Complications of a UTI aren’t common, but can be serious. These complications usually only affect people who already have a health problem (a pre-existing condition) such as diabetes or a weakened immune system (the body’s natural defence against infection).

Complications of UTI include:

Kidney infection

Kidney infection, medically known as pyelonephritis, can happen when bacteria travel from the bladder to the kidneys. A kidney infection doesn't usually pose a serious threat to your health if treated promptly, but it can make you feel very unwell. And, if a kidney infection isn't treated, it can get worse and cause permanent kidney damage.

Often the symptoms come on quickly, within a few hours, and they can make you feel feverish, shivery, sick and with a pain in your back or side.

Find out more about symptoms of kidney infection and treatment for kidney infection.

Kidney failure

Kidney failure is when the kidneys stop working properly. If a person has kidney failure (also known as renal failure), they may need to have artificial kidney treatment, called dialysis.

Find out more about dialysis.

Blood poisoning

Blood poisoning (sepsis) is a rare, but potentially fatal, complication of kidney infection. It happens when bacteria spreads from the kidneys into the bloodstream. Once bacteria are in your blood, the infection can spread to any part of your body, including all of the major organs.

Blood poisoning is a medical emergency that usually requires admission to a hospital intensive care unit (ICU) while antibiotics are used to fight the infection.

Find out more about symptoms of blood poisoning and treatment for blood poisoning.

If you’re pregnant

You’re more likely to get complications from a UTI when you’re pregnant, so it’s important to tell a doctor if you have any symptoms. Find out more about:

• UTI symptoms
• UTI treatment