Complicated vs. Uncomplicated UTI: How to Tell the Difference

A urinary tract infection (UTI) is an infection you want to go away quickly. Often, the treatment for a UTI is straightforward, and it goes away with a simple course of antibiotics. But some UTIs are considered “complicated” and may require a different kind of treatment. So it helps to know if you have a complicated versus uncomplicated UTI — and what that means for getting the most effective treatment. 

What is the difference between a complicated and uncomplicated UTI?

Most UTIs are uncomplicated. But healthcare professionals will sometimes diagnose a UTI as “complicated.” This helps identify infections that may be harder to treat or that have a higher risk of a complication. A complicated UTI is diagnosed by factors related to the person, as well as features of the infection itself. 

These factors are presented in the table below.

Below, we go into more detail about the difference between uncomplicated and complicated UTIs.

Uncomplicated UTI

An uncomplicated UTI is sometimes called a simple UTI. For a UTI to be uncomplicated, it needs to occur in a female who does NOT have:

• A fever 

• An active pregnancy 

• A condition that weakens their immune system 

• A catheter in place 

But that’s not all. An uncomplicated UTI must also be limited to the lower part of the urinary tract. The urinary tract is divided into:

• The upper urinary tract: This includes the kidneys and the ureters — the tube that carries urine from the kidneys to the bladder.

• The lower urinary tract: This includes the bladder and the urethra — the tube that allows you to empty your bladder.

And, finally, an uncomplicated UTI is caused by a common bacteria that’s known to cause UTIs. Most commonly, these are bacteria that are naturally present in the digestive system and around the genital area. 

EXPERT PICKS: WHAT TO READ NEXT

• Preventing urinary tract infections (UTIs): We’ll break down the most common causes of UTIs and what you can do to prevent them in the future. 

• Natural remedies for UTI: Most UTIs need antibiotics to get better. But sometimes they can go away on their own. At-home treatments like D-mannose and ibuprofen can help. 

• Best antibiotics: The best antibiotic for your UTI will depend on your medical history, symptoms, and type of infection.

Complicated UTI

A UTI is complicated if it happens to someone who is:

• Male 

• Pregnant 

• Immunocompromised, or when the immune system’s function is reduced 

• Using an indwelling catheter, a tube inserted into the bladder to drain urine 

A UTI is also considered complicated when the infection:

• Causes a fever

• Involves the kidneys (also called pyelonephritis)

• Leads to sepsis, which means the infection is serious enough to cause a large immune response 

• Is caused by a kidney stone

• Is caused by an unusual bacteria

What bacteria causes complicated vs. uncomplicated UTIs?

The majority of UTIs — and uncomplicated UTIs — are caused by a common bacteria called E. coli. 

Examples of other bacteria that cause UTIs include:

• Staphylococcus saprophyticus 

• Klebsiella

• Proteus

• Enterococci 

These and a wide variety of other bacteria can cause complicated UTIs as well. But complicated UTIs are more likely to be caused by drug-resistant bacteria. Complicated UTIs may also be caused by less common organisms, like:

• Pseudomonas aeruginosa

• Candida (a type of yeast)

What is the difference in symptoms of a complicated vs. uncomplicated UTI?

Typical symptoms of an uncomplicated UTI include:

• Pain or burning when urinating

• Blood in the urine (also called hematuria)

• Cloudy or smelly urine

• Frequent and urgent need to urinate

• Pain in the pelvic area

A complicated UTI will often cause the above symptoms as well. But any of these additional symptoms could be a sign of a complicated UTI: 

• Pain in the lower back or side 

• Fever and/or chills

• Joint or muscle aches

• Nausea and vomiting

So, if you have any of these symptoms, it’s a good idea to contact your healthcare team to make sure you’re on the right treatment. 

What is the difference in treatment of a complicated UTI vs. uncomplicated UTI?

An uncomplicated UTI is usually treated with antibiotics to fight the bacterial infection. Common antibiotics include:

• Trimethoprim / sulfamethoxazole (Bactrim, Septra)

• Nitrofurantoin (Macrobid)

• Cephalosporins, such as cefdinir (Omnicef) or cephalexin (Keflex) 

• Amoxicillin / potassium clavulanate (Augmentin)

The best antibiotic for you depends on which bacteria are most common in your community, any medication allergies, and details from any prior UTIs. 

Antibiotics are the first-choice treatment for UTIs. Antibiotics tend to help resolve symptoms faster. And they lower the chances of developing a complicated UTI, like a kidney infection (pyelonephritis). 

But for some people, uncomplicated UTI symptoms can resolve without antibiotics. Some studies suggest that if you’re low-risk, it might be safe to wait a few days before starting antibiotics. That way, you can see if your immune system clears the infection on its own. But experts still don’t have clear guidelines to say when this would be recommended. 

A person with a complicated UTI, however, always needs to be treated with antibiotics. They often need stronger antibiotics as well. Examples include: 

• Ciprofloxacin (Cipro) or levofloxacin (Levaquin) 

• Trimethoprim / sulfamethoxazole (Bactrim)

• Fosfomycin (Monurol)

• Ceftriaxone (Rocephin), which can be given as an injection into the muscle

Can a complicated UTI be treated at home?

Sometimes, a complicated UTI can be treated with antibiotics that are taken by mouth, and you can be treated at home. Other times, treatment for a complicated UTI may need IV antibiotics. In this case, a person usually needs to be hospitalized for treatment and monitoring. There are many different types of antibiotics that can be used for severe infections in a hospital setting. 

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Written by:

Karen Hovav, MD, FAAP

Karen Hovav, MD, FAAP, has more than 15 years of experience as an attending pediatrician. She has worked in a large academic center in an urban city, a small community hospital, a private practice, and an urgent care clinic.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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