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What Are the Best Antibiotics for a Kidney Infection?

By Meshell Powell
Updated Mar 03, 2024
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The kidneys are responsible for filtering waste materials from the body and forming urine. When bacteria enter the kidneys, usually through the tube known as the urethra that connects the bladder to the outside of the body, an infection may develop. Antibiotics are almost always used to treat these infections. Some available antibiotics for a kidney infection include fluoroquinolones, beta-lactam antibiotics, trimethoprim, and co-trimoxazole. Choosing the best antibiotics depends upon the severity and frequency of the infections as well as the overall health of the patient.

Fluoroquinolones are commonly used to treat a kidney infection. These medications are in a class known as broad-spectrum antibiotics. This means they may be used to treat a wide variety of infections, including kidney infections. This type of antibiotic is used primarily when there has been an ongoing history of kidney problems. A rash resembling measles may occur in some patients taking this type of antibiotic.

Beta-lactam antibiotics are among the most frequently used antibiotics for a kidney infection. This class includes penicillin and amoxicillin, among others. Potential side effects from this group of antibiotics include nausea, vomiting, or diarrhea. There have also been reports of severe allergic reactions when taking these antibiotics. Any facial swelling or difficulty breathing or swallowing should be considered medical emergencies.

Trimethoprim is another choice when considering treatments for a kidney infection. This type of antibiotic is used almost exclusively for the purpose of treating kidney infections. This antibiotic is not considered to be safe for women who are pregnant, especially during the first trimester. Other medical disorders, such as certain blood disorders, may prevent this type of antibiotic from being an appropriate choice. It is important for the patient to make sure the prescribing healthcare provider has a complete and accurate medical history before beginning treatment with this type of antibiotic.

Co-trimoxazole antibiotics are also among the more popular antibiotics for a kidney infection. This is actually a combination of two different medications, sulfamethoxazole and trimethoprim. Some patients have reported a variety of toxic effects when using this type of antibiotic. This has prompted several countries to ban the use of this type of medication. Medical professionals who prescribe co-trimoxazole antibiotics will typically monitor the patient closely during the course of treatment to ensure the health and safety of the patient.

Any medication has potential risks of negative side effects. For this reason, the patient should report any new symptoms to a medical professional right away. In many cases, the antibiotic can be changed to something that may work better for the individual patient.

How Long Does It Take For Antibiotics to Work on Kidney Infections?

Suffering from a kidney infection is one of the more unpleasant experiences a human being can have in this life. Fortunately, modern medicine has made treatment relatively easy. Even with something as painful as a kidney infection, a few rounds of antibiotics should clear it up. 

Most people suffering from a kidney infection should see their antibiotics kick in quickly. As long as treatment is received promptly, there’s no reason why it should take more than two weeks for the infection to heal completely. 

Patients will feel better within the first 24 hours of starting treatment. However, if patients do not see any improvements after the first day of antibiotics, they should consult with their physician. It’s uncommon for antibiotics to take longer than a day to start treating and easing symptoms. 

There are some exceptions to the two-week rule. Older adults may take longer to recover, even when antibiotics work on their infections. People who have underlying conditions may take longer to recover as well. 

Other Solutions When Antibiotics Don’t Work

If the antibiotics don’t work, patients with a kidney infection will likely need to stay at a hospital to receive more focused care and attention.

Doctors will often still prescribe antibiotics, as well as fluids. But, rather than the oral antibiotics taken at home, in-hospital antibiotics will most likely be delivered intravenously for more effective treatment. 

When patients have recurring issues, doctors may recommend seeing a kidney specialist or a urinary surgeon for a more precise evaluation. 

What Are the Warning Signs of a Kidney Infection?

Leaving a kidney infection untreated can lead to serious long-term health problems. Kidney infections could lead to kidney disease or failure, high blood pressure, or worse. If the infection spreads to the bloodstream, the patient could face a life-threatening condition called sepsis

Sepsis results from harmful microorganisms seeping into the blood and body tissue. These microorganisms could shut down vital organs or send a patient’s body into shock. It can also lead to death. 

Patients should pay careful attention to their body’s signals, especially if there is a possible kidney infection. In addition, patients should know what signs and symptoms to watch out for when it comes to kidney infections. 

The primary symptoms of a kidney infection are:

  • Fever
  • Chills
  • Back, flank, or groin pain
  • Abdominal pain
  • Frequent and painful urination
  • Burning sensation during urination
  • Nausea or vomiting

Other common symptoms include pus or blood showing in the urine or urine that is cloudy and smells. These are all signs that point toward a kidney infection. Again, the patient should seek medical attention immediately. 

Patients receiving treatment for a urinary tract infection but aren’t seeing improvements in their symptoms may have a kidney infection. It’s vital to make sure these patients consult a physician immediately if they’re concerned their UTI is not improving fast enough. 

Are Kidney Infections Serious?

Kidney infections are not always serious, but they can become serious if left untreated. When patients receive proper, prompt treatment, a kidney infection will rarely cause severe or irreversible harm. 

A kidney infection will generally cause patients to feel unpleasant or sick for a time. But, it usually won’t get any worse than that. Once patients begin antibiotic treatment, they should notice an improvement in their symptoms within a day. 

Untreated problems can turn serious quickly. For example, one sign that a kidney infection is more serious could be a treatment that doesn’t work as fast as expected. If this is the case, medical attention should be sought immediately. 

Are Kidney Infections Common?

Kidney infections make up a significant portion of the UTI hospital visits that occur in the United States every year. There are about 100,000 hospital visits for UTIs, many of which become kidney infections. 

