Several sexually transmitted infections can cause cloudy urine, most commonly gonorrhea, chlamydia, trichomoniasis, and mycoplasma genitalium. The cloudiness happens because your immune system floods the urinary tract with white blood cells to fight the infection, a condition called pyuria. Discharge from the urethra can also mix with urine and change its appearance.
How STIs Make Urine Cloudy
When an STI infects the urethra (the tube urine passes through), your body sends white blood cells to the area to attack the bacteria or parasite. Those white blood cells end up in your urine. Pyuria is diagnosed when there are 10 or more white blood cells per cubic millimeter of urine, and at that concentration, urine looks visibly cloudy or milky rather than its normal clear-to-pale-yellow color.
Urethral discharge is the other factor. Gonorrhea and chlamydia both trigger inflammation in the urethra that produces discharge, which can range from thin and watery to thick and yellowish. Even when you’re not actively noticing discharge, small amounts can mix into urine and cloud it. This is especially common with the first urination of the day, when discharge has had time to accumulate overnight.
Gonorrhea
Gonorrhea is the STI most strongly associated with cloudy urine because it tends to produce the heaviest urethral discharge. In men, symptoms often start within five days of exposure and typically include thick, yellow-green discharge, burning during urination, and cloudy urine. Women may develop symptoms within 10 days, though many women with gonorrhea have mild or no symptoms at all, which means the infection can progress without obvious urinary changes.
Chlamydia
Chlamydia causes a milder form of urethritis than gonorrhea, but it still produces enough inflammation and discharge to cloud urine in many cases. Symptoms usually appear 5 to 14 days after exposure. The discharge tends to be thinner and more watery than gonorrhea’s, so the urine cloudiness may be subtler. Chlamydia is also frequently asymptomatic, particularly in women, where up to 70% of infections produce no noticeable symptoms.
Trichomoniasis
Trichomoniasis is caused by a parasite rather than bacteria, and it can produce cloudy or frothy discharge that affects urine appearance. Symptoms may show up anywhere from 5 to 28 days after exposure, a wider window than most bacterial STIs. In women, trichomoniasis often causes a greenish-yellow vaginal discharge with a strong odor, along with burning during urination. Men with trichomoniasis frequently have no symptoms, but when they do, urethral irritation and mild discharge can make urine appear cloudy.
Mycoplasma Genitalium
Mycoplasma genitalium (often called Mgen) is a lesser-known but increasingly recognized cause of urethritis. It’s one of the most common causes of non-gonococcal urethritis, meaning urethral inflammation not caused by gonorrhea. In men, Mgen can cause penile discharge, pain while urinating, and pain during ejaculation. In women, it can produce abnormal vaginal discharge and a burning sensation during urination. The discharge and inflammation from Mgen can cloud urine in the same way gonorrhea and chlamydia do, though symptoms tend to be milder.
STI vs. UTI: Telling the Difference
Cloudy urine is also a hallmark symptom of urinary tract infections, which are far more common than STIs. Since the two can look similar, knowing the distinguishing features helps you figure out what you’re dealing with.
Signs that point more toward a UTI include needing to urinate more frequently than usual, a burning sensation while peeing, mild lower abdominal or pelvic pain, and no abnormal genital discharge. Blood in your urine is more common with UTIs, though it can occasionally show up with certain STIs too.
Signs that point more toward an STI include abnormal discharge from the penis or vagina, genital blisters or rash, pain during intercourse, itchiness around the genitals, swollen lymph nodes in the groin, or heavier and more painful periods. If you’re noticing both cloudy urine and any of these symptoms, an STI is more likely than a straightforward UTI. It’s also worth knowing that an untreated STI can lead to a UTI, so both can be present at the same time.
Getting Tested
If your urine has turned cloudy and you’ve had recent unprotected sexual contact, STI testing is straightforward. Most clinics can test for gonorrhea and chlamydia with a simple urine sample or swab, and results typically come back within a few days. Trichomoniasis testing is also done via swab or urine. Mycoplasma genitalium testing is less routinely offered but can be specifically requested, especially if initial tests for gonorrhea and chlamydia come back negative but symptoms persist.
Because chlamydia, gonorrhea, and trichomoniasis can all be present without obvious symptoms, cloudy urine may be one of the only early clues. All three are treatable with antibiotics or antiparasitic medication, and earlier treatment reduces the risk of complications like pelvic inflammatory disease or spreading the infection to partners.