Nongonococcal urethritis (NGU) is urethral inflammation that isn't caused by gonorrhea. The most common identified cause is Chlamydia trachomatis, followed by Mycoplasma genitalium, and sometimes Trichomonas vaginalis, herpes (HSV), or adenovirus. About half of cases have no organism found at all. Some are sexually transmitted; others trace to irritation or non-sexual factors.
with the right treatment
testing, not symptoms, decides
| Item | Value |
|---|---|
| Curable? | yes — with the right treatment |
| Tested by | NAAT / lab |
| Often | no symptoms |
| If you may have it | get tested — testing, not symptoms, decides |
What NGU actually is
NGU isn't a single germ — it's a syndrome, a pattern of inflamed urethra defined by what it isn't. When a clinician confirms urethritis but rules out gonorrhea, the label is "nongonococcal." That distinction matters because the causes, the right antibiotics, and the follow-up differ. The urethra is the tube that carries urine (and, in men, semen) out of the body, and when its lining gets inflamed you feel it as burning, itching, or discharge.
The leading culprits split into two groups. The clearly sexually transmitted ones are Chlamydia trachomatis, Mycoplasma genitalium, and Trichomonas vaginalis. Then there are non-sexual or less-classifiable triggers — HSV and adenovirus (often after orogenital contact), and sometimes plain mechanical irritation from a catheter, vigorous activity, or chemical exposure. And in roughly half of cases, even good testing turns up no organism, which is normal and doesn't mean the inflammation isn't real CDC, 2021.
Chlamydia
Chlamydia is the single most common identifiable cause of NGU and is firmly sexually transmitted. It often produces little or no discharge, which is exactly why it spreads so quietly — many people carry and pass it without ever feeling sick.
Mycoplasma genitalium
Mycoplasma genitalium is a sexually transmitted bacterium that's a major cause of NGU that persists or comes back after first-line treatment. It's harder to grow and was historically missed, so it tends to surface in the workup of persistent cases rather than at the first visit. It can also be carried without symptoms.
Trichomonas
Trichomonas vaginalis is a sexually transmitted parasite that sometimes causes NGU in men, often with mild or intermittent irritation. It's more often associated with vaginal symptoms in women, and because it can ping-pong between partners, treating both people is the rule.
HSV, adenovirus, and non-sexual irritation
Herpes simplex virus and adenovirus can inflame the urethra, frequently after oral sex, and may come with sores or red eyes (adenovirus). Beyond infections, urethritis can follow non-sexual irritation — an indwelling catheter, friction, or exposure to harsh soaps and spermicides. These aren't "caught" from a partner, which is why mapping the likely cause changes whether your partner needs testing at all.
Symptoms — and the silent reality
When NGU does cause symptoms, the classic trio is urethral discharge (mucoid or pus-like), pain or burning during urination, and itching inside the urethra. It mainly presents in men because the male urethra is long and symptomatic; the same organisms infect women but show up differently, often in the cervix.
The honest catch: a real share of these infections cause nothing you'd notice. You can feel completely fine and still carry — and pass on — chlamydia or M. genitalium. That's the whole argument for routine screening: symptoms are an unreliable smoke alarm here.
How NGU spreads
The infectious causes spread through sexual contact — vaginal, anal, or oral — when mucous membranes or fluids meet. Chlamydia, M. genitalium, and trichomonas all pass this way, and a partner with no symptoms can still transmit. HSV and adenovirus often arrive via oral-genital contact.
The non-sexual causes don't spread between people at all. Catheter-related or irritant urethritis comes from a device or a chemical, not a partner — another reason naming the cause matters before you decide who else needs evaluation.
How NGU is diagnosed
Diagnosis takes two steps: prove the urethra is inflamed, then find the cause. To confirm urethritis, a clinician looks for objective evidence — a Gram stain showing at least two white blood cells per oil-immersion field with no gonococci, or a positive leukocyte esterase test or at least ten white blood cells per high-power field on a first-void urine sample. Then a NAAT (a sensitive DNA test) checks for chlamydia and gonorrhea, with M. genitalium added in persistent cases.
In practice this is undramatic. Most of it comes from a urine cup or a self-collected swab plus a brief exam, and results are usually back in a few days. You can do it free or low-cost at a health department, Planned Parenthood, or a Title X clinic. If you're timing a visit around a specific encounter, check the window first so you don't test too early — see when to test after exposure. To start, you can get tested or compare testing providers.
(The links above are: when to test after exposure, get tested, and compare testing providers.)
Treatment
First-line treatment for NGU is doxycycline 100 mg by mouth twice daily for seven days, now preferred over a single dose of azithromycin because it produces better cure rates and less resistance, especially against M. genitalium. Azithromycin 1 g as a single dose is the alternative. If symptoms persist or recur, the clinician re-confirms urethritis and tests for M. genitalium; when it's positive, the regimen is doxycycline followed by moxifloxacin 400 mg daily for seven days.
Take the full course even after you feel better — stopping early is the classic way infections bounce back. Ask whether your partner needs treating too, so you don't pass it back and forth. For the full breakdown of regimens, see ngu treatment, and if your symptoms don't clear, read about persistent or recurrent ngu.
(Links: ngu treatment and persistent or recurrent ngu.)
| Cause | Sexually transmitted? | Notes |
|---|---|---|
| Chlamydia trachomatis | Yes | Most common identified cause; often silent |
| Mycoplasma genitalium | Yes | Key driver of persistent/recurrent NGU |
| Trichomonas vaginalis | Yes | Parasite; treat both partners |
| HSV / adenovirus | Yes (often oral contact) | May have sores or eye symptoms |
| Catheter / irritant | No | Mechanical or chemical, not transmitted |
| No organism found | — | About half of cases |
Complications if untreated
Left untreated, NGU can move beyond the urethra. In men, the infection can travel to cause epididymitis (inflammation of the coiled tube behind the testicle, which can hurt and threaten fertility), prostatitis (inflammation of the prostate gland, with pelvic pain and urinary trouble), and reactive arthritis (joint inflammation triggered by the infection elsewhere in the body).
Partners face the complications of whatever organism is behind it. With chlamydia, that includes pelvic inflammatory disease (PID) in women — a deeper infection of the uterus and tubes that can scar them and cause infertility or ectopic pregnancy. That risk is the core reason partner treatment isn't optional courtesy; it prevents real harm.
Prevention
- Use condoms every time for vaginal, anal, and oral sex — they lower the risk of the sexually transmitted causes.
- Get tested routinely, since the most common causes often have no symptoms and screening is the only way to catch them.
- Refer all sex partners from the prior sixty days for evaluation, testing, and presumptive treatment effective against chlamydia.
- Finish your full course of medication, and have your partner treated before resuming sex so you don't reinfect each other.
When to see a clinician
See a clinician if you have urethral discharge, burning with urination, or urethral itching — or if a partner was diagnosed with an STI, even when you feel fine. Go back if symptoms persist or return after finishing treatment, because that points toward M. genitalium or a need to recheck the diagnosis. A diagnosis here is common and treatable; clinics manage it daily, and it says nothing about you as a person.