The essentials

"Mycoplasma" on a report can mean two unrelated infections. Mycoplasma pneumoniae infects the airways: a slowly worsening cough, sometimes "walking pneumonia", most often in children. Mycoplasma genitalium is a sexually transmitted infection, often without symptoms, that is becoming hard to treat. Each has its own tests (throat swab, blood antibodies, urine PCR) and its own antibiotics.

What is mycoplasma, at a glance?

  • What it is: very small bacteria without a cell wall. This is why penicillin-type antibiotics (beta-lactams) do not work on them[3].
  • Mycoplasma pneumoniae: spreads by coughing and sneezing; causes chest colds, sore throat and pneumonia[1]. In children it is the most common bacterial cause of pneumonia needing hospital care; in adults, the second most common[1].
  • Mycoplasma genitalium (Mgen): a sexually transmitted infection of the urethra, cervix or rectum, often silent[9].
  • Key tests: a PCR test (NAAT) on a throat and nose swab for the lung infection[2][4]; a PCR on urine or a genital swab, ideally with a resistance test, for M. genitalium[10][11].
  • Not the same as: chlamydia or gonorrhea, which are other bacteria with other tests.

What are the symptoms of Mycoplasma pneumoniae?

Symptoms appear 1 to 4 weeks after contact and can last several weeks; some people have none[1]. The long incubation explains why outbreaks spread slowly through schools and families[6].

  • Common A "chest cold": tiredness, fever, headache, sore throat and a cough that gets slowly worse[1]. The cough is usually dry[7].
  • Common In children under 5: runny or stuffy nose, sneezing, wheezing, watery eyes, vomiting or diarrhea, rather than a clear pneumonia[1].
  • Possible Pneumonia: cough, fever and chills, shortness of breath[1]. It is often mild enough that people keep going, hence the name "walking pneumonia"[1].
  • Rare Complications: asthma attacks, encephalitis, hemolytic anemia, kidney problems, severe pneumonia, or a blistering rash of the mouth and skin[1].

Without antibiotics, cough and weakness can last up to a month in adults[7].

What are the symptoms of Mycoplasma genitalium?

Many people have no symptoms, and they can still pass the infection on[9].

  • Common Men: discharge from the penis and burning when peeing (urethritis)[9]. M. genitalium causes about 15% to 20% of urethritis that is not gonorrhea, and about 40% of urethritis that keeps coming back[10].
  • Common Women: vaginal discharge and burning when peeing[9]; it is found in 10% to 30% of cases of cervicitis[10].
  • Possible Lower belly pain or pain during sex, signs of pelvic inflammatory disease (PID)[11].
  • Rare Long-term effects in women: scarring of the tubes, ectopic pregnancy, infertility, chronic pelvic pain; it may be linked to preterm birth[9].

When should I see a doctor for mycoplasma?

When to see a doctor

  • Emergency: call 911 for difficulty breathing, lips turning blue, confusion or a child who is very drowsy or breathing fast. Seek care right away for any trouble breathing[1].
  • Within 24 to 48 hours for a cough or wheezing that keeps getting worse, a fever that lasts, or a person with asthma or a weak immune system[1]; also for severe lower belly pain with fever after sex, which can be PID[10].
  • At your next appointment for burning when peeing or a discharge that came back after treatment for an STI, or if a partner has M. genitalium[9][10].

How do you catch mycoplasma, and who is at risk?

The two infections have nothing in common except the bacterial family. You cannot catch M. genitalium from a cough, nor M. pneumoniae from sex.

  • Common M. pneumoniae spreads through droplets from coughing and sneezing[1]. It is most common in school-age and younger children[2], and in crowded places such as schools and shelters[7].
  • Common Waves every few years: increases are thought to occur about every 4 years[2]. After COVID-19 restrictions ended, a worldwide wave started in late 2023, at the same time in many countries, with a further large increase in the United States in 2024, including young children[2][6]. Deaths stayed rare[6].
  • Possible M. genitalium passes through vaginal or anal sex, including from a partner without symptoms; whether oral sex spreads it is still being studied[9].
  • Rare Serious M. pneumoniae disease is uncommon[2]; it is more of a concern in older adults and people with a weak immune system[7].

Which tests diagnose mycoplasma, and how do I read the results?

