Cloudy pee usually means something harmless, like not drinking enough water or eating certain foods. But it can also signal a urinary tract infection, kidney stones, or other conditions worth checking out. The cloudiness comes from particles suspended in your urine: crystals, white blood cells, bacteria, discharge, or excess protein.
A single episode of cloudy urine that clears up on its own is rarely a concern. When it persists for more than a day or two, or shows up alongside pain, fever, or a strong odor, it’s worth figuring out the cause.
Dehydration Is the Most Common Cause
When you’re not drinking enough fluids, your urine becomes more concentrated. Minerals and waste products that are normally diluted enough to stay invisible start clumping together, giving your pee a cloudy or murky look. The color also shifts from pale yellow toward dark amber. If you drink a few extra glasses of water and your urine clears up within hours, dehydration was likely the culprit.
Urinary Tract Infections
UTIs are one of the most common medical causes of cloudy urine. When bacteria invade the urinary tract, your immune system sends white blood cells to fight the infection. Those white blood cells, along with dead tissue and bacteria, form pus. Even a small amount of pus mixed into urine makes it look cloudy, and it can also turn the color whitish, yellowish, or even slightly green.
Cloudiness from a UTI almost never shows up alone. You’ll typically also notice a burning sensation when you pee, a frequent or urgent need to go, and urine that smells unusually strong or foul. If the infection reaches the kidneys, you may develop flank pain (in your side or lower back) and fever. Blood in the urine can also appear with UTIs, sometimes making it look pink or reddish on top of the cloudiness.
Mineral Crystals in Your Urine
Your urine naturally contains dissolved minerals. Under certain conditions, those minerals can form tiny crystals that scatter light and make your pee look cloudy. The most common types are calcium oxalate, calcium phosphate, and uric acid crystals. These can form in perfectly healthy people, especially after eating foods rich in oxalates (like spinach, beets, and nuts), consuming a lot of dairy, or eating large amounts of animal protein.
Crystals forming occasionally is normal. But when they form consistently over time, they can clump together into kidney stones. Kidney stones themselves can cause cloudy urine, often accompanied by sharp pain in the side or lower back, pain during urination, and sometimes blood in the urine.
Vaginal Discharge
For people with vaginas, one of the most frequent and least worrisome explanations is simply vaginal discharge mixing with urine during collection. Normal discharge varies throughout the menstrual cycle and can easily make a urine sample look cloudy, even when there’s nothing wrong with the urinary tract itself. This is common enough that labs specifically check urine samples for signs of contamination before diagnosing an infection. If a sample contains a lot of skin cells from the vaginal area, the test is typically repeated with a cleaner catch.
Sexually Transmitted Infections
Several STIs cause discharge from the urethra that mixes with urine and creates a cloudy appearance. Gonorrhea is the most well-known, often producing a thick, yellowish or greenish discharge. Chlamydia can cause a similar but usually milder discharge. Trichomoniasis is another possibility.
With STIs, the cloudiness tends to be most noticeable in the first pee of the morning. You may also experience burning during urination, unusual discharge between bathroom trips, or irritation around the opening of the urethra. Some STIs, particularly chlamydia, can cause cloudy urine with few or no other obvious symptoms.
Prostate Problems in Men
Prostatitis, or inflammation of the prostate gland, is a recognized cause of cloudy urine in men. The prostate sits just below the bladder and surrounds the urethra, so when it’s inflamed, inflammatory fluid and white blood cells can leak into the urinary stream. Semen that enters the urethra after ejaculation (called retrograde ejaculation) can also cause temporary cloudiness.
Prostatitis often comes with pelvic pain, difficulty urinating, a weak urine stream, and sometimes pain during or after ejaculation. It can be caused by bacterial infection or by chronic inflammation without a clear infectious cause.
Pregnancy
Pregnant people notice cloudy urine more often for several overlapping reasons. Increased vaginal discharge during pregnancy frequently mixes with urine samples. UTIs are also more common during pregnancy because hormonal changes and the growing uterus can slow urine flow and make it easier for bacteria to take hold. Preeclampsia, a serious pregnancy complication involving high blood pressure, can cause protein to spill into the urine, which creates a foamy or cloudy appearance. If cloudy urine during pregnancy comes with swelling in the hands or face, headaches, or vision changes, that combination needs prompt medical evaluation.
Less Common Causes
Chronic kidney disease can gradually impair the kidneys’ ability to filter properly, allowing protein and other substances to pass into the urine and cloud it. This tends to develop slowly and may not cause noticeable symptoms until the disease has progressed significantly.
A rare condition called chyluria produces dramatically milky white urine. It happens when lymphatic fluid, which normally carries fats from your digestive system, leaks into the urinary tract through an abnormal connection. This is most often caused by parasitic infections common in tropical regions and is extremely unusual in North America and Europe.
Certain medications can also cause crystal formation in the urine. The crystals vary in size and shape depending on the specific drug, but the visual result is the same: urine that looks hazy or opaque rather than clear.
What Your Doctor Checks For
A standard urinalysis can identify most causes of cloudy urine quickly. The test measures several things at once. It checks for white blood cells, which point toward infection or inflammation. It looks for nitrites, a chemical byproduct that certain bacteria produce, which strongly suggests a UTI when present. It also checks for protein, glucose, blood, and other substances that shouldn’t be there in significant amounts.
Normal urine has no detectable nitrites, no significant white blood cells, and no glucose. When white blood cells and nitrites both show up positive alongside bacteria, a UTI is the most likely diagnosis. If the sample also contains a lot of skin cells, it may indicate the sample was contaminated during collection, and you’ll be asked to provide another one.
When Cloudy Urine Needs Attention
Cloudy urine that resolves after drinking more water, or that appears once and doesn’t return, is generally not a concern. The situations that warrant a closer look are when cloudiness persists for several days, or when it’s accompanied by other symptoms: pain or burning during urination, fever, back or side pain, blood in the urine, or unusual discharge.
Blood in the urine deserves specific attention. When it accompanies pain, it’s commonly from a UTI or kidney stone. Painless blood in the urine is less common but can indicate more serious problems, including bladder or kidney cancer, and should always be evaluated.