Overview of Nongonococcal Urethritis

Nongonococcal urethritis, or NGU, is defined as any form of urethritis not caused by gonorrhea. Approximately 15 to 40 percent of NGU cases are caused by chlamydia. Another 15 to 25 percent of cases are caused by mycoplasma. However, NGU can be caused by other sexually transmitted infections such as Trichomonas vaginalis. The herpes simplex virus can also cause NGU.

A male patient staring out of the window

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In most cases, if you are diagnosed with NGU, further testing will be performed to try and identify the cause of the infection. Often, bacteria can be identified through nucleic acid amplification test (NAAT) swab testing, which tests for viral or bacterial genetic material. This includes chlamydia, trichomonas, mycoplasma, and ureaplasma.

Mycoplasma, one of the most common causes of NGU, can be identified with a culture test, which is a test that involves waiting for the growth of the bacteria In a laboratory material. If you have mycoplasma or a high suspicion of mycoplasma, your provider will treat you with mycoplasma treatment guidelines.

It is possible that no pathologic species are identified on testing. In these cases, your healthcare provider may treat you with broad-spectrum antibiotics.

Who Gets NGU

NGU is more common In men due to the structure of the urethra, but it can affect women too.

Although people with vaginas can have infections of the urethra, those infections are not generally caused by STDs. Urethral infections (urethritis) are not the primary reason STDs in women are diagnosed. Instead, the equivalent diagnosis in women is likely to be cervicitis, which can involve infections with the same types of bacteria that are sometimes responsible for NGU.


Usually, the initial diagnosis of NGU is based on visible symptoms of urethritis. A definitive diagnosis may be based on urine tests or swabs.

If gonorrhea and chlamydia are ruled out, the cause of urethritis is often designated as NGU. Some healthcare providers will engage in further testing to attempt to identify the infectious pathogen. Further testing is often indicated if the initial course of treatment does not get rid of the NGU.

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  • Centers for Disease Control and Prevention. Sexually Transmitted Diseases Treatment Guidelines, 2010. MMWR 2010;59(No. RR-12).

  • Centers for Disease Control and Prevention. Sexually Transmitted Diseases Treatment Guidelines, 2015.

By Elizabeth Boskey, PhD
Elizabeth Boskey, PhD, MPH, CHES, is a social worker, adjunct lecturer, and expert writer in the field of sexually transmitted diseases.