While kidney infections are relatively common, certain people are more likely to experience them. For example, women are more likely to suffer from kidney infections than men. In addition, pregnant women are particularly susceptible to them. 

Other factors that could contribute to someone being prone to kidney infections include:

  • Having a UTI over the last 12 months
  • Experiencing any issues with blockage in the urinary tract
  • Being prone to kidney stones
  • Experiencing vesicoureteral reflux in one or both kidneys
  • Suffering from autoimmune diseases
  • Having diabetes
  • Spine injuries or nerve damage around the bladder
  • Suffering from urinary retention 

Things Patients With a Kidney Infection Should Avoid 

Patients with a kidney infection should actively avoid:

  • Soda
  • Canned food
  • Whole wheat bread
  • Bananas
  • Brown rice
  • Citrus, including orange juice
  • Dairy
  • Apricots
  • Pickles
  • Tomatoes
  • Prunes
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Discussion Comments
By anon284237 — On Aug 09, 2012

Don't take floroquinolone drugs! Look up "Quinolone Toxicity" and you'll find out why. It leaves "many" with horrific, permanent side-effects.

Penicillin would be a "much" safer choice. I personally avoid the doctor's visit and take oregano oil every two hours when I get a kidney infection -- knocks it out.

By Oceana — On Jun 04, 2012

@StarJo - I wish I could tolerate amoxicillin, but I am sensitive to it. It makes me so nauseous that I can’t function, and I really can’t stand to take it long enough for it to beat the infection.

When I got my first kidney infection, I didn’t feel sick from the amoxicillin right away. Instead, I got a strange bitter taste in my mouth.

This made everything I ate or drank taste bad. Even water had a horrible taste.

After a couple of days of this, I became nauseous. I felt as if I needed to vomit, but I couldn’t. I had to call my doctor and beg him for some other treatment.

By StarJo — On Jun 03, 2012

I have polycystic kidney disease, so I am prone to kidney infections. I have multiple cysts growing on each kidney, and they rupture from time to time, causing extreme pain.

The cysts can become infected, and the ensuing kidney infection causes soreness and difficulty getting comfortable in any position, sitting or standing. I have to take amoxicillin when I get an infection like this.

I’ve never had a kidney infection that amoxicillin couldn’t knock out. It’s good stuff, and it makes the soreness start to disappear in about a day.

By wavy58 — On Jun 03, 2012

@honeybees - I had a urinary tract infection turn into a kidney infection once. If I had gone to the doctor while it was still confined to my lower urinary tract, then I could have prevented this.

It started out with bladder cramps and super frequent urination. I thought it would go away on its own, so I waited over a week, and something worse happened.

I began to get a dull ache in my lower back, and one morning, I awoke and vomited just a few minutes after getting out of bed. I knew that I had to see my doctor then.

He gave me plain old penicillin. I was a little concerned, because nausea and vomiting were listed as possible side effects, and I already had these. However, instead of making them worse, the penicillin made me feel better.

By honeybees — On Jun 02, 2012

@Mykol - It is my understanding that a kidney infection is usually a complication of a typical urinary tract infection. A urinary tract infection affects the lower part of the bladder and when it progresses to the upper part, you have a kidney infection.

I think this is why they are often referred to as the same thing, and it makes sense why symptoms and treatment are often the same.

If either of these infections are not taken care of, they can lead to serious complications. My sister had such a severe urinary tract infection that she had to be hospitalized.

The technical term for a kidney infection is pyelonephritis. The only reason I know this is because I was having some problems with blood in my urine and had to go through all kinds of kidney testing. This went along with a UTI infection, but they needed to determine the cause.

By Mykol — On Jun 02, 2012

Is there a difference between urinary tract infection symptoms and kidney infection symptoms?

It seems like when talking about these infections they are often used interchangeably, and I wondered if they were the same thing?

I am very familiar with urinary tract infections as I have had many of them. It sounds like the symptoms and treatment are pretty much the same.

I have also read that women tend to get them more often than men because of the way our bodies are made. To my knowledge, my husband has never had a kidney or urinary tract infection.

There have been some years when I have one every few months. So far the same medication has always worked and cleared up the infection, but there have been times when my doctor is concerned I will build up a resistance to the antibiotic.

By SarahSon — On Jun 01, 2012

@andee - You are right about how uncomfortable a kidney infection can be. I have had this more than once and am getting pretty good at recognizing the symptoms of a kidney infection.

I always have the classic symptoms of back pain, a low grade fever and painful urination. This usually comes on suddenly and I know right away that I need some kind of antibiotic.

One thing I have noticed is that the antibiotic immediately helps me feel better. Usually I notice a difference in a few hours and that brings great relief.

Every time I have made an appointment with my doctor thinking I have a kidney infection, I have been right. I wish I could just call him up and he would prescribe a medication over the phone, but I always have to go in for an exam and give a urine sample.

By andee — On May 31, 2012

When I was a young girl, I remember having a kidney infection. I don't remember much about this other than it was painful and the kidney infection treatment was with antibiotics.

This was in the form of a liquid that needed to be refrigerated and taken a couple times a day. I also remember how bad this tasted and was glad when my infection was cleared up and I didn't have to take it any more.

I think they have made some significant changes in antibiotics since then. At that time, I was too young to swallow tablets or capsules, so the liquid was the best way to go. When I think about it, I have never known any kind of liquid medication to taste good!

The most important thing is that it takes care of the infection as this can be very painful and uncomfortable.

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