When a UTI May Be More Serious Than You Think

A UTI is considered complicated when there are signs that the infection has spread beyond the bladder, such as:

• Fever
• Chills or shaking
• Feeling very ill or having other signs of illness, such as low blood pressure
• Pain in your side or lower back, near your kidneys
• Pain when a clinician gently taps your lower back during an exam
• Pyelonephritis (a kidney infection)
• UTI symptoms in someone who has a urinary catheter

Complicated UTIs and simple UTIs are caused by the same thing — usually bacteria. What makes the infection complicated is that the infection has spread beyond the bladder.

Some health conditions and urinary tract problems can raise the risk of a serious UTI or make a UTI harder to treat. These include having:

• A weakened immune system
• Kidney stones
• A urinary obstruction
• A urinary catheter
• Diabetes
• Recurrent UTIs

Being pregnant can also increase the risk.

Symptoms of a cUTI usually start as typical simple UTI symptoms, but there will also be one or more of these:

• Fever
• Chills
• Nausea and/or vomiting
• Pain in your back, side or groin
• Signs of sepsis, which include rapid heart rate, confusion, low blood pressure

A quick urine test called a urinalysis can tell your clinician that you have a UTI, but if you have a cUTI, you may need a urine culture, which is a separate urine test. This looks for specific bacteria and identifies which antibiotics will be most likely to work. If you have fever, low blood pressure, confusion or suspected sepsis, you’ll likely also have a blood test called a blood culture. Like a urine culture, this test looks for bacteria.

You might also have an ultrasound or computed tomography scan (CT scan) to look for conditions like an abscess, urine retention (urine staying in your bladder) or a blockage.

It’s important to treat any UTI as quickly as possible but even more so if it’s a cUTI. Some issues can make a cUTI harder to treat, such as:

• Having a blockage in your urinary tract
• Urinary retention
• Kidney stones
• Having a urinary catheter
• Having a weakened immune system
• Antibiotic-resistant bacteria

The first step in treatment is often a broad-spectrum antibiotic even before your test results come back. These antibiotics treat several types of bacteria at once. When your results come back with the type of bacteria that’s present, you might stay on that original antibiotic, or it may be changed to a more targeted one. Research is ongoing to find better treatments for cUTIs, and in June 2026, the FDA approved a new oral antibiotic for certain adults who have cUTIs including kidney infections, who have limited or no other treatment options.

Many people start feeling better within a few days of starting their antibiotic. If you don’t feel better or your symptoms are worsening, contact your clinician as soon as possible. Your treatment might be changed to a different one or you might need IV antibiotics. Then once the IV antibiotics start working, usually you’d be switched back to pills.

A primary care clinician, internist or hospitalist might treat your cUTI, but you could be referred to a urologist or an infectious disease (ID) specialist. A urologist specializes in treating conditions that affect the urinary tract, while an ID specialist can help choose the best antibiotics to treat the infection.

Aside from treating the infection, you may need pain relief medications if your pain is severe.

Unfortunately, we can’t prevent all UTIs. You can lower the risk of a simple UTI becoming complicated by seeking medical care as soon as you notice any UTI symptoms. Prompt treatment can help prevent the infection from spreading. Other things you can do include:

• Avoid urinary catheterizations when possible. This means if you have a catheter, check regularly about when you can have it removed.
• If you live with an indwelling urinary catheter:
  • Follow care instructions closely
  • Make sure urine is always flowing and the tube isn’t kinked or blocked
  • Always keep the collection bag lower than your waist
  • Stay hydrated

A urinary tract infection should always be taken seriously. Don’t ignore UTI symptoms. Seek urgent medical care if you have any symptoms of a cUTI, have a urinary catheter, feel very weak, are having trouble urinating or are pregnant. Call 911 or seek emergency care if you’re confused, fainting, having trouble breathing or feeling severely ill. Most UTIs, whether they’re simple or complicated, can be treated successfully, but the key is taking care of it quickly.