Mycoplasma genitalium — often referred to as Mgen — is a sexually transmitted infection that has become increasingly difficult to identify and manage without the right diagnostic tools. Many people affected by Mgen experience no obvious symptoms, while others notice mild signs that can easily be attributed to other causes. Understanding why Mycoplasma genitalium testing matters, and why this infection presents such a growing challenge, may help inform decisions about sexual health.

Our clinic provides confidential STI testing services. We do not provide GP services or dermatology consultations, but we can advise on appropriate next steps if further medical care is needed.

What is Mycoplasma genitalium and why is it easy to miss?

Mycoplasma genitalium is a bacterial STI that can affect the urogenital tract in both men and women. It does not always produce clear or distinctive symptoms, which means it can go undetected for extended periods. Even when symptoms do appear, they can closely resemble those caused by other common infections such as chlamydia or non-specific urethritis.

Mgen may be associated with symptoms such as:

Unusual discharge from the penis or vagina
Burning or discomfort when urinating
Pelvic discomfort or pain in some cases
Bleeding between periods or after sex in some women
Mild urethral irritation in men

Symptoms such as these do not automatically indicate Mycoplasma genitalium or any STI. They may arise from irritation, hormonal changes, urinary tract conditions, or other infections. Because symptoms alone cannot confirm the cause, Mycoplasma genitalium testing may help provide clarity when there has been potential exposure or symptoms persist.

Possible causes of similar symptoms may include:

Urinary tract infections (UTIs)
Bacterial vaginosis
Thrush or candida overgrowth
Hormonal fluctuations
Irritation from products or friction
Other STIs such as chlamydia or gonorrhoea

Symptoms alone cannot confirm a Mycoplasma genitalium infection.

When could these symptoms be linked to Mgen?

If symptoms such as unusual discharge, pelvic discomfort, or urinary irritation persist beyond a short period — particularly following unprotected sex or a new sexual partner — Mycoplasma genitalium testing may be worth considering. In some cases, there are no symptoms at all, yet infection may still be present. Testing is the only reliable way to determine whether Mgen is involved.

Understanding Mycoplasma genitalium as an infection

Mgen is a small bacterium that attaches to cells in the urogenital tract. It was first identified in the 1980s but has only more recently been recognised as a significant cause of urethritis and cervicitis. It is estimated to affect a meaningful proportion of sexually active adults, though precise figures are difficult to establish given how frequently it goes undiagnosed. Standard STI screening panels do not always include Mgen, which contributes to its under-detection.

Common non-STI causes of similar symptoms

Many symptoms associated with Mgen can arise from entirely unrelated causes. Urethral irritation, for example, may result from soap products, lubricants, or synthetic fabrics. Discharge variations can be linked to hormonal shifts throughout the menstrual cycle. Pelvic discomfort may be associated with conditions such as endometriosis or ovarian changes. It is important not to assume that symptoms indicate an STI without appropriate testing.

Why antibiotic resistance is making Mgen harder to treat

One of the most significant challenges with Mycoplasma genitalium is its growing resistance to commonly used antibiotics. Azithromycin, which was previously a first-line treatment, is now ineffective in a substantial proportion of Mgen cases due to resistance mutations. This means that treatment without prior resistance testing can not only fail to clear the infection but may actively encourage further resistance.

Specialist testing for Mgen now often includes resistance-guided analysis, which helps clinicians select the most appropriate treatment pathway. A Macrolide Resistance Test for Mgen can identify whether a strain is likely to respond to standard antibiotic treatment. Without this level of diagnostic precision, treatment may be ineffective even when the infection has been identified.

How Mgen symptoms can overlap with other STIs

Mgen shares many symptoms with other STIs, particularly chlamydia and gonorrhoea. Urethral discharge, pelvic pain, and intermenstrual bleeding are all symptoms that can occur across several different infections. Because these conditions can appear similar, a full STI screen may be more informative than testing for a single infection. Relying on symptoms to distinguish between conditions is not clinically reliable.

When Mycoplasma genitalium testing may be sensible

Testing for Mgen may be appropriate in several circumstances, including:

Persistent or recurrent urinary symptoms without a clear explanation
Unusual discharge that has not resolved
Following unprotected sex with a new or casual partner
When a partner has been diagnosed with Mgen or an unexplained STI
Recurrent non-specific urethritis or cervicitis
As part of routine sexual health screening

A specific Mycoplasma genitalium PCR test is required to confirm Mgen, as it is not routinely included in standard STI panels. If a partner has also been diagnosed, read our guide on why your partner may need their own separate Mgen test.

How STI testing for Mgen works

Mycoplasma genitalium is detected using a nucleic acid amplification test (NAAT), which analyses a urine sample or swab for the presence of the bacterium's genetic material. This type of test is significantly more sensitive than older testing methods and can also identify resistance markers when required.

Depending on individual circumstances and symptoms, testing may involve:

Urine samples — commonly used for urethral infections
Vaginal or cervical swabs — used in women to assess the lower genital tract
Rectal or throat swabs — in cases where exposure may have occurred at other sites
Laboratory analysis — samples are processed in accredited laboratories with results typically available within a few days

Results are provided confidentially. If you are also concerned about other STIs, a chlamydia test or gonorrhoea test can often be arranged alongside Mgen testing.

When symptoms are less likely to be related to Mgen

Temporary irritation following sex, shaving, or the use of new personal care products is unlikely to indicate infection. Similarly, minor discharge variations during different phases of the menstrual cycle are common and generally not cause for concern. If symptoms resolve quickly without recurrence and there has been no recent potential exposure to an STI, the cause may well be non-infectious.

Frequently asked questions about Mycoplasma genitalium

Can Mgen be present without any symptoms?

Yes. Many people with Mycoplasma genitalium experience no symptoms at all. This is one of the reasons it can go undetected for long periods without specialist testing.

Does a burning sensation when urinating always mean an STI?

No. Urinary discomfort has several possible causes, including urinary tract infections, dehydration, or irritation from products. Symptoms alone cannot confirm the cause.

Should I test even if my symptoms have disappeared?

In some cases, symptoms may ease without the infection clearing. If there has been potential exposure to Mgen, testing may still be appropriate even when symptoms are no longer present.

How soon after exposure can Mgen be detected?

Current guidance generally suggests testing is most reliable from around two to three weeks after potential exposure, though individual circumstances may vary.

Is Mgen included in standard STI screening?

Not always. Mgen requires a specific test and is not routinely included in all standard STI panels. Requesting it directly or opting for a comprehensive screen is advisable if it is a concern. Individual tests may be added depending on your circumstances.

Can Mgen be treated successfully?

In many cases, yes — particularly when resistance testing is carried out before treatment begins. Without resistance-guided testing, there is a higher risk of treatment failure.

When to seek medical advice

Whilst many symptoms are temporary and non-infectious, some warrant further assessment. Consider consulting an appropriate healthcare service if you experience:

Severe pelvic or abdominal pain
Sores, ulcers, or unusual skin changes in the genital area
Fever alongside genital symptoms
Symptoms that persist or worsen over time
Significant bleeding outside of a normal menstrual period

If symptoms persist or worsen, consultation with an appropriate healthcare service may be advised.

Confidential STI Testing in the UK

If you are concerned about possible Mgen symptoms or recent exposure, confidential STI testing appointments are available at our UK clinic. Testing decisions depend on symptoms, exposure history, and individual risk factors. Our team can advise on which tests may be suitable for your circumstances and guide you on appropriate next steps if further medical care is required.

Book a confidential STI test at our UK clinic.

Disclaimer: This article is for general informational purposes only and does not constitute medical advice, diagnosis, or treatment. Sexual health concerns should always be assessed in the context of individual circumstances, and if you are experiencing symptoms that are persistent, severe, or worsening, we recommend consulting an appropriate healthcare service. Please note that our clinic provides private STI testing services only.

Why is Mgen becoming harder to detect and treat without specialised testing?