Mycoplasma genitalium (Mgen) testing

What is Mycoplasma genitalium (Mgen) testing?

Mycoplasma genitalium (often shortened to Mgen) is a sexually transmitted bacterium. It can cause inflammation of the urethra (the tube urine passes through) in men and women, and is linked to cervicitis and pelvic inflammatory disease in women. Many people who carry it have no symptoms at all.

Importantly, Mgen is not part of routine STI screening, and testing people with no symptoms is not recommended. This is because there is no evidence that treating symptom-free people helps, and because Mgen easily becomes resistant to antibiotics. Unnecessary testing leads to unnecessary antibiotics, which makes resistance worse — for you and for everyone. UK guidance recommends testing only when there is a clear reason.

Testing is usually a swab (often self-taken from the vagina) or a urine sample, looking for the bacterium's genetic material. If Mgen is found, the laboratory usually also checks whether it carries resistance to the main antibiotic (a macrolide such as azithromycin), because a high proportion of cases do. This resistance test helps the clinician choose treatment that is more likely to work and avoids wasting antibiotics.

Types, options & approaches

There may be different ways to do this. The right approach depends on the clinical question and your circumstances.

Options at a glance

These are the main approaches described in this guide. The right option depends on the diagnosis, your goals and what your clinician thinks is safe.

Preparing for your test

• Expect to be tested only if you have relevant symptoms or a clear clinical reason — ask why the test is being done.
• For a urine test, the clinic may ask you not to pass urine for an hour or so beforehand.
• Mention current symptoms, recent partners, and any recent antibiotics.
• Tell the clinician about any allergies and other medicines.
• Tell them if you are or might be pregnant, as this affects treatment if Mgen is found.
• Ask about a full sexual-health check, as other STIs can cause similar symptoms.
• Be ready to discuss telling partners if treatment is needed; the clinic can help confidentially.

What happens

At a sexual health clinic, a clinician will check that there is a clear reason to test for Mgen, rather than testing routinely. If there is, you provide a sample — usually a self-taken vaginal swab or a urine sample — which is sent to the laboratory to look for the bacterium's genetic material.

If Mgen is detected, the laboratory usually also tests for resistance to the main antibiotic. This takes a little longer but helps the clinician choose treatment that is more likely to work.

Because symptoms overlap with other infections, you will usually be tested for other STIs at the same time. If treatment is needed, you will be advised about the medicines, avoiding sex until treatment is complete, and arranging treatment for partners.

Is this test right for me?

A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.

Before you decide

Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.

The most important point is that this test should be used selectively. Testing without symptoms or a clear reason can find a bacterium that may not be causing harm, leading to unnecessary antibiotics and more resistance. If you do need testing, the resistance result matters, so treatment may be guided by it rather than started immediately.

Published figures to discuss

Mgen test accuracy is generally good with modern genetic tests, but a positive result does not always mean Mgen is the cause of symptoms, and resistance is common. Reported resistance rates to macrolide antibiotics vary by population and over time, and we avoid quoting a single figure here. The key, well-established points are that resistance is common enough that treatment should be guided by resistance testing, and that asymptomatic screening is not recommended.

These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.

What happens afterwards

There is no physical recovery from the test. Afterwards, the main thing is waiting for the result (including resistance testing if Mgen is found) and following the clinic's advice about treatment, sex and partners if treatment is needed.

• No physical change from the test itself
• A short wait for results, slightly longer if resistance testing is done
• Symptoms improving over the days after starting treatment, if treated
• Being asked back for a test-of-cure after treatment

Aftercare

• Wait for the result and follow the clinic's advice before assuming you do or do not need treatment.
• If treated, take the full antibiotic course exactly as prescribed.
• Avoid sex until you and your partner(s) have completed treatment.
• Make sure partners are assessed and treated if advised.
• Attend any recommended test-of-cure after treatment.
• Return if symptoms persist or come back after treatment.
• Consider testing for other STIs if not already done.

