Mycoplasma Genitalium vs. Chlamydia: Key Differences

Quick answer: Mycoplasma genitalium and chlamydia are both bacterial STIs that cause similar symptoms — or none at all — but they differ in key ways: chlamydia is far more common and easy to cure, while Mgen is harder to treat because of antibiotic resistance. Both are diagnosed with a urine or swab NAAT.

Mycoplasma Genitalium vs. Chlamydia: What's the Difference?

Patients often come to me convinced these are the same thing, and I understand why — they behave alike day to day. Both are bacterial, both spread through sexual contact, both are frequently silent, and both can cause pelvic inflammatory disease if ignored. Where they part ways is how common they are, how they're treated, and how stubborn they can be.

Can You Tell Them Apart by Symptoms?

Honestly, no — and that's the point I make to patients. Both are silent much of the time, and when symptoms do show up they overlap heavily: discharge, burning with urination, pelvic discomfort. You can't tell which one you have by how you feel; only a test can. Our chlamydia guide covers its specific signs.

Testing

The good news is that the same technology finds both — a NAAT on urine or a swab. The catch is that Mgen isn't in every standard panel. So the scenario I see often: someone treated for chlamydia whose symptoms don't clear actually has Mgen that was never checked for. If that's you, ask specifically about Mgen testing.

Treatment: Where They Really Differ

This is the practical divide:

• Chlamydia is reliably cured with a single antibiotic — doxycycline for 7 days.

• Mgen needs a two-step, resistance-guided course because it's frequently resistant to the macrolides that used to work. See our mycoplasma genitalium treatment guide.

That difference is exactly why a chlamydia course sometimes leaves Mgen behind.

Can You Have Both?

Yes — co-infection happens, and because they share symptoms and testing, I'll sometimes check for both when symptoms persist. Mgen also overlaps with ureaplasma, another organism in the same family, which is worth keeping in mind if you're comparing them.

When to Seek Care

• Pelvic pain with fever.

• Symptoms that persist after chlamydia treatment — ask about Mgen.

• Symptoms during pregnancy.

Frequently Asked Questions

Is mycoplasma genitalium worse than chlamydia?
Not worse, but harder to cure because of resistance. Both can cause similar complications if left untreated.

Can chlamydia treatment cure mycoplasma genitalium?
Not reliably. Doxycycline lowers Mgen but usually needs a second antibiotic to clear it.

Can you have chlamydia and mycoplasma at the same time?
Yes. Co-infection happens, and testing for both may be done when symptoms persist.

The Bottom Line

Chlamydia and Mgen look alike but treat very differently — one is a simple cure, the other's resistance makes it trickier. If symptoms linger after chlamydia treatment, Mgen is worth checking. You can get tested to know which one you're dealing with.

Last reviewed: September 2026

Medical review: This article is for informational purposes only and does not constitute medical advice. Consult a provider about testing and treatment. Guidance is based on the CDC 2021 STI Treatment Guidelines and CDC STI information.