Leukocyte Esterase in Urine: Trace, 1+, 2+, 3+ & Abnormal Results

Sample type: Urine

Other names: WBC Esterase, Leuk Est, UA Leuk Est, Leukocyte Esterase UA, Leuk Esterase, Leukocyte Esterase (Urine), Leukoesterase, Leukest, U-Leukocyte Esterase, F Leukocyte Esterase, F WBC Esterase, WBC Esterase UR, WBC Esterase Urine, Leukocyte Esterase Urine Qualitative, Leukocyte Esterase Urine POC, UA Leuk Est POC, POC Leukocyte Esterase, Leuk Est UR, Leuk Esterase UR, Leukocyte Esterase UR, Leukocytes Esterase UA, WBC Esterase 01, WBC (Leukocyte) Esterase POC, Leukocyte Est POC, WarningAbnormal WBC Esterase

Written May 14, 2026

Updated September 8, 2026

By Healthmatters Editorial Team

Peer-reviewed sources

Negative

No leukocyte esterase detected. This is the expected, normal finding in healthy urine and means no significant white blood cell activity was picked up in the sample.

Trace

A small amount of leukocyte esterase was detected. Trace results are frequently caused by sample contamination or mild irritation rather than infection, particularly when there are no urinary symptoms and nitrites are negative. A repeat clean-catch midstream sample is the usual next step before any clinical action.

1+ (Small)

A mild elevation. This may reflect early infection, contamination, or non-bacterial inflammation. Whether it matters depends on your symptoms, your nitrite result, and the white blood cell count on microscopy — not on this value alone. Asymptomatic 1+ results with negative nitrites often represent contamination.

2+ (Moderate)

A moderate amount of leukocyte esterase. Combined with urinary symptoms such as burning, urgency or frequency, this is more suspicious for active infection, and a urine culture is typically recommended to confirm bacteria and guide treatment. Without symptoms it still warrants review alongside nitrites and microscopy.

3+ (Large)

A high concentration of leukocyte esterase. With urinary symptoms this is strongly consistent with an active urinary tract infection or urinary inflammation, and culture is usually indicated. Fever or flank pain alongside this result should prompt medical review, as it may point to kidney involvement.

AT A GLANCE

Leukocyte esterase is an enzyme produced by white blood cells (WBCs); its presence in urine indicates WBCs are present in the urinary tract
A negative result is normal — the expected finding in healthy urine
Any result above negative — Trace, 1+, 2+, or 3+ — is flagged abnormal and indicates white blood cell activity in the urinary tract
Abnormