White blood cells in a urine test often point to inflammation somewhere in the urinary tract. A urinary tract infection is a common cause, but the result can also occur with kidney stones, urethritis, prostatitis, contamination, and other conditions.
Updated for a U.S. audience in 2026
If a urinalysis shows leukocytes in urine, it means white blood cells have been detected directly or through a urine dipstick marker called leukocyte esterase. That finding often raises suspicion for a urinary tract infection, or UTI, but it does not prove that bacteria are present.
The result makes the most sense when it is interpreted together with symptoms, nitrites, bacteria, microscopic findings, urine culture, and the way the sample was collected. A positive leukocyte result without urinary symptoms may need a different approach from leukocytes found with burning, fever, or flank pain.
Key Takeaways
- Leukocytes are white blood cells, and increased numbers in urine usually signal infection or inflammation.
- A UTI is a common cause, particularly when there is burning, urgency, frequent urination, lower abdominal discomfort, cloudy urine, or strong odor.
- A positive leukocyte esterase result is a screening finding rather than a final diagnosis.
- Leukocytes can also occur with kidney infection, kidney stones, urethritis, some STIs, prostatitis, sample contamination, and sterile pyuria.
- Negative nitrites do not rule out a UTI because not every UTI-causing bacterium produces nitrites.
- Treatment depends on the cause. Antibiotics are not automatically needed for every positive urine dipstick.
What Are Leukocytes in Urine?
Leukocytes are white blood cells that help the immune system respond to infection and inflammation. When the bladder, urethra, kidneys, prostate, or nearby tissues become inflamed, white blood cells may move into the urine.
An increased number of white blood cells in urine is often called pyuria. Laboratories may report actual white blood cells under a microscope or use categories such as trace, small, moderate, or large leukocyte esterase.
What Does Positive Leukocyte Esterase Mean?
Leukocyte esterase is an enzyme associated with certain white blood cells. A dipstick test can detect it quickly and is commonly included in a urinalysis.
A positive result suggests white blood cells are present, but it does not identify the cause by itself. MedlinePlus explains that a positive leukocyte esterase test may indicate a UTI and is often followed by microscopic examination for white blood cells and other signs of infection.
A leukocyte esterase test is also different from a urine culture. A culture looks for bacteria that grow from the urine sample and may help determine which antibiotic is likely to work when bacterial infection is suspected.
What Causes Leukocytes in Urine?
1. Urinary Tract Infection
A bladder infection is one of the most common explanations. When bacteria infect the urinary tract, the immune system sends white blood cells to the area.
Typical symptoms include burning during urination, frequent or intense urges to urinate, lower abdominal discomfort, cloudy or bloody urine, and a stronger-than-usual odor.
When clinicians investigate a possible bladder infection, urinalysis can check for white blood cells and other abnormalities, while a urine culture may identify bacteria. NIDDK describes how bladder infections in adults are diagnosed with urinalysis and urine culture.
2. Kidney Infection
A kidney infection can develop when bacteria travel upward from the bladder. Leukocytes may appear in the urine along with bacteria, blood, or other abnormal findings.
Fever, chills, nausea, vomiting, and pain in the back, side, or groin are more concerning than simple bladder symptoms and deserve prompt medical attention.
3. Kidney Stones
A stone can irritate the urinary tract and cause inflammation, which may increase white blood cells. Stones can also occur together with infection.
Sharp pain in the back, side, lower abdomen, or groin, blood in the urine, nausea, and urinary urgency are common clues. Fever or chills with suspected stone symptoms needs urgent evaluation because infection with obstruction can become serious.
4. Urethritis and Sexually Transmitted Infections
Inflammation of the urethra can produce leukocytes even when a routine bacterial urine culture is negative. Depending on symptoms and exposure, clinicians may consider gonorrhea, chlamydia, trichomoniasis, and other infections.
Burning, urethral itching, genital discharge, pelvic discomfort, or a recent sexual exposure are reasons to consider STI testing rather than assuming the result is an ordinary bladder infection.
5. Prostatitis
In men, inflammation or infection of the prostate can produce white blood cells in urine. Symptoms may include pelvic or perineal pain, painful urination, frequent urination, difficulty emptying the bladder, painful ejaculation, or fever.
6. Sample Contamination
Not every positive result comes from the urinary tract itself. Vaginal secretions, menstrual blood, skin cells, or poor collection technique can introduce white blood cells into a urine specimen.
If the laboratory result does not match the symptoms, a clinician may request a repeat clean-catch midstream sample before deciding on treatment.
What Is Sterile Pyuria?
Sterile pyuria means white blood cells are present in urine but a standard urine culture does not grow the usual bacteria. The term does not necessarily mean nothing is wrong.
Possible explanations include recent antibiotic use, urethritis or an STI, kidney stones, urinary inflammation, certain medications, contamination, and less common infectious or inflammatory conditions. Persistent sterile pyuria should be investigated rather than repeatedly treated with antibiotics without a clear diagnosis.
Leukocytes Positive but Nitrites Negative: Is It Still a UTI?
Yes. Nitrite tests detect a chemical change produced by certain bacteria. Some UTI-causing bacteria do not make nitrites, and frequent urination may not leave urine in the bladder long enough for nitrites to build up.
