Getting lab results can be confusing—especially when something unexpected shows up. If you’ve been told there are white blood cells in your urine, you might be wondering what that means, whether it’s serious, and what to do next.
This finding, often noted as “pyuria” on a test report, doesn’t always point to something urgent. But it does suggest that your urinary tract might be dealing with inflammation or infection, and it’s worth looking into the possible causes.
Let’s explore why white blood cells (WBCs) show up in urine, what symptoms might come with them, and how doctors figure out what’s really going on.
What Are White Blood Cells, and Why Are They in Urine?
White blood cells are part of your body’s immune system. Their job is to detect and fight off infections or anything that shouldn’t be in your body. Normally, urine should be sterile—meaning it shouldn’t contain bacteria, viruses, or immune cells.
So when white blood cells appear in your urine, it means your immune system is reacting to something in the urinary tract, kidneys, or bladder. The presence of these cells alone doesn’t give a full diagnosis, but it tells your doctor where to start digging.
Common Causes of White Blood Cells in Urine
1. Urinary Tract Infection (UTI)
This is the most common reason. Bacteria (usually E. coli) enter the urethra and multiply, triggering an immune response.
Typical symptoms:
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Burning or stinging while urinating
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Frequent or urgent need to pee
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Cloudy or strong-smelling urine
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Lower abdominal pain or pressure
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Mild fever
If left untreated, a lower UTI can travel up to the kidneys and become more serious.
2. Kidney Infection (Pyelonephritis)
This occurs when a UTI moves beyond the bladder. White blood cells increase significantly as the kidneys try to fight off the bacteria.
Additional signs may include:
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Flank or back pain (on one or both sides)
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High fever and chills
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Nausea or vomiting
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Fatigue or confusion (especially in older adults)
3. Interstitial Cystitis (IC)
A chronic condition that causes bladder inflammation without an actual infection. Some people with IC may have WBCs in their urine without bacteria present.
Symptoms include:
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Ongoing bladder pain or pressure
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Frequent urination (even at night)
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Discomfort during sex
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Flare-ups triggered by certain foods or stress
4. Kidney Stones
Stones can irritate the urinary tract lining, leading to inflammation and the presence of white blood cells—even without infection.
Look for:
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Severe pain in the back or side
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Blood in the urine
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Nausea or vomiting
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Pain that comes and goes in waves
5. Contamination During Collection
Sometimes, white blood cells show up in urine samples simply because of contamination from the skin or vaginal discharge—especially in women. This isn’t dangerous but may lead to a false impression of infection.
Doctors often repeat the test with a clean-catch sample to get clearer results.
6. Sexually Transmitted Infections (STIs)
Some infections like chlamydia or gonorrhea can cause elevated WBCs in the urine, especially in younger, sexually active individuals.
Symptoms might include:
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Discharge from the urethra or vagina
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Pain during urination or sex
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Pelvic pain
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Testicular swelling in men
In these cases, further testing with a urine culture or swab is essential for accurate diagnosis.
How Is It Diagnosed?
Finding white blood cells in urine is usually done through a urinalysis, a simple test that examines urine under a microscope or using a dipstick. The lab might also measure leukocyte esterase, an enzyme that suggests WBC activity.
Depending on the findings, your doctor may order:
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Urine culture (to identify bacteria)
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Imaging tests (like ultrasound or CT if kidney stones are suspected)
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STI testing if sexually transmitted infections are a possibility
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Blood work to look for signs of systemic infection
When Should You See a Doctor?
If white blood cells show up in your urine but you don’t feel sick, your doctor might just repeat the test to confirm it wasn’t a fluke. But if you’re feeling unwell or notice any of the following, you should follow up promptly:
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Painful urination
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Blood in the urine
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Fever, chills, or back pain
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Cloudy, foul-smelling urine
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Any change in bladder habits that persists
White blood cells in urine aren’t always a cause for alarm—but they do tell a story. Sometimes it’s a simple UTI that clears up with antibiotics. Other times, it’s a signal that your body is fighting something deeper. Either way, it’s a clue worth listening to. Your urine may be trying to speak up—make sure you don’t miss what it’s saying.