What Is Mgen? The STI You Probably Haven’t Heard Of

Many of us haven’t heard of Mgen. If you're on TikTok, you may have seen a few videos about the bacterial illness circulating recently but even so, Mgen is something we need greater awareness of. It is estimated that two in every 100 sexually active adults between 16 and 44 years old in the UK have Mgen but it’s hard to know how accurate that figure is when it’s so rarely spoken about.

Mgen is worth adding to your arsenal of sexual health knowledge — you never know when it might be handy. 

Mgen, full name Mycoplasma genitalium, is a sexually transmitted infection (STI). It’s caused by a bacterium that infects the urinary and genital tracts of men and women. It can be spread by vaginal and anal sex, although transmission can occur even without penetration — in that respect, it’s been compared to chlamydia (which, in case you didn’t know, can also spread without penetration).

Don’t feel bad for not knowing about it, though. “Mgen was only discovered in 1981 and reliable testing only became available in 2017, so it is still considered a ‘new STI’,” explains Dr Neel Patel from LloydsPharmacy Online Doctor. 

Like chlamydia, Mgen is often symptomless. It’s thought that 80% of men and 50 to 70% of women who have Mgen don’t show any symptoms. If you do get any, Dr Patel says they usually appear one to three weeks after infection, and can be different for men and women.

Vaginal symptoms of Mgen include unusual discharge, pain during sex, bleeding after sex, painful bleeding between periods, and burning or itching in the genital area. Urinary symptoms of Mgen include pain when urinating, in the stomach or pelvis, and itchiness. Penile symptoms can appear as white discharge from the penis, burning or itching from the urethra and pain in the testicles. 

“One concern with Mgen is that it causes similar symptoms to chlamydia, despite being caused by a different bacteria,” Dr Patel says. “The danger here is that many doctors in the past have tried treating Mgen believing it to be chlamydia; as chlamydia treatment isn’t 100% effective against Mgen, it has led to a rise in antibiotic resistance.” 

It can be passed on through having unprotected vaginal or anal sex with someone who is infected with Mgen, explains pharmacist Abbas Kanani from Chemist Click. “You can also get it if you touch your genitals with infected fingers or by sharing sex toys which are not cleaned or covered with a condom.” A condom will reduce the risk of transmission but won’t completely eliminate it. 

Testing for Mgen isn’t routine at sexual health clinics so it tends to be done only if you present symptoms or if you’ve raised it as a concern. Dr Patel says you can request a test if you’re worried. “A test can be taken by a swab or urine sample. If your results come back positive then you should let your current sexual partners know as they should get tested too,” he says.

Research shows the number of gonorrhoea and syphilis diagnoses are at record-breaking highs, increasing by 8% and 9% respectively since 2022. According to official government statistics, diagnoses of chlamydia remained relatively stable in 2023. Mgen aside, Dr Patel recommends getting a routine STI test every three to six months if you have multiple sexual partners. 

It’s hard to say, as there isn’t as much data on Mgen compared to other STIs. Dr Patel says Mgen is relatively common despite being widely unheard of. Research from 2018 estimated that 2.3% of women and 1.1% of men between 21 and 23 years old had Mgen. The numbers are smaller across older age groups. These stats show it is much less common than, say, chlamydia, which affects 4% of women worldwide aged 15 to 49. What makes this STI so prevalent is its ability to go undetected. In the US, one study says 1 to 4% of the population has Mgen.

Mgen can clear on its own so please don’t panic. However, sometimes it doesn’t. Think of it like HPV — some people clear it and never know they had it; other people have intervention to check the HPV doesn’t turn into cervical cancer. Mgen sometimes needs treatment, and other times it doesn’t (though it isn’t linked to cancer in the way HPV is).

When treatment is required, it’s with a course of antibiotics, says Kanani. 

If left untreated, Mgen can lead to serious health conditions, warns Dr Patel: “It has been associated with pelvic inflammatory disease (PID), which has been linked to preterm births and miscarriages.” Kanani adds that men can experience inflammation of the testicles and the tubes carrying sperm, which has the potential to cause infertility. Mgen isn’t something to fear or worry about. But if things aren’t right down there — especially if a standard STI test has come back clear — it may be worth mentioning Mgen to your nurse or doctor for further testing.