Leukocytes plus positive nitrites make a bacterial UTI more likely, but leukocytes with negative nitrites still need to be interpreted using symptoms and, when appropriate, microscopy or culture.
| Urine test pattern | What it may suggest | Possible next step |
| Leukocytes + / Nitrites + | Bacterial UTI becomes more likely | Review symptoms and consider culture |
| Leukocytes + / Nitrites – | UTI still possible; other causes also possible | Microscopy, culture, or repeat sample may help |
| Leukocytes – / Nitrites + | Possible bacterial UTI | Interpret with symptoms and confirm as needed |
| Both negative | UTI becomes less likely | Further evaluation if symptoms remain strong |
Can Leukocytes Make Urine Look Cloudy?
They can contribute to cloudiness when present in larger numbers, especially with bacteria, mucus, crystals, or other inflammatory material. However, individual white blood cells are microscopic and cannot be identified simply by looking into the toilet.
Visible specks, strings, flakes, or sediment can have many causes. Twiage Health’s guide to white particles in urine explains how mucus, crystals, infection, genital discharge, and stone material can change urine appearance.
For male-specific causes, including semen, prostatitis, urethritis, and urinary sediment, see white stuff floating in urine in men.
How Many Leukocytes in Urine Are Normal?
Reference ranges vary by laboratory and collection method. Some laboratories report white blood cells per high-power field, while others report only leukocyte esterase categories.
Use the reference interval printed on your own laboratory report rather than an internet cutoff. A small abnormality may mean something different in a person with no symptoms than in someone with fever, burning, or severe flank pain.
Can You Have Leukocytes in Urine With No Symptoms?
Yes. Leukocytes may be found during routine testing even when a person feels well. Contamination, asymptomatic bacteriuria, a recently treated infection, or another inflammatory cause may be responsible.
Leukocytes alone do not automatically justify antibiotics. Pregnancy, planned urinary procedures, and certain medical conditions can change how an asymptomatic result is handled, so the clinical context matters.
How Do Doctors Find the Cause?
- Urinalysis: Checks leukocyte esterase, nitrites, blood, protein, and other chemical findings.
- Microscopy: Counts white blood cells and may show red blood cells, bacteria, crystals, or epithelial cells.
- Urine culture: Looks for bacterial growth and may help guide antibiotic treatment.
- STI testing: May be appropriate when urethritis or sexual exposure is part of the picture.
- Imaging: Ultrasound or CT may be used when stones, obstruction, or another structural problem is suspected.
How Are Leukocytes in Urine Treated?
There is no treatment aimed at the leukocytes themselves. Treatment targets the condition causing the immune response.
A bacterial bladder or kidney infection may require antibiotics. Kidney stones are treated according to their size, location, symptoms, and whether infection or obstruction is present. An STI needs treatment specific to the infection, while a contaminated sample may only require repeat testing.
Do not use leftover antibiotics simply because an at-home urine strip shows leukocytes. The wrong antibiotic may fail to treat the cause, cause side effects, and interfere with later testing.
When Should You Seek Medical Care?
- fever or chills with urinary symptoms
- moderate to severe back or side pain
- vomiting or inability to keep fluids down
- pregnancy with fever or significant urinary symptoms
- visible blood or blood clots in urine
- inability to urinate or rapidly worsening urinary symptoms
- new genital discharge or significant STI exposure
Common Questions About Leukocytes in Urine
Does positive leukocytes always mean a UTI?
No. A UTI is common, but stones, urethritis, STIs, prostatitis, contamination, and sterile pyuria can also cause white blood cells in urine.
Can dehydration cause leukocytes in urine?
Dehydration can concentrate urine, but it is not usually the main explanation for persistent pyuria. An unexpected result may need a repeat properly collected sample.
Can a yeast infection affect a leukocyte urine test?
Vaginal inflammation or discharge can contaminate a urine specimen and contribute to a positive result. A repeat clean-catch sample may help when the finding is unclear.
Should leukocytes in urine always be treated with antibiotics?
No. Antibiotics are appropriate when bacterial infection is diagnosed or strongly suspected. A positive dipstick without supporting symptoms or findings may need confirmation first.
Can leukocytes be present without bacteria?
Yes. This is often called sterile pyuria and can occur with STIs, stones, recent antibiotics, medications, contamination, and other inflammatory conditions.
The Bottom Line
Leukocytes in urine usually mean white blood cells have entered the urine because part of the urinary tract is inflamed. A bacterial UTI is a common explanation, especially when leukocytes occur with burning, urgency, frequency, nitrites, bacteria, or cloudy urine, but the test result alone does not prove infection.
The right next step depends on symptoms and the rest of the urinalysis. A clean-catch repeat sample, microscopy, urine culture, STI testing, or imaging may be needed when the cause is unclear. Seek prompt medical care when urinary symptoms occur with fever, flank pain, vomiting, pregnancy, visible blood, or difficulty urinating.
Medical Note
This article is for general educational purposes and is not a substitute for medical advice, diagnosis, or treatment. Persistent abnormal urine findings or significant urinary symptoms should be evaluated by a qualified health care professional.