UTI vs Kidney Infection: How to
Tell the Difference and What to Do

Written by Kathleen Morrison
Medically Reviewed by Dr. Shannon Chatham, DO, a healthcare provider affiliated with Wisp

Key takeaways:

• A UTI typically stays in the lower urinary tract (bladder and urethra); a kidney infection means bacteria have traveled up to the kidneys.
• Burning, urgency, and cloudy urine usually signal a bladder infection; fever, chills, back pain, nausea, and vomiting are classic symptoms of a kidney infection.
• A UTI left untreated can spread to the kidneys, so acting early matters.
• Uncomplicated UTIs can often be assessed by our providers and may be treated with prescription antibiotics; kidney infections always require in-person care.
• Knowing the differences between the two helps you respond appropriately and fast.

Your body just sent you a "check engine" light, and now you're spiraling down a WebMD rabbit hole at 11 PM trying to figure out whether you have a run-of-the-mill UTI or something scarier. We've all been there.

The silver lining is that understanding the difference between a UTI and a kidney infection is actually pretty straightforward once you know what to look for.

A UTI is a bacterial infection confined to the lower urinary tract: your bladder and urethra. A kidney infection (pyelonephritis) occurs when the infection travels further up, reaching one or both kidneys.

For an uncomplicated UTI, you can often get prescription UTI antibiotics without setting foot in an in-person waiting room. For a kidney infection, you need in-person care, fast.

Here's how to tell them apart.

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What's actually going on in your urinary system?

Your urinary system includes your kidneys, ureters, bladder, and urethra—basically a whole plumbing network dedicated to filtering waste and getting it out of your body.

A urinary tract infection happens when bacteria (usually E. coli from your digestive tract) enter through the urethra and multiply in the bladder.

This is called cystitis, and it's incredibly common, especially in people with a shorter urethra, which gives bacteria a quicker path to the bladder.

A kidney infection, medically known as pyelonephritis, is a type of urinary tract infection that has traveled further up. Bacteria move from the bladder, through the ureters, and into one or both kidneys.

Once it's there, the infection may be more serious, harder to clear, and more likely to escalate quickly.

Symptoms of UTIs vs kidney infections

This is the part that matters most, and it often comes down to where you feel it and how bad you feel overall.

Symptoms of UTIs (bladder level)

Classic UTI symptoms tend to center around your bathroom habits:

• A strong, persistent urge to urinate, even when your bladder is basically empty
• Pain when urinating (that burning, stinging feeling)
• Urine that looks cloudy, smells stronger than usual, or has a pinkish tint
• Feeling like you can't fully empty your bladder
• Discomfort in abdomen
• Dull, aching in the lower back

You might feel pretty miserable, but you generally don't feel like you've been hit by a truck.

Symptoms of a kidney infection (upper urinary tract)

Symptoms of a kidney infection hit differently: harder, wider, and more body-wide. The infection has spread beyond your bladder, and your immune system knows it.

Watch for:

• Fever 100.4F or above, chills, or shaking
• Flank pain, which is a dull, persistent ache between your ribs and hips on one or both sides of your back (back pain that's distinctly different from a muscle ache)
• Nausea or vomiting
• Feeling generally flu-ish or exhausted in a way that a bladder infection just doesn't cause
• You may still have typical UTI symptoms alongside all of the above

The overlap between similar symptoms is what makes UTI vs kidney infection tricky to self-diagnose. But fever, chills, or back pain are big red flags that something has moved north of your bladder and is worth discussing with an in-person provider.

Causes and how each infection spreads

Both UTIs and kidney infections are typically caused by bacteria entering through the urethra. The key difference is how far the infection travels.

A UTI stays in the lower urinary tract: the urethra and bladder. A kidney infection typically starts the same way, but bacteria make the upward journey from the bladder, through the ureters, and into the kidneys.

This is why a UTI left untreated (or one that isn't fully cleared) is one of the most common routes to a kidney infection.

How a UTI can spread to the kidneys

Most kidney infections start as bladder infections that weren't treated in time. Bacteria sitting in the bladder can travel up through the ureters and settle into kidney tissue. And this upward migration can happen within days (sometimes within 24 hours in frail or vulnerable individuals) if a UTI is left untreated.

A few things may speed up the process:

• Certain medical conditions like diabetes
• Dehydration (less urine flow = less flushing)
• Not being able to fully empty your bladder
• A kidney stone blocking the ureter and trapping bacteria
• Vesicoureteral reflux, a condition where urine flows backward toward the kidneys
• A weakened immune system

Less commonly, bacteria can spread through the bloodstream from an infection elsewhere in the body, but the upward path from a bladder infection is by far one of the most common routes.

Diagnosing the two conditions

Because bladder UTIs and kidney infections affect the same urinary tract, testing can look similar in both cases.

