NGU (nongonococcal urethritis) and chlamydia overlap. NGU means inflammation of the urethra that isn't caused by gonorrhea, and chlamydia is one of its most common causes. So chlamydia can be NGU; the term "NGU" is used when a man has urethritis but the specific organism hasn't been pinned down. A test is what separates them.
treated like chlamydia
~1.65M US cases/yr; cured with doxycycline
| Item | Value |
|---|---|
| Nongonococcal urethritis (NGU) | curable — treated like chlamydia |
| Chlamydia | curable — ~1.65M US cases/yr; cured with doxycycline |
What each one is
Nongonococcal urethritis (NGU)
NGU is a syndrome. It describes urethritis — inflammation of the tube that carries urine out of the body — that lab testing shows is not caused by Neisseria gonorrhoeae. The "non-specific" label exists because several organisms can produce the same picture: Chlamydia trachomatis, Mycoplasma genitalium, and sometimes Trichomonas, herpes simplex virus, or adenovirus CDC STI Guidelines, 2021. In about half of NGU cases, no organism is identified at all. NGU is often the diagnosis you land on after a negative gonorrhea and chlamydia test, when the inflammation is real but the cause stays unnamed.
Chlamydia
Chlamydia is caused by one specific bacterium, Chlamydia trachomatis, and most U.S. genital infections are serovars D–K. It's the most-reported STI in the country — roughly 1.65 million cases in 2023, around 492 per 100,000 people, a number that's stayed roughly flat across recent years CDC AtlasPlus, 2023. When chlamydia infects a man's urethra and produces inflammation, it is a cause of NGU. Chlamydia has a name and a specific test; NGU is the broader bucket that includes it.
Symptoms compared
For anyone trying to self-diagnose, the symptoms look almost identical, because chlamydia is one of the things causing NGU in the first place.
NGU classically shows up in men as urethral discharge (which may be thin and mucoid or thicker and pus-like), painful urination, and an itching or irritated feeling inside the urethra. Some infections cause no symptoms at all.
Chlamydia is famously quiet. About three-quarters of infected women and about half of infected men notice nothing CDC Chlamydia Fact Sheet. When women do have symptoms, they may see abnormal vaginal discharge and burning when urinating; if the infection spreads upward, it can cause lower abdominal or low-back pain, fever, pain during sex, and bleeding between periods — signs the infection has reached the upper reproductive tract. In men, symptomatic chlamydia produces the same discharge-and-burning picture that defines NGU.
How to tell them apart
You can't, by feel. The symptoms overlap enough that a man with discharge and painful urination cannot know whether it's chlamydia, gonorrhea, M. genitalium, or no identifiable organism. The discriminating features are all in the lab:
- NGU is a diagnosis of what it's NOT. A clinician confirms urethritis exists and rules out gonorrhea — what's left is "nongonococcal."
- Chlamydia is a diagnosis of what it IS. A positive NAAT for Chlamydia trachomatis names the organism directly.
- The two can be the same event. A man diagnosed with NGU whose chlamydia test comes back positive simply has chlamydial urethritis — both labels fit.
- NGU is largely a male-presentation term. Chlamydia is diagnosed across all anatomies and sites, including cervical, rectal, and throat infection.
NGU vs chlamydia: side-by-side
| NGU | Chlamydia | |
|---|---|---|
| What it is | A syndrome — urethritis not caused by gonorrhea | A specific bacterium (Chlamydia trachomatis) |
| Cause | Chlamydia, M. genitalium, others; about half have no organism found | Always C. trachomatis |
| Typical symptoms | Discharge, painful urination, urethral itch (mainly men) | Often none; discharge/burning when present |
| How it's diagnosed | Objective urethritis + negative gonorrhea | Positive NAAT for chlamydia |
| First-line treatment | Doxycycline, twice daily for 7 days | Doxycycline, twice daily for 7 days |
| Relationship | Chlamydia is a leading cause of NGU — they overlap, not oppose | |
Testing
Diagnosing NGU takes two steps. First, a clinician confirms inflammation is objectively present — typically a Gram stain showing at least two white blood cells per oil-immersion field with no gonococci, or a positive leukocyte esterase or at least ten white cells per high-power field on a first-void urine sample. Second, the same visit runs a NAAT (nucleic acid amplification test) for chlamydia and gonorrhea, plus M. genitalium testing in persistent cases. Confirming the inflammation matters because treating discharge without objective urethritis leads to unnecessary antibiotics.
Chlamydia testing is simpler: NAAT is the recommended method for both genital and extragenital (rectal, throat) infection CDC Chlamydial Infections. In practice, that means a urine sample, a self-collected swab, or a quick exam depending on what's suspected. You can get tested at most clinics, and it's free or low-cost at health departments, Planned Parenthood, and Title X clinics. If you're testing because of a specific encounter, check when to test after exposure first — testing too early can miss an infection that hasn't reached detectable levels yet.
Treatment compared
Here the two converge almost completely. First-line treatment for both NGU and chlamydia is doxycycline 100 mg by mouth twice daily for 7 days CDC STI Tx Guidelines, 2021. The 2021 guidelines moved away from the older single-dose azithromycin because doxycycline clears infection more reliably — in a randomized trial of rectal chlamydia, doxycycline cured every case (100%) versus 74% with single-dose azithromycin. For NGU, doxycycline is also favored for fewer resistance concerns; single-dose azithromycin 1 g remains an alternative when doxycycline can't be used.
The paths diverge when symptoms don't resolve. Persistent or recurrent NGU calls for re-confirming the urethritis and testing for M. genitalium — and if it's positive, a course of doxycycline followed by moxifloxacin 400 mg daily for 7 days. For chlamydia, treating partners prevents the ping-pong of reinfection: in a landmark trial, expedited partner therapy (giving patients medication to deliver to partners) cut persistent or repeat infection, with the biggest benefit for gonorrhea (3% vs 11%) NEJM EPT trial. Full dosing and follow-up details live on the ngu treatment page, and the timeline for re-testing after treatment is covered under chlamydia reinfection.
Can you have more than one at once?
Yes. Because NGU is a syndrome and chlamydia is a single organism, having chlamydia is one way to have NGU. Co-infection with multiple STIs is also common — a man with chlamydial urethritis can also carry gonorrhea or M. genitalium, so testing covers more than one organism at the same time. A negative chlamydia test in someone with confirmed urethritis doesn't mean nothing's wrong; it means the cause is one of the other NGU organisms, or one of the roughly half of cases where no organism is found Rectal chlamydia RCT, CID.
When to see a clinician
See a clinician promptly if you have urethral or vaginal discharge, burning when you urinate, urethral itching, or pelvic pain — especially after a new partner or unprotected sex. Don't wait for symptoms to get worse; chlamydia in particular is often silent, and untreated infection can spread. Bring partners into the conversation, since treating them stops reinfection. If you have no symptoms but a partner tested positive, get tested anyway — you may be carrying an infection that feels like nothing.