References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Mycoplasma genitalium (often shortened to M. genitalium or Mgen) is a sexually transmitted bacterial infection that can cause urethritis, pelvic inflammatory disease and other problems. Yes, it can be cured with antibiotics — but treatment is becoming more complex because the bacteria are developing resistance to commonly used drugs. Getting the right treatment requires proper testing.
Here’s what you need to know.
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What Is Mycoplasma Genitalium?
Mgen is a tiny bacterium that infects the genital and urinary tract. It was only identified in the 1980s and has since been recognised as a significant cause of:
- Non-gonococcal urethritis in men
- Cervicitis in women
- Pelvic inflammatory disease (PID)
- Some cases of infertility
- Possible link to preterm birth
Symptoms
| In Men | In Women |
|---|---|
| Discharge from the penis | Unusual vaginal discharge |
| Burning or pain during urination | Pain during sex |
| Pain in testicles | Bleeding between periods or after sex |
| Often no symptoms | Pelvic or lower abdominal pain |
Many people with Mgen have no symptoms.
Testing
Mgen is diagnosed using a nucleic acid amplification test (NAAT) on a urine sample or genital swab. Crucially, modern tests can also check for macrolide resistance mutations — this is important because it guides treatment choice.
Treatment
First-line treatment depends on whether macrolide resistance is present:
| Situation | Treatment |
|---|---|
| No macrolide resistance | Doxycycline 100mg twice daily for 7 days, then azithromycin 1g stat, then 500mg daily for 2 days |
| Macrolide resistance present | Doxycycline 7 days, then moxifloxacin 400mg daily for 10 days |
| Pregnancy | Specialist advice needed |
Single-dose azithromycin (the older treatment) is no longer recommended because it often fails and drives resistance.
Antibiotic Resistance
Mgen has developed rapid resistance to macrolides (azithromycin) globally. UK resistance rates are high and rising. This is why:
- Proper testing with resistance profiling is important
- Single-dose azithromycin is no longer recommended
- Treatment success should be confirmed with a test of cure
Test of Cure
Unlike many STIs, Mgen treatment is followed by a test of cure, usually 3-5 weeks after completing antibiotics. This confirms the infection has cleared. If it hasn’t, second-line treatment is used.
Partner Treatment
Current partners should be tested and treated to prevent reinfection. Clinic staff can help with partner notification.
Read more: What is chlamydia? | What is gonorrhoea? | LGV guide
Frequently Asked Questions
Is Mgen always curable?
Yes, but treatment is becoming more complex due to antibiotic resistance. Proper testing, targeted treatment and test of cure give the best chance of clearing the infection.
Do I need a test of cure?
Yes. UK guidelines recommend confirming cure with a follow-up test 3-5 weeks after finishing treatment.
Can Mgen cause infertility?
Untreated Mgen is a possible cause of pelvic inflammatory disease, which can lead to infertility. Prompt treatment reduces this risk.
Related reading
- Abnormal Genital Discharge and Chlamydia
- Can You Get Chlamydia From Kissing?
- Can You Have Chlamydia and Test Negative?
- Chlamydia and Gay Men: What to Know
- Can You Get Chlamydia From Oral Sex?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
