Definition & Facts of Bladder Infection in Adults

In this section:

What is a bladder infection?

A bladder infection is an illness caused by bacteria. Bladder infections are the most common type of urinary tract infection (UTI).1 A UTI can develop in any part of your urinary tract, including your urethra, bladder, ureters, or kidneys.

Your body has ways to defend against infection in the urinary tract. For example, urine normally flows from your kidneys, through the ureters to your bladder. Bacteria that enter your urinary tract are flushed out when you urinate. This one-way flow of urine helps to keep bacteria from infecting your urinary tract. Learn more about your urinary tract and how it works.

Sometimes your body’s defenses fail and the bacteria may cause a bladder infection. If you have bladder infection symptoms, see a health care professional.

Most of the time, getting treatment right away for an infection in your urethra or bladder can prevent a kidney infection. A kidney infection can develop from a UTI that moves upstream to one or both of your kidneys. Kidney infections are often very painful and can cause serious health problems, so it’s best to get early treatment for a UTI.

When a bladder infection or other UTI is diagnosed and treated properly, most people won't have complications.

The urinary tract, showing the kidneys, ureters, bladder, and urethra.Most UTIs occur in the bladder. In a few cases, an infection can spread to one or both kidneys.

Is there another name for a bladder infection?

Bladder infections are also called cystitis. Sometimes people use the more general term, urinary tract infection (UTI), to mean a bladder infection, although UTIs can occur in other parts of the urinary system. UTIs that occur in the urethra only are called urethritis. A kidney infection is called pyelonephritis.

How common are bladder infections?

Bladder infections are common, especially among women. Research suggests that at least 40 to 60 percent of women develop a UTI during their lifetime, and most of these infections are bladder infections. One in 4 women is likely to have a repeat infection.1

Who is more likely to develop a bladder infection?

People of any age or sex can develop bladder infections, but women are at higher risk than men. Some people are more prone to getting these infections than others, especially those who have certain medical conditions or lifestyle factors.

You are more likely to develop a bladder infection if you

  • are sexually active
  • are a woman who has gone through menopause
  • are a woman who uses certain types of birth control, such as diaphragms or spermicide
  • have trouble emptying your bladder completely, like people with a spinal cord injury or nerve damage around the bladder
  • have a problem in your urinary tract that blocks, or obstructs, the normal flow of urine, such as a kidney stone or enlarged prostate
  • have an abnormality of the urinary tract, such as vesicoureteral reflux (VUR)
  • have diabetes or problems with your body’s immune, or natural defense, system
  • recently used a urinary catheter
  • had a UTI in the past

Women are more likely to develop a bladder infection than men, mainly due to differences in anatomy:

  • Women have a shorter urethra than men, which means bacteria have a shorter distance to travel to reach and infect a woman’s bladder.
  • In women, the opening to the urethra is closer to the rectum, where the bacteria that cause bladder infections live.
A young woman talks with a health care professional who is wearing a stethoscope.
People of any age or sex can develop a bladder infection. However, women are much more likely to develop this type of infection than men.

What are the complications of bladder infections?

If infections in the lower urinary tract, such as bladder infections, are not treated, they can lead to kidney infections. If you have a kidney infection, a health care professional will provide treatment to relieve your symptoms and help prevent complications.

Health care professionals routinely test pregnant women for bacteria in the urine because a bladder infection during pregnancy is more likely to become a kidney infection.

Complications from bladder infections are rare when you work with your health care provider to find the best treatment and complete it. If your infection is treated with antibiotics, it’s important to follow directions carefully and finish all the medicine, even after you start to feel better. If you stop taking antibiotics too soon, you may get another infection that is harder to treat.


Last Reviewed March 2017
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.

The NIDDK would like to thank:
Ann E. Stapleton, MD, FIDSA, FACP, University of Washington School of Medicine