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Mycoplasma genitalium (MG)

Find out about the symptoms, causes and treatment of mycoplasma genitalium. 

Mycoplasma genitalium, also known as MG or Mgen is the smallest bacterial sexually transmitted infection (STI). Most people with the infection don’t experience symptoms and it is not routinely tested without symptoms.

Signs and symptoms of MG

There are often no signs or symptoms for MG. If you do have symptoms, they can often take a while to appear and you might notice:

Signs and symptoms in people with a vagina:

  • Pain when peeing
  • Bleeding after sex
  • Painful bleeding between your periods
  • Pelvic and lower abdominal pain
  • Vaginal discharge

Signs and symptoms in people with a penis:

  • Discharge from the penis
  • Pain when peeing
  • Redness and irritation of the penis
  • Urethritis

If left untreated MG may cause further complications such as pelvic inflammatory disease (PID), premature birth and swelling of the testicles.


MG is linked with infertility but there are no studies to verify this.

The causes and spread of MG

MG is found in the semen (sperm) and vaginal fluids of people who have the infection. It can passed from one person to another through:

  • Unprotected vaginal sex
  • Unprotected anal sex
  • Unprotected oral sex (no evidence so unlikely)
  • Your genitals coming into contact with your partners genitals (no data)
  • Sharing sex toys without washing them or covering them with a condom with each use (no data)

You don’t need to have had lots of partners and your partner doesn’t need to have experienced symptoms to pass it on to you.

You cannot get MG from kissing, hugging, sharing baths or towels, swimming pools, toilet seats or from sharing cups, plates or cutlery.

MG is often present at the same time as other infections such as chlamydia which can make it harder to diagnose.

Testing for MG

The nurse or doctor will not routinely test people without symptoms, even if they have another STI such as chlamydia or gonorrhoea. This is because over-testing could lead to unnecessary treatment, which could lead to antibiotic resistance.

Testing for MG is really simple and usually involves a simple urine test or genital swab. For people with a penis, a urine sample is collected when the bladder has not been emptied for some time, when it’s likely the urine is most concentrated with bacteria. For people with a vagina, a swab ist taken of the vagina and cervix.

Treatment of MG

If left untreated MG can develop a resistance to antibiotics and become difficult to treat.

MG is treated with the antibiotics. If diagnosed with MG you are advised to avoid sex until you and your partner have been treated. This is because you might pass the infection back to each other. Use condoms until you have a test 5 weeks after starting treatment to make sure you are clear of MG. This is because some antibiotics may not kill off the infection.

Tell the nurse or doctor if you are pregnant or think you may be, or if you are breastfeeding as you might need a different antibiotic to the routine ones used.


It is important that you tell your current and any recent sexual partners (last six months) that you are being treated for MG, so that they can access treatment too.

All clinics offer to contact your partners either using a digital service called SXT, or send messages to them anonymously, inviting them to get checked for STIs. This is called partner notification and it doesn’t mention your name or information about your care.

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