicated UTIs. If the bacteria is a stronger strain or antibiotic-resistant type, then the doctor may likely recommend something stronger than amoxicillin.

When seeking treatment for a suspected kidney infection, first the doctor will go over your medical history and symptoms. Common symptoms of pyelonephritis resemble UTI symptoms and include:

  • Fever
  • Chills
  • Tenderness or pain in your lower back or sides (flank pain)
  • Nausea or vomiting
  • Frequent urination that can be painful
  • Urine that is foul-smelling or cloudy
  • Blood in the urine

If you have these symptoms of a kidney infection, it’s vital to seek medical attention from a healthcare professional for a treatment plan. If the original bladder infection spreads into the kidneys and goes untreated, creating an even more severe infection, people can be at risk of kidney failure.

After reviewing your symptoms, diagnostic testing will be ordered so the doctor can best treat your infection. Urinalysis and urine culture are the most common tests to determine the presence of pyelonephritis, and they require a urine sample. For more complicated cases, a gram stain analysis may be performed to determine what bacteria is causing the infection. The most common bacteria causing acute pyelonephritis is Escherichia coli, more commonly known as E. coli.

Risk factors for developing a UTI include having recent sexual intercourse, underlying conditions in the urinary tract, a health history of recurrent UTIs, and poor hygiene, like children who have just become potty trained. Pregnant women, elderly patients, and those with a lowered immune system are also at higher risk.

For most people, a standard treatment option for a kidney infection is a course of antibiotics. This antibiotic treatment can last anywhere from 3 to 14 days.

Amoxicillin dosage for kidney infection

“Typically, the amoxicillin dosage for a kidney infection is 500 mg to 875 mg every 8 to 12 hours for adults,” said Dr. Genovese. He added, “However, the exact dose and duration should be tailored by a healthcare provider based on factors like the infection’s severity and other health considerations.”

This is higher than the dosage of amoxicillin given for UTIs, which typically ranges from 250 to 500 mg of amoxicillin every eight hours. 

There are several other commonly used antibiotics given for kidney infections. Amoxicillin and amoxicillin-clavulanate are part of the Penicillin group of antibiotics, but other groups of antibiotics, including cephalosporins, fluoroquinolones, aminoglycosides, and others, may be prescribed. Some of the most popular treatments for pyelonephritis include Bactrim, Ciprofloxin, and Septra.

How long after taking amoxicillin do kidney infection symptoms go away?

“Most patients who are symptomatic can find relief within 24 to 48 hours of starting antibiotics,” said Dr. Sean Devlin, the Chief Medical Officer of Brio-Medical in Scottsdale, Arizona. 

At home, be sure to drink plenty of fluids, which can help speed up recovery.

While amoxicillin begins reducing kidney infection symptoms within a day or two, it doesn’t mean you’re finished taking your medicine. It’s always important to finish a course of antibiotics, even if you feel fine, as the underlying bacteria can obtain antibiotic resistance, leading to further complications. According to Dr. Devlin, “Antibiotic courses can run from 3 to 14 days, depending on the patient and the infection.”

Sometimes, the symptoms of a kidney infection or UTI persist after a course of antibiotics. A study in 2021, which examined over 670,000 women, found that UTIs that aren’t cured with their first round of treatment are typically caused by inappropriate antibiotic agents or incorrect durations of treatment. If your symptoms linger after finishing antibiotics, it’s important to contact your healthcare provider for further medical treatment.

Disorders with similar symptoms also require different treatment. These can include interstitial cystitis and kidney stones. 

Side effects of amoxicillin for kidney infection

As with any medication, there are possible side effects associated with amoxicillin. One possible side effect of any antibiotic treatment is yeast infections and antibiotic-associated diarrhea, as antibiotics can also disturb the balance of healthy bacteria in your body.

Dr. Genovese explained, “Amoxicillin is generally well-tolerated, but it can have some mild side effects.” According to him, common side effects of amoxicillin can include:

  • Nausea
  • Diarrhea
  • Stomach upset
  • Skin rash

A skin rash can indicate an allergic reaction, but not in all cases—nevertheless, it should be monitored. Some patients may indeed have an allergic reaction to amoxicillin, which is characterized by itching, hives, throat swelling, or difficulty breathing  (anaphylaxis). If this happens, you should seek immediate medical attention.

“If you ever have concerns about side effects or feel your symptoms are not improving, do not hesitate to contact your healthcare provider for support,” advised Dr. Genovese.