• A clear reason for the test that you understand
• Knowing when and how you will get the result
• If treated: the full course collected and a plan to finish it
• A plan to avoid sex until treatment is complete
• A test-of-cure appointment if recommended
• The clinic's contact details if symptoms persist

⚠ Get urgent help if…

• Lower tummy or pelvic pain, fever, or pain during sex (possible pelvic inflammatory disease) — seek prompt review
• Symptoms that do not improve, or come back, after treatment
• Pain or swelling in the testicles
• Abnormal vaginal bleeding, especially after sex
• Signs of an allergic reaction to any prescribed antibiotic
• Worsening pain or difficulty passing urine

Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.

General guidance — it doesn't replace the specific advice your specialist gives you.

Results & realistic expectations

A positive result means Mgen has been found; the resistance result then guides treatment. A negative result means Mgen was not detected, but if symptoms continue, another cause should be looked for, as no test is perfect.

Because Mgen can be present without causing harm, a positive result is interpreted alongside your symptoms. The clinic decides whether treatment is needed, rather than treating every positive automatically — this protects you from unnecessary antibiotics and helps limit resistance.

A test result reflects your situation at the time. Mgen can be caught again from a new or untreated partner, and there is no lasting immunity. Because resistance is common, a test-of-cure after treatment is often advised to confirm the infection has actually cleared.

Related tests, treatments or support

Mgen testing is usually combined with testing for other STIs (such as chlamydia and gonorrhoea), because the symptoms overlap and more than one infection can be present. If treatment is needed, partner testing and treatment are part of the process. Resistance testing is typically combined with the detection test when Mgen is found.

Follow-up & long-term care

If Mgen is found and treated, a test-of-cure some weeks later is often recommended because of resistance. The clinic will also follow up other STI results and advise on partner treatment. If the test is negative but symptoms continue, follow-up focuses on finding another cause.

Repeat, follow-on and what comes next

• Treatment may need to change depending on the resistance result.
• A test-of-cure after treatment is often recommended because resistance is common.
• Persistent or resistant infection may need specialist input and alternative antibiotics.
• A positive result is interpreted alongside symptoms rather than always treated automatically.

Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.

What good aftercare looks like

• A clear explanation of why the test was done and what the result means for you.
• Resistance-guided treatment if treatment is needed, with a named contact.
• A test-of-cure after treatment where recommended.
• Support to assess and treat partners confidentially.
• A clear route back to the clinic if symptoms persist or recur.

What affects the cost

Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:

• Whether the detection test alone, or also resistance testing, is performed.
• Whether it is part of a wider STI assessment or a single test, if done privately.
• The consultation fee, if using a private service.
• The cost of any treatment and follow-up testing.
• A test-of-cure after treatment if recommended.

• Confirmation of why the test is clinically indicated for you
• Whether resistance testing is included if Mgen is found
• How results are given and how long they take
• Whether treatment and a test-of-cure are included
• Whether testing for other STIs is included
• How partner notification and treatment are supported confidentially

On the NHS? Mgen testing is available on the NHS through sexual health clinics when there is a clear clinical reason; it is not offered as routine screening, and reputable services will not test people without symptoms.

You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.

Consent traps and marketing red flags

These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.

Choosing a specialist safely

• Check the specialist is on the GMC Specialist Register for this area.
• Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
• You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
• Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
• You're entitled to your total cost in writing — including any follow-up — before you decide.

How Vuemedics verifies every consultant →

Take this to your consultation. A good specialist will welcome every one of these.

• Why is Mgen testing being recommended for me specifically?
• If Mgen is found, will treatment be guided by the resistance result?
• What happens if the test is negative but my symptoms continue?
• Will I need a test-of-cure after treatment, and when?
• How will my partner(s) be assessed and treated?
• Should I be tested for other STIs at the same time?
• Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
• Will you be the specialist who carries out my test, and who looks after me afterwards?
• What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
• What does a realistic result look like — and what can this test not achieve?
• What are my options, including waiting, doing nothing for now, or choosing a different approach?
• Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
• What is the total cost in writing, including any follow-ups, and how much time do I have to decide?

Find a verified specialist for mycoplasma genitalium (mgen) testing

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How we made this page

Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →

Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.

Sources & standards: BASHH — UK guideline on Mycoplasma genitalium (2025) BASHH — Summary guidance on testing for STIs (2023) NHS Scotland Right Decisions — Mycoplasma genitalium Leeds Teaching Hospitals NHS Trust — Mycoplasma genitalium test

Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.

Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.