NSU

Non-specific urethritis (NSU) is one of the most common sexually transmitted infections (STIs) in men. If left untreated it can cause arthritis. 

It’s also known as non-gonococcal urethritis (NGU) when not caused by gonorrhoea.

Urethritis means inflammation of the urethra, which is the tube inside the penis that urine comes down.

Non-specific means the exact cause of the inflammation isn’t known, but it's caused by bacteria (often chlamydia) picked up from a partner’s mouth, vagina, rectum or penis during sex.

Women can also get NSU but it can be harder to diagnose as it does not cause many symptoms. However, it can lead to pelvic inflammatory disease (PID) if it's caused by chlamydia and left untreated. PID can be associated with an increased risk of infertility.

This page only covers NSU in men.

There may be no symptoms, but up to three weeks after becoming infected you might notice:

• a whitish discharge from your penis 
• peeing frequently 
• pain or burning when peeing
• irritation and soreness at the tip of your penis.

NSU is usually caused by bacteria.

They live inside a partner’s mouth, vagina, penis or rectum and get into your penis when you have unprotected oral, vaginal or anal sex.

You might also carry the bacteria on your fingers to your penis after touching an infected part of your own or someone else’s body.

Using condoms cuts the risk of NSU, which can also be caused by unprotected oral sex.

Sometimes NSU is inflammation caused by friction from masturbation and sex, or even a reaction to things like soap.

NSU can also be caused by the sexually-transmitted bacterium Mycoplasma genitalium (also known as MG or Mgen). It’s passed on through unprotected anal sex. Mgen has developed some antibiotic-resistant strains.

If you have HIV, having untreated NSU could make it more likely you will pass on HIV during unprotected sex. But if HIV drugs have made your viral load undetectable then NSU and other infections don’t appear to make you more likely to pass on HIV.

There’s a urine test for NSU, or a sample can be taken from the opening of the penis using a swab (a small cotton bud). This might be uncomfortable for a second or two.

A course of antibiotics will cure NSU. Sex should be avoided until the treatment is finished to avoid passing it on. Sexual partners also need to be checked and treated – a clinic can contact them anonymously.

Untreated NSU sometimes causes serious problems such as arthritis.

Most people get tested and treated for infections like NSU at sexual health (GUM) clinics. It's free and confidential and no-one else, including your GP, will be told about your visit. Some GP surgeries also test for and treat these infections.

The more people you have sex with (especially unprotected sex), the more chance you have of getting infections like NSU. You can have them without knowing, so regular check-ups are a good idea, especially if you're starting a new relationship and/or you want to stop using condoms with your partner.