Cloudy urine can be a sign of several sexually transmitted infections — most often chlamydia, gonorrhea, nongonococcal urethritis (NGU), and trichomoniasis. These cause inflammation in the urethra, and the white blood cells and discharge that result can make urine look milky or hazy. But cloudy urine isn't proof of an STI: UTIs, dehydration, and diet do it too. Only a test confirms the cause.
often silent; discharge or burning if anything
discharge and burning; can also hit throat/rectum
urethral discharge or burning with no gonorrhea found
frothy, itchy discharge with an odor
| Item | Value |
|---|---|
| Chlamydia | curable — often silent; discharge or burning if anything |
| Gonorrhea | curable — discharge and burning; can also hit throat/rectum |
| Nongonococcal urethritis (NGU) | curable — urethral discharge or burning with no gonorrhea found |
| Trichomoniasis | curable — frothy, itchy discharge with an odor |
Why STIs turn urine cloudy
The cloudiness usually comes from pyuria — pus in the urine. When bacteria or parasites inflame the urethra (the tube urine passes through), your immune system floods the area with white blood cells. Those cells, along with mucus and discharge, mix into the first part of your urine stream and scatter light, so the sample looks cloudy or stringy rather than clear. Because the inflammation lives in the urethra, the same biology that produces a discharge also produces the haze you see in the toilet.
Which STIs cause cloudy urine
Chlamydia
Chlamydia is caused by the bacterium Chlamydia trachomatis, and most US genital infections are the serovars D–K CDC Chlamydia. It's a famously 'silent' infection: roughly three quarters of infected women and half of infected men feel nothing at all. When symptoms do show, they tend to appear within one to three weeks of exposure — burning on urination, abnormal discharge, and in women bleeding between periods or pelvic pain if it spreads upward. The cloudy-urine clue here is mild and easy to dismiss, which is exactly why so many people never connect the two.
Gonorrhea
Gonorrhea, caused by Neisseria gonorrhoeae, can infect the genitals, rectum, and throat CDC Gonorrhea. In men it classically produces burning urination and a white, yellow, or green penile discharge — that thicker, more purulent discharge is the most common reason a man's urine turns visibly cloudy. Swollen or painful testicles show up less often. Most women have no symptoms, but when present they mirror chlamydia: painful urination, more vaginal discharge, and spotting between periods. The discharge in gonorrhea is often heavier and more colored than in chlamydia, though you can't reliably tell the two apart by eye.
Nongonococcal urethritis (NGU)
NGU is urethritis that isn't gonorrhea — a syndrome, not a single bug CDC Urethritis Tx. Its causes include Chlamydia trachomatis, Mycoplasma genitalium, sometimes Trichomonas, herpes (HSV), or adenovirus, and in about half of cases no organism is ever identified. It mainly affects men and shows up as a mucoid or purulent urethral discharge, painful urination, and urethral itching — the discharge and pyuria together cloud the urine. Some infections are asymptomatic. Because NGU is defined by inflammation rather than a specific pathogen, diagnosing it means proving urethritis is present and then testing for what's driving it.
Trichomoniasis
Trichomoniasis is caused by the protozoan parasite Trichomonas vaginalis and is the most common curable STI CDC Trichomoniasis. About 70% of infected people have no symptoms whatsoever. When women do notice something, it's genital itching, burning, soreness, discomfort urinating, and a clear, white, yellowish, or greenish discharge that may carry a fishy smell. Men more often feel nothing, but can have penile itching or irritation, burning after urinating or ejaculating, and a discharge. Symptoms, when they appear, may show up anywhere from five to 28 days after infection — and sometimes much later, which makes pinning down the exposure tricky.
When cloudy urine is NOT an STI
Plenty of cloudy urine has nothing to do with sex. The usual non-STI culprits are:
- A urinary tract infection (UTI) — bacteria in the bladder or urethra produce pyuria much like an STI does, often with frequency, urgency, and a strong smell.
- Dehydration — concentrated urine looks darker and hazier simply because there's less water diluting it; drinking more usually clears it within hours.
- Kidney stones — crystals and mineral debris can cloud urine and typically come with sharp flank pain.
- Diet — phosphate-rich foods, lots of dairy, or certain supplements can temporarily turn urine milky.
This is the heart of the problem: these causes overlap too much to separate by sight, and several STIs are frequently silent. A test — not the appearance of your urine — is what settles which one (if any) it is.
How to tell them apart
There are patterns clinicians lean on, but none are reliable enough to self-diagnose. A recent unprotected sexual exposure raises the odds of an STI. A discharge that's colored and purulent points toward gonorrhea or NGU; a fishy-smelling, frothy discharge with itching nudges toward trichomoniasis. Burning that comes with urinary frequency and urgency but no discharge looks more like a UTI. A fever, flank pain, or pain on one side can mean a kidney stone or a kidney infection. Honestly, the overlap is the whole point — this is why you usually can't tell from symptoms alone, and why a test turns a guess into an answer.
Side-by-side comparison
| Cause | Typical discharge | Other clues | Often silent? |
|---|---|---|---|
| Chlamydia | Mild/abnormal, may be absent | Burning; symptoms 1–3 weeks after exposure | Yes — ~¾ of women, ~½ of men |
| Gonorrhea | White, yellow, or green; often heavier | Burning; rarely testicular pain | Yes — most women |
| NGU | Mucoid or purulent | Urethral itching; mainly men | Sometimes |
| Trichomoniasis | Clear/white/yellow-green, fishy smell | Itching, soreness; onset 5–28 days | Yes — ~70% |
| UTI (not an STI) | Usually none | Frequency, urgency, strong odor | No |
How it's tested
For all four STIs, a nucleic acid amplification test (NAAT) is the preferred method — it detects the organism's genetic material from a urine sample or a self-collected swab CDC STI Tx Guidelines, 2021. NAAT for gonorrhea has high sensitivity and specificity, and the Trichomonas NAAT is highly accurate as well. NGU is different: diagnosing it first requires objective evidence of urethritis — pus cells on a urine sample or Gram stain — before NAATs sort out the cause. Testing itself is quick: a urine cup, a swab, or a short exam depending on what's suspected, with results usually back in a few days. You can read the full how-to on the get tested page, and check when to test after exposure so you don't test too early to catch an infection.
What to do next
If cloudy urine is paired with a recent exposure, a discharge, or burning, get tested rather than guessing — and if your partner is being treated, you should be tested too. These infections are curable, and treatment is matched to the specific result: see the ngu treatment page for NGU, and learn how a gonorrhea test and trichomoniasis testing & diagnosis confirm those infections. Chlamydia in particular has a high reinfection rate, so plan on a follow-up — the chlamydia reinfection page explains the retesting timeline. Testing is free or low-cost at health departments, Planned Parenthood, and Title X clinics.
Red flags — when to get seen urgently
Cloudy urine alone is rarely an emergency, but get medical care promptly if you have:
- A fever with flank or back pain — this can signal a kidney infection (pyelonephritis), which needs treatment fast.
- Severe one-sided pain or pain that comes in waves — possible kidney stone or, in men, a testicular cause.
- Swollen, painful testicles — possible epididymitis (inflammation of the tube behind the testicle), which can affect fertility if ignored.
- Inability to urinate, blood you can clearly see, or worsening pelvic pain — all reasons to be evaluated the same day.