What is a urinary tract infection (UTI)?

A urinary tract infection (UTI) is an infection of the urinary system. This type of infection can involve your urethra (a condition called urethritis), kidneys (a condition called pyelonephritis) or bladder, (a condition called cystitis).

Your urine typically doesn’t contain bacteria (germs). Urine is a byproduct of our filtration system—the kidneys. When waste products and excess water is removed from your blood by the kidneys, urine is created. Normally, urine moves through your urinary system without any contamination. However, bacteria can get into the urinary system from outside of the body, causing problems like infection and inflammation. This is a urinary tract infection (UTI).

What is the urinary tract?

The urinary tract makes and stores urine, one of the body's liquid waste products. The urinary tract includes the following parts:

  • Kidneys: These small organs are located on back of your body, just above the hips. They are the filters of your body — removing waste and water from your blood. This waste becomes urine.
  • Ureters: The ureters are thin tubes that carry urine from the kidneys to your bladder.
  • Bladder: A sac-like container, the bladder stores your urine before it leaves the body.
  • Urethra: This tube carries the urine from your bladder to the outside of the body.

How common are urinary tract infections (UTIs)?

Urinary tract infections are very common, occurring in 1 out of 5 women sometime in their lifetime. Though UTIs are common in women, they can also happen to men, older adults and children. One to 2% of children develop urinary tract infections. Each year, 8 million to 10 million visits to doctors are for urinary tract infections.

Who gets urinary tract infections (UTIs)?

Anyone can get a urinary tract infection, but they are more common in women. This is because the urethra (tube the carries urine out of the body) in females is shorter and closer to the anus, where E. coli bacteria are common. Older adults also are at higher risk for developing cystitis. This increased risk may be due to incomplete emptying of the bladder. There are several medical conditions that can be related to this, including an enlarged prostate or a bladder prolapse (a condition where the bladder falls or slips out of its usual position).

If you get frequent urinary tract infections, your healthcare provider may do tests to check for other health problems — such as diabetes or an abnormal urinary system—that may be contributing to your infections. People with frequent UTIs are occasionally given low-dose antibiotics for a period of time to prevent the infection from coming back. This cautious approach to treating frequent UTIs is because your body can develop a resistance to the antibiotic and you can get other types of infections, such as C. diff colitis. This practice is used very infrequently.

What’s the difference between a urinary tract infection (UTI) and bladder infection (cystitis)?

A urinary tract infection is a more general type of infection. There are many parts of your urinary tract. A UTI is a term for an infection that takes place throughout the urinary tract. A bladder infection, also called cystitis, is a specific infection. In this infection, bacteria makes its way into the bladder and causes inflammation.

Not all urinary tract infections become bladder infections. Preventing the spread of the infection is one of the most important reasons to treat a UTI quickly when you have symptoms. The infection can spread not only to the bladder, but also into your kidneys, which is a more complicated type of infection than a UTI.

What causes a urinary tract infection (UTI)?

Urinary tract infections are caused by microorganisms — usually bacteria — that enter the urethra and bladder, causing inflammation and infection. Though a UTI most commonly happens in the urethra and bladder, bacteria can also travel up the ureters and infect your kidneys.

More than 90% of bladder infection (cystitis) cases are caused by E. coli, a bacterium normally found in the intestines.

What are the symptoms of a urinary tract infection (UTI)?

A urinary tract infection causes the lining of the urinary tract to become red and irritated (inflammation), which may produce some of the following symptoms:

Other symptoms that may be associated with a urinary tract infection include:

  • Pain during sex.
  • Penis pain.
  • Flank (side of the body) pain or lower back pain.
  • Fatigue.
  • Fever (temperature above 100 degrees Fahrenheit) and chills.
  • Vomiting.
  • Mental changes or confusion.

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