Amoxicillin treats some bacterial infections, but it is not usually the first choice for a kidney infection unless testing shows that the bacteria are susceptible to it.
Amoxicillin is a penicillin antibiotic used to treat certain bacterial infections. However, its effectiveness against a kidney infection depends on the bacteria responsible and whether they are resistant to the medicine.
A kidney infection, medically known as pyelonephritis, is a type of urinary tract infection (UTI) that affects one or both kidneys. It often develops when bacteria spread from the bladder to the kidneys. Without prompt treatment, the infection can cause serious complications.
When is amoxicillin appropriate for a kidney infection?
Amoxicillin may be prescribed in selected cases if laboratory testing shows that the bacteria causing the infection are susceptible to it. However, resistance to amoxicillin is common among bacteria responsible for urinary tract infections, which limits its usefulness as an initial treatment when the cause has not been identified.
The National Institute for Health and Care Excellence (NICE), which publishes clinical guidelines in the United Kingdom, recommends selecting antibiotics for acute kidney infections according to factors including bacterial susceptibility, local resistance patterns, the severity of the infection and the patient’s medical circumstances.
Doctors may request a urine culture, a laboratory test that identifies bacteria growing in a urine sample and helps determine which antibiotics are likely to work. Treatment can then be adjusted if the results show that the initial antibiotic is unsuitable.
Amoxicillin should not be taken for a suspected kidney infection without medical advice. Anyone experiencing symptoms should seek prompt assessment rather than waiting for the infection to worsen.
What causes a kidney infection?
Most kidney infections are caused by bacteria entering the urinary tract and travelling from the bladder to one or both kidneys. Escherichia coli (E. coli), a bacterium commonly found in the intestines, is the most frequent cause.
Other bacteria can also cause the infection. The likelihood of developing a kidney infection may increase when urine cannot drain normally, when the urinary tract has structural abnormalities, or when the body’s immune defences are weakened. Kidney stones and the use of urinary catheters can also increase the risk.
A kidney infection is not the same as a bladder infection. Although the two conditions can share symptoms, a kidney infection affects the upper urinary tract and can become more serious if treatment is delayed.
Symptoms of a kidney infection
Symptoms vary between individuals, but common signs include:
- Fever and chills.
- Pain in the back, side or groin.
- Pain or a burning sensation when urinating.
- Frequent or urgent urination.
- Nausea and vomiting.
- Cloudy, dark, bloody or unusually strong-smelling urine.
Some people may also feel generally unwell or experience weakness and fatigue. However, symptoms alone cannot confirm that someone has a kidney infection.
The NIDDK advises people with symptoms of a kidney infection to seek medical care promptly because the condition can, in some cases, lead to sepsis, a serious response to infection that can cause organ damage.
How is a kidney infection diagnosed?
A healthcare professional will assess the patient’s symptoms and medical history and may conduct a physical examination. Laboratory tests are commonly used to help establish the diagnosis and guide treatment.
Urine testing: A urine sample can be examined for signs of infection, including white blood cells and bacteria.
Urine culture: The sample may be sent to a laboratory to identify the bacteria responsible and determine which antibiotics are likely to be effective.
Blood tests: These may be needed to assess the severity of the infection or identify signs that it is affecting the body more widely.
Imaging tests: An ultrasound or other imaging examination may be considered when a doctor suspects a blockage, a structural problem or a complication, or when the patient is not responding as expected to treatment. Imaging is not necessary in every uncomplicated case.
How is a kidney infection treated?
Antibiotics are the main treatment for bacterial kidney infections. The medicine selected depends on the likely cause, laboratory results when available, local resistance patterns and the patient’s condition.
People who are well enough to take oral medicines may be treated with antibiotics by mouth. Those who are seriously ill, cannot keep medicines or fluids down, or have other complications may require hospital treatment and antibiotics administered through a vein.
Treatment commonly lasts seven to 14 days, although the appropriate duration depends on the antibiotic prescribed, the patient’s circumstances and the response to treatment. The course should follow the clinician’s instructions rather than a fixed duration applied to everyone.
Patients should take antibiotics as prescribed and seek reassessment if symptoms worsen or do not begin to improve within 48 hours of starting treatment. Persistent symptoms may indicate that the antibiotic is ineffective or that another problem needs investigation.
How does amoxicillin work?
Amoxicillin belongs to the penicillin group of antibiotics. It works by interfering with the formation of bacterial cell walls, which are necessary for bacteria to survive.
When the bacteria causing an infection are susceptible to amoxicillin, the medicine can help eliminate them. However, bacteria that are resistant to the antibiotic may continue to multiply, allowing the infection to persist.
This is why identifying the likely bacteria and choosing an effective antibiotic are important in treating kidney infections. Amoxicillin does not treat viral infections, and it is not effective against every type of bacteria.
What are the side effects of amoxicillin?
Amoxicillin can cause side effects, although not everyone experiences them. Common side effects include nausea, vomiting and diarrhoea.
Some people develop a skin rash or other allergic reactions. Severe allergic reactions can cause swelling of the face or throat, difficulty breathing or difficulty swallowing and require emergency medical treatment.
Anyone who develops severe or persistent side effects while taking amoxicillin should contact a healthcare professional. A history of allergy to penicillin should be disclosed before the medicine is prescribed.
When should you seek medical attention?
Suspected kidney infections require prompt medical assessment. Seek urgent medical care if you have fever or chills accompanied by pain in your back or side, particularly if you also experience painful urination, nausea or vomiting.
Seek emergency care for signs of a potentially serious infection, including confusion, difficulty breathing or severe deterioration in your condition. People who are pregnant, have weakened immune systems or have known urinary tract abnormalities may need additional assessment because their risk of complications can be higher.
Can amoxicillin cure a kidney infection?
Amoxicillin can treat a kidney infection in selected cases when the bacteria responsible are susceptible to the antibiotic. It should not, however, be regarded as a universally effective treatment.
The appropriate antibiotic and treatment duration should be determined by a healthcare professional, with urine culture results used to guide the choice when indicated. Prompt diagnosis and effective treatment help reduce the risk of complications.
