Notice: Users may be experiencing issues with displaying some pages on stanfordhealthcare.org. We are working closely with our technical teams to resolve the issue as quickly as possible. Thank you for your patience.
What causes a urinary tract infection (UTI) in teens and adults?
Bacteria that enter the urethra and travel up the urinary tract are the usual cause of UTIs.
Bacteria that normally live in the large intestine and are present in feces (stool) are the most common source of infection.
Sexual intercourse may move bacteria into the urinary tract. This happens most in women.
Catheters are a common source of infection in people who are in hospitals or who live in long-term care facilities. Catheters are small, flexible tubes inserted into the bladder to allow urine to drain.
Sometimes bacteria traveling through the blood or lymph system cause kidney or bladder infections.
Women tend to get more bladder infections than men. This is probably because women have shorter urethras. It's easier for the germs to move up to the bladder.
You may be more likely to get an infection if you have diabetes or you are pregnant. The chance that you will get a bladder infection is higher if you have any problem that blocks the flow of urine from your bladder. Examples include having kidney stones, an enlarged prostate gland, or a structural problem in the urinary tract.
Women who have repeated UTIs may have inherited genes that make them more likely to get these infections.