Leukocytes in urine are the body's most direct indicator of inflammation or infection in the urinary tract. They are also one of the most frequently encountered abnormal findings in a routine urinalysis — and one of the easiest to misread if the sample wasn't collected correctly.
Here's what leukocytes in urine mean, what counts as normal, and when a high result requires medical attention.
What Are Leukocytes in Urine (Leukocyturia)
Leukocytes (white blood cells) are immune cells the body sends to sites of infection or inflammation. Under normal conditions, only minimal numbers pass into urine.
When inflammation or infection is present in the urinary tract or kidneys, large numbers of leukocytes migrate to the affected area — and some end up in the urine. This is called leukocyturia (or pyuria when there are many).
On lab reports it appears as Leukocytes, LEU, WBC (urine), or in the microscopy section as WBC per high-power field (HPF).
Normal Leukocyte Levels in Urine
| Method | Normal Range |
|---|---|
| Dipstick (qualitative) | Negative or trace |
| Microscopy (men) | up to 5 per HPF |
| Microscopy (women) | up to 10 per HPF (slightly higher) |
| Nechiporenko test | up to 2,000 per mL |
| 24-hour test | up to 2,000,000 per day |
A mildly elevated count in women without symptoms is often due to sample contamination, not actual inflammation.
Causes of High Leukocytes in Urine
Infectious / inflammatory (most common):
- Cystitis — bladder infection; the most common cause in women
- Urethritis — urethral inflammation, often from STIs (chlamydia, gonorrhoea)
- Pyelonephritis — bacterial kidney infection; pronounced leukocyturia
- Prostatitis — prostate inflammation in men can cause leukocyturia
- Renal tuberculosis — "sterile" leukocyturia without standard bacterial growth
Non-infectious:
- Kidney stones — stones irritate and damage the urinary lining, triggering inflammation
- Glomerulonephritis — immune-mediated inflammation of kidney filters
- Interstitial nephritis — kidney tissue inflammation, often drug-induced
- Autoimmune conditions — systemic lupus erythematosus and others
False causes (contamination):
- Not cleaning the genital area before collection
- Menstruation
- Non-sterile container
- Sample sitting too long before delivery to the lab
Causes of Low Leukocytes in Urine
Absent leukocytes is the normal and desired result. There is no clinical significance to "low" leukocytes in urine.
Symptoms of Elevated Leukocytes
With cystitis or urethritis: burning or stinging on urination, frequent urge to urinate, feeling of incomplete emptying, cloudy urine, occasionally blood in urine.
With pyelonephritis: lower back pain (usually one-sided), high fever (38–40°C), chills, nausea, severe fatigue.
With asymptomatic leukocyturia: no symptoms at all — detected only on routine testing. Common in elderly patients and those with chronic kidney disease.
How to Prepare for the Test
Correct collection is critical — errors are the most common cause of falsely elevated leukocytes:
- Clean the genital area thoroughly without soap (or with mild soap) before collection
- Collect a mid-stream morning urine sample — discard the first 2–3 seconds
- Use a sterile pharmacy container
- Women should use a tampon during collection to prevent vaginal discharge contamination
- Do not collect during menstruation
- Deliver to the lab within 1–2 hours — leukocytes deteriorate quickly
Leukocytes and Nitrites in Urine: What the Combination Means
Leukocytes are almost always assessed alongside nitrites in a urinalysis:
| Result | Interpretation |
|---|---|
| Leukocytes ↑, nitrites + | High probability of bacterial infection (UTI, pyelonephritis) |
| Leukocytes ↑, nitrites − | Non-bacterial inflammation: chlamydia, fungi, stones, autoimmune |
| Leukocytes normal, nitrites + | Possible contamination or very early infection |
To confirm infection and choose the right antibiotic, doctors order a urine culture with sensitivity testing.
When to See a Doctor
See a GP or urologist if:
- Leukocytes are elevated on a repeat test collected correctly
- You have infection symptoms: pain, burning, fever, back pain
- Leukocyturia is combined with protein or nitrites in urine
- You are pregnant — urinary infections during pregnancy always require treatment
For high fever and back pain (signs of pyelonephritis) — seek medical attention the same day.
Understand Your Full Urinalysis in Seconds
Leukocytes are just one of dozens of urinalysis markers. The full picture comes from the combination of leukocytes, nitrites, protein, red blood cells, specific gravity, and urine colour.
Upload your report to LabReadAI — AI will analyse all urinalysis values together, identify patterns pointing to infection or inflammation, and suggest which specialist to see.