Conditions guide

Urinary Tract Infection (UTI)

A urinary tract infection (UTI) is an infection in any part of the urinary system, most often the bladder. UTIs are very common and are usually caused by bacteria.

Last updated 3 sources

At a Glance

  • Most UTIs affect the lower urinary tract, meaning the bladder and urethra.
  • Bacteria from the bowel, especially E. coli, cause most UTIs.
  • Women get UTIs much more often than men, largely because the urethra is shorter.
  • Bacterial UTIs are commonly treated with antibiotics prescribed by a clinician.
  • An infection that spreads to the kidneys is more serious and needs prompt medical care.

What It Is

The urinary tract includes the kidneys, the ureters (tubes from the kidneys to the bladder), the bladder, and the urethra (the tube that carries urine out of the body). A UTI happens when germs, usually bacteria, enter the urinary tract and multiply.

An infection of the bladder is called cystitis, and an infection of the urethra is called urethritis. When an infection travels up to one or both kidneys, it is called pyelonephritis, or a kidney infection. Kidney infections tend to cause more severe illness and can lead to complications if not treated.

Some UTIs are described as uncomplicated, meaning they occur in otherwise healthy people with a normal urinary tract. Others are called complicated, such as those linked to pregnancy, urinary catheters, kidney stones, or other conditions that affect urine flow.

Common Terminology

Cystitis
Inflammation of the bladder, most often caused by a bacterial infection.
Pyelonephritis
An infection of the kidney, usually from bacteria that have traveled up from the bladder.
Urethritis
Inflammation of the urethra, which can be caused by bacteria, including some sexually transmitted infections.
Urinalysis
A test that checks a urine sample for signs of infection, such as white blood cells, nitrites, or blood.
Urine culture
A lab test that grows bacteria from a urine sample to identify the germ and which antibiotics are likely to work against it.
Recurrent UTI
Repeated urinary tract infections, often described as two or more in six months or three or more in a year.
Asymptomatic bacteriuria
Bacteria found in the urine without symptoms of infection; it often does not need treatment except in certain situations, such as pregnancy.

Common Causes and Associations

Most UTIs happen when bacteria from the skin or bowel enter the urethra and travel into the bladder. Several factors are associated with a higher chance of infection.

  • Female anatomy, since a shorter urethra makes it easier for bacteria to reach the bladder.
  • Sexual activity, which can move bacteria toward the urethra.
  • Certain types of birth control, such as diaphragms and spermicides.
  • Menopause, as lower estrogen levels change the tissues of the urinary tract.
  • Blockages or problems with urine flow, such as kidney stones or an enlarged prostate.
  • Use of a urinary catheter, especially for a long time.
  • Conditions that affect the immune system, such as diabetes.

Symptoms and Features

This is a general description of commonly reported symptoms, not a diagnostic checklist. Symptoms vary, and some people, especially older adults, may have few or unusual symptoms.

  • A burning feeling or pain during urination.
  • A frequent or urgent need to urinate, often passing only small amounts.
  • Cloudy, dark, or strong-smelling urine.
  • Blood in the urine, which may look pink, red, or brown.
  • Pressure or discomfort in the lower belly or pelvis.
  • Fever, chills, nausea, vomiting, or pain in the side or back, which are more often associated with a kidney infection.
  • New confusion or changes in behavior, which are sometimes the main sign of a UTI in older adults.

Tests and Evaluation

Clinicians usually combine a description of symptoms with simple urine tests. More testing may be used when infections are severe, recurrent, or complicated.

  • A urinalysis, often using a dipstick, to look for signs of infection.
  • A urine culture to identify the specific bacteria and guide antibiotic choice.
  • Blood tests in some cases, especially if a kidney infection is suspected.
  • Imaging such as ultrasound or CT scan in some people with recurrent or complicated infections, to look for blockages or structural problems.
  • Cystoscopy, a look inside the bladder with a thin camera, in selected cases of repeated infections.

Treatment Overview

Treatment depends on where the infection is, how severe it is, and individual health factors. Decisions about medicine are made with a healthcare professional.

  • Antibiotics are the main treatment for bacterial UTIs, and the specific drug and length of treatment are chosen by a clinician.
  • Completing the full course as prescribed is generally advised, even if symptoms improve early.
  • Kidney infections may require stronger treatment, and severe cases are sometimes treated in the hospital with intravenous (IV) antibiotics.
  • Pain relief for urinary discomfort may be discussed with a clinician or pharmacist.
  • For people with frequent infections, clinicians may discuss prevention strategies.
  • General habits often mentioned for prevention include drinking enough fluids, urinating after sex, and wiping from front to back.

When Professional Care May Be Discussed

UTI symptoms are a common reason people contact a healthcare professional. Some situations are generally considered more urgent.

  • Fever, chills, back or side pain, nausea, or vomiting along with urinary symptoms are often linked to kidney infection and are generally evaluated promptly.
  • Urinary symptoms during pregnancy are usually evaluated by a clinician because UTIs can affect pregnancy.
  • UTI symptoms in men, children, and older adults are typically evaluated by a healthcare professional.
  • Symptoms that do not improve after starting treatment, or that return soon after, are commonly discussed with a clinician.
  • Signs of severe illness, such as confusion, very low blood pressure, or difficulty staying awake, are generally treated as a medical emergency; in the US, people are advised to call 911.

Questions to Ask a Healthcare Professional

General questions people often find useful to bring to an appointment:

  • What part of the urinary tract is usually involved in a UTI?
  • What is the difference between a urinalysis and a urine culture?
  • Why is a urine culture sometimes needed before or after starting antibiotics?
  • What are the signs that an infection may have reached the kidneys?
  • What general steps are commonly recommended to help prevent UTIs?
  • When are repeated UTIs investigated with imaging or other tests?
  • How is antibiotic resistance relevant to UTI treatment?

Sources

This guide was written in plain language from the following authoritative references.

  1. Urinary Tract Infections — MedlinePlus (U.S. National Library of Medicine)
  2. Bladder Infection (Urinary Tract Infection—UTI) in Adults — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
  3. Urinary tract infections (UTIs) — NHS

Last updated October 8, 2026. FreeDoc guides are general educational information and are not a substitute for care from a qualified professional.