A urine test may show signs of infection, but it can't tell you on its own whether that infection is in the bladder or has reached the kidneys.

That's where your symptoms and an in-person physical exam become especially important.

How an in-person provider diagnoses a kidney infection

At-home UTI test strips can screen for UTIs, but they can't assess kidney involvement.

If your symptoms suggest the infection may have spread to the kidneys, an in-person provider will typically:

• Review your symptoms and medical history
• Perform a physical exam, including checking your vital signs and assessing for costovertebral angle (CVA) tenderness
• Order a urinalysis and urine culture to identify bacteria and guide treatment
• Run blood tests to check whether the infection has entered the bloodstream
• Order imaging, like an ultrasound or CT scan, to look for kidney stones, abscesses, or structural issues in the urinary system

This level of evaluation is only possible in person, which is why kidney infection symptoms always warrant a visit to an in-person provider or emergency care.

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Treatment: UTI vs kidney infection

Although UTIs and kidney infections are part of the same spectrum of urinary tract conditions, their treatment approaches vary.

UTI treatment

Uncomplicated UTIs are typically addressed with a short course of prescription antibiotics.

Your provider will determine the most appropriate prescription antibiotic for you based on your symptoms, medical history, any known allergies, and local resistance patterns.

A few commonly prescribed options include:

Nitrofurantoin (Macrobid)

It's a commonly prescribed antibiotic for bladder infections, taken twice daily for 5 days.

Common side effects of Nitrofurantoin may include:

• Headache
• Mild diarrhea
• Dizziness
• Gas
• Upset stomach
• Vaginal itching or discharge

This is not a complete list of risks and side effects, and others may occur. If symptoms worsen or you notice signs of an allergic reaction, contact a provider right away.

Sulfamethoxazole/Trimethoprim (Bactrim)

It's a combination antibiotic typically prescribed as a 3-day course, taken twice daily.

Common side effects of Bactrim may include:

• Nausea
• Vomiting
• Loss of appetite
• Skin rash

This is not a complete list of risks and side effects, and others may occur. If symptoms worsen or you notice signs of an allergic reaction, contact a provider right away.

Fosfomycin (Monurol)

It's a single-dose option mixed with water and taken orally. One and done!

Common side effects of fosfomycin may include:

• Diarrhea
• Nausea
• Headache or dizziness
• Rash
• Weakness
• Back pain or menstrual pain

This is not a complete list of risks and side effects, and others may occur. If symptoms worsen or you notice signs of an allergic reaction, contact a provider right away.

Kidney infection treatment

Kidney infections require in-person evaluation and care.

A healthcare provider will typically diagnose a kidney infection based on your symptoms, a physical exam (including checking for tenderness over the kidneys), and urine and blood tests to look for signs of infection. Once diagnosed, treatment usually involves a longer course of antibiotics than is typically prescribed for a bladder infection.

If you're severely ill, pregnant, unable to keep fluids down, or have a weakened immune system, IV antibiotics and hospitalization may be necessary. This is not a situation to manage on your own or wait out.

When to seek medical care, and when to go to the ER

This part isn't meant to scare you; it's just important. Here's how to think about it:

For uncomplicated UTI symptoms, you can often get fast, discreet care without stepping into an in-person waiting room.

Online UTI consultations can connect you with a licensed provider who can assess your symptoms and, if medically appropriate, send a prescription to your local pharmacy the *same day.

*Most prescriptions are sent to your pharmacy within 3 hours of completing your medical intake form and phone call or video chat when necessary. Pending retail pharmacy hours.

Seek prompt medical attention, including urgent or emergency care, if you have:

• Fever 100.4°F or above, alongside urinary symptoms
• Chills or shaking
• Severe back pain or flank pain
• Nausea or vomiting
• Symptoms that are rapidly getting worse
• Blood in your urine paired with other warning signs

If you're pregnant, have kidney disease, have a history of kidney problems, or have a weakened immune system, don't wait.

Kidney infection can cause serious complications, including kidney damage and, in severe cases, bacteria entering the bloodstream (sepsis), which is a medical emergency.

Kick UTIs to the curb

Understanding the difference between a UTI and a kidney infection (and acting on it quickly) can genuinely help protect your health. A bladder infection caught early can be very manageable.

A kidney infection that gets to escalate? That's a different story.

Wisp offers same-day, judgment-free care from licensed providers who can assess whether you need UTI treatment and, if so, send a prescription to your local pharmacy*.

*Most prescriptions are sent to your pharmacy within 3 hours of completing your patient intake form and video or secure chat when necessary. Pending retail pharmacy hours.

This blog post is for informational and educational purposes only and should not be taken as professional advice. Always consult with a qualified professional before making any decisions based on the information provided here.