The right test depends on which mycoplasma your doctor suspects. A "mycoplasma test" ordered without saying which one is a common source of confusion.

Mycoplasma tests and what each one tells you
TestSampleWhat a positive result meansMain limit
M. pneumoniae PCR (NAAT), often in a respiratory panelThroat and nose swabBacterial DNA found: the preferred test, fast enough to guide treatment[4]Can stay positive for months; also found in children without symptoms[5]
M. pneumoniae IgM and IgG antibodies (serology)BloodA recent or past infectionLacks specificity; a single IgM is unreliable, especially in adults; IgM can persist for a long time[4][5]
Cold agglutininsBloodAntibodies that clump red cells in the cold; normal titer 1:16 or less[8]Positive in only about half of more severe cases, and in other diseases too[5][8]
M. genitalium NAATUrine, or vaginal, cervical, urethral or penile swabAn active sexually transmitted infection[10]Not for screening people without symptoms[10]
Macrolide resistance testSame sample as the M. genitalium NAAT"Mutation detected": azithromycin will likely fail[10][11]Not offered by every laboratory[10]
Fictitious example of a lab report (United States format)
TestResultReference rangeFlag
Mycoplasma pneumoniae PCR (respiratory panel)DetectedNot detectedA
M. pneumoniae IgMPositiveNegativeA
M. pneumoniae IgGNegativeNegative
Cold agglutinin titer1:64≤1:16H
Mycoplasma genitalium NAAT, urineNot detectedNot detected
  1. PCR "Detected": in a child with a worsening cough, this supports M. pneumoniae. In a person without symptoms it can be leftover or carried bacteria[5].
  2. IgM positive, IgG negative: fits a recent infection, but one IgM alone is not proof. A second blood sample at least 2 weeks later, showing rising antibodies, is more reliable[5].
  3. Cold agglutinins 1:64 (H): above the usual limit of 1:16; it supports the picture but other conditions also raise it[8].
  4. M. genitalium not detected: a separate test for a separate infection. The two results do not influence each other.
  5. "A" or "H" means outside the reference; your laboratory's own reference range applies.

A mycoplasma result rarely comes alone: it sits next to a blood count, a CRP or a urine test. BloodSense reads your whole report line by line and explains, in plain words, what fits together and what to ask your doctor.

Have my report explained

Other tests help judge severity, not the cause: a complete blood count, a CRP blood test, sometimes a procalcitonin test, and a chest X-ray[7]. If hemolytic anemia is suspected, a Coombs test can be added. For genital symptoms, a doctor usually tests for chlamydia and gonorrhea at the same time: see which STI tests to get.

Does mycoplasma need follow-up tests?

  • M. pneumoniae: no repeat PCR is needed once you feel better, since bacteria can be detected for up to 4 months without illness[5]. A child who is not improving after a few days on treatment should be seen again[3].
  • M. genitalium: a test of cure is not routinely needed if you had no symptoms and took a recommended treatment[10]. Go back if symptoms last more than a few days after treatment, because resistant strains are increasing[9].
  • Partners: sex partners of a person with symptoms should be tested and treated if positive[10].

How is mycoplasma treated?

Mycoplasma pneumoniae. Most mild infections clear on their own[1]. Pneumonia is usually treated with antibiotics: macrolides (such as azithromycin) for children and adults, tetracyclines (such as doxycycline) for older children and adults, and fluoroquinolones for adults[3]. Resistance to macrolides stays under 10% in the United States[3]; in a worldwide study it was about 2% in Europe but 71% in Asia[6]. If a person does not improve on a macrolide, doctors consider another drug, such as doxycycline[3].

Mycoplasma genitalium. Macrolide resistance markers are found in 44% to 90% of infections in the United States, Canada, Western Europe and Australia[10]. That is why US guidelines use two steps: doxycycline first, then azithromycin if the strain is sensitive, or moxifloxacin if it is resistant or untested[10]. Azithromycin cures 85% to 95% of sensitive infections, while doxycycline alone cures only 30% to 40%[11]. A single dose of azithromycin is no longer advised[10]. Doses and duration are set by your prescriber.

How can I prevent mycoplasma?

