Causes of cystitis

Cystitis is usually caused by a bacterial infection, although it sometimes happens when the bladder is irritated or damaged for another reason.

Bacterial infections

Mostinfections are thought tooccur when bacteria that live harmlessly in the bowel or on the skin get into the bladder through the urethra (tube that carries urine out of your body) and start to multiply.

Cystitis is much more common in women than men, probably because the anus (back passage) is closer to the urethra in women and the urethra is much shorter.

It's not always obvious how the bacteria get into the bladder, but it can be caused by:

  • having sex
  • wiping your bottom aftergoing to the toilet particularly if you wipe from back to front
  • inserting a tampon or Urinary catheterisation (a thin tube inserted into the urethra to drain the bladder)
  • using a diaphragm for contraception

What can increase yourrisk?

There are a number of things that can increase your chances of developing an infection in your bladder. Some of these are outlined below.

Not being able to empty your bladder

If you're unable to empty your bladder fully, any bacteria that get inside may not be flushed out when yougo to the toiletand can multiply more easily.

You may not be able to empty your bladder fully if:

  • you have a blockage in your urinary system, such as a bladder stone
  • you're pregnant, as thebaby may be pressing on your bladder
  • (in men) you have an enlarged prostate gland that presses on the urethra


For women whohave been through the menopause , or are going through it, the lining of the urethra can shrink and become thinner because ofa lack of the hormone oestrogen.

The natural balance of bacteria in the vaginamay also change, which can allow potentially harmful bacteria to become more common.

Thiscan make the urethra more vulnerable to infection, which could spread into the bladder.


You're more likely to get cystitis if you have diabetes a condition where the level of sugar in your body becomes too high.

High levels of sugar in your urine can provide a good environment for bacteria to multiply, so any bacteria that get into the bladder are more likely to cause cystitis.

Other causes of cystitis

Cystitis can also be caused by damage or irritation to the urethra and bladder.

This can be the result of:

  • friction from sex
  • chemical irritants, such as those in perfumed soap or bubble bath
  • damage caused by acatheter or surgery on your bladder
  • radiotherapy to your pelvis or treatment with certain chemotherapy medicines
  • awoman's genitalshaving beendeliberately cut or changed for cultural, religious and social reasons (an illegal practice called female genital mutilation or FGM )

Cystitis has also been linked to recreational use of the drug ketamine.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 28 Nov 2016