Mycoplasma genitalium (M. gen) facts

What is M. gen

Mycoplasma genitalium (M. gen) is a sexually transmitted infection that may be passed from one person to another during sex.

M. gen infects the urethra (in persons with a penis), the cervix (in persons with a vagina), and the rectum. M. gen infection in the throat appears to be rare.

How M. gen spreads

M. gen is spread during vaginal, anal, and very rarely, oral sex.

Symptoms of M. gen

People with a vagina:

• Vaginal discharge
• Unusual vaginal bleeding or bleeding after sex
• Burning or pain with urination
• Lower abdominal pain or pain during sex

People with a penis:

• Burning or pain inside the penis with urination
• Pain or itching in the head of the penis
• Discharge from the penis
• Pain, tenderness, or swelling of the testicle(s)

In the rectum:

• Often asymptomatic, but may cause rectal discharge, mucous, pain, or itching.
  
  

Although we know people without symptoms can carry M. gen, unlike gonorrhea or chlamydia there is no current evidence to recommend screening people without symptoms. Because of this, City Clinic only tests people with symptoms or partners of people who are diagnosed with M. gen.

How serious is M. gen

M. gen may cause a serious infection of the testicles (balls). In people with a vagina, M. gen could lead to a serious infection called pelvic inflammatory disease (PID). PID can damage the fallopian tubes and make a “tubal pregnancy” (outside the uterus) more likely, which can be fatal. PID can also lead to infertility—the inability to get pregnant.

How to treat M. gen

• M. gen is treated with antibiotics. The recommended treatment for M. gen is 7 days of doxycycline twice a day, followed immediately by 7 days of moxifloxacin once a day. It is important to take all of the pills you are given, even if you feel better before finishing them all.
• We do not provide partner packs for M. gen. Your sex partners should be tested for M. gen and treated if their test is positive. Otherwise, they can give the infection back to you or infect others.
• Don’t have sex until you complete the treatment and all symptoms have resolved.

How to avoid getting or spreading M. gen

• Condoms are effective in reducing the risk of infection.
• Do not have sex if you or a sexual partner has abnormal discharge, burning with urination, or any other symptom that could be due to an STI.

This information is provided by San Francisco City Clinic.

Visit our homepage at sf.gov/cityclinic.

Information last revised November 2025