  • Wash hands often and cover coughs and sneezes[1].
  • If you or your child has asthma, watch for flares during the infection, a known complication[1].
  • Use condoms correctly every time: this lowers the risk of M. genitalium[9].
  • Take all the prescribed medicine and make sure partners are tested and treated: you can be infected again after treatment[9].

Questions to ask your doctor

  1. Which mycoplasma was tested: pneumoniae, genitalium, or another one?
  2. Was the result from a PCR or from antibodies, and does it prove a current infection?
  3. Do I need an antibiotic, or will this clear on its own?
  4. Was a macrolide resistance test done, and which treatment does it point to?
  5. Should my partner or my family be tested?

Frequently asked questions

Is mycoplasma the same as walking pneumonia?

Not exactly. Walking pneumonia is a mild pneumonia that lets you stay on your feet. Mycoplasma pneumoniae is its most common cause, but other germs can cause it too. Read our guide to pneumonia for the other causes.

How long is Mycoplasma pneumoniae contagious?

The bacteria pass on through coughing for as long as you cough, and the 1 to 4 week incubation means contacts may fall ill weeks later[1]. Hand washing and covering coughs matter for the whole household.

Can mycoplasma go away on its own?

A mild M. pneumoniae infection often does[1]. For M. genitalium, a positive test in a person with symptoms is treated, because untreated infection can harm fertility in women[9].

Why did amoxicillin not work for my cough?

Mycoplasma has no cell wall, which is what penicillin-type antibiotics attack. If mycoplasma is the cause, doctors switch to another family, such as a macrolide or doxycycline[3].

What about Mycoplasma hominis or Ureaplasma on my result?

These are different bacteria that often live in the genital tract. The testing and treatment rules for M. genitalium do not simply apply to them: ask your doctor whether the finding matters for your symptoms.

References

  1. Centers for Disease Control and Prevention. About Mycoplasma pneumoniae infection. May 18, 2026. cdc.gov (accessed November 6, 2026)
  2. Centers for Disease Control and Prevention. Clinical overview of Mycoplasma pneumoniae infection. May 18, 2026. cdc.gov (accessed November 6, 2026)
  3. Centers for Disease Control and Prevention. Clinical care of Mycoplasma pneumoniae infection. May 18, 2026. cdc.gov (accessed November 6, 2026)
  4. Centers for Disease Control and Prevention. Laboratory testing for Mycoplasma pneumoniae. May 18, 2026. cdc.gov (accessed November 6, 2026)
  5. Waites KB, Xiao L, Liu Y, Balish MF, Atkinson TP. Mycoplasma pneumoniae from the respiratory tract and beyond. Clin Microbiol Rev. 2017;30(3):747-809. doi:10.1128/CMR.00114-16 (accessed November 6, 2026)
  6. Meyer Sauteur PM, Zhang XS, Emborg HD, Sidorov S, et al. Global spatiotemporal dynamics of Mycoplasma pneumoniae re-emergence after COVID-19 pandemic restrictions: an epidemiological and transmission modelling study. Lancet Microbe. 2025;6(4):101019. doi:10.1016/j.lanmic.2024.101019 (accessed November 6, 2026)
  7. MedlinePlus Medical Encyclopedia. Pneumonia - mycoplasma. Reviewed August 19, 2024. US National Library of Medicine. medlineplus.gov (accessed November 6, 2026)
  8. MedlinePlus Medical Encyclopedia. Febrile/cold agglutinins. Reviewed April 27, 2026. US National Library of Medicine. medlineplus.gov (accessed November 6, 2026)
  9. Centers for Disease Control and Prevention. About Mycoplasma genitalium. January 31, 2025. cdc.gov (accessed November 6, 2026)
  10. Centers for Disease Control and Prevention. Sexually Transmitted Infections Treatment Guidelines, 2021: Mycoplasma genitalium. cdc.gov (accessed November 6, 2026)
  11. Jensen JS, Cusini M, Gomberg M, Moi H, Wilson J, Unemo M. 2021 European guideline on the management of Mycoplasma genitalium infections. J Eur Acad Dermatol Venereol. 2022;36(5):641-650. doi:10.1111/jdv.17972 (accessed November 6, 2026)

This page is general information. It does not replace the advice of a doctor, who interprets your results with your symptoms, your history and an examination.