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Non-gonococcal urethritis (NGU) can have a number of possible causes, such as an infection, irritation or damage to the urethra.

There are also many cases where no cause is found – this is sometimes known as non-specific urethritis (NSU).

If urethritis is caused by gonorrhoea, it is known as gonococcal urethritis.

NGU can also be caused by other sexually transmitted infections (STIs), such as chlamydia. Chlamydia is spread during unprotected sex (sex without a condom), including anal and oral sex.

Urethritis is more common among people who are at risk of STIs. This includes people who:

  • are sexually active
  • have had unprotected sex
  • have recently had a new sexual partner

A number of other infections can cause NGU. These are caused by other bacteria that usually live harmlessly in the throat, mouth or rectum.

These bacteria can cause NGU if they get into the urethra, which is the tube that carries pee from the bladder to the outside of the body. This can occur during oral or anal sex.

Infections that can cause NGU include:

  • Trichomonas vaginalis – an STI caused by a tiny parasite
  • Mycoplasma genitalium – tests for this condition have only recently been developed and are not available in all clinics yet; if you can't be tested, you will be treated as though you might have it
  • urinary tract infection
  • the herpes simplex virus – this can also cause cold sores and genital herpes
  • an adenovirus – usually causes a sore throat or an eye infection

It's possible for NGU to have a non-infectious cause. This is when something else leads to the urethra becoming inflamed. 

Non-infectious causes of NGU include:

  • irritation from a product used in the genital area – such as soap, deodorant or spermicide
  • damage to the urethra caused by vigorous sex or masturbation, or by frequently squeezing the urethra – some men may do this if they're worried they have an infection
  • damage to the urethra caused by inserting an object into it, such as a catheter – this can be done during an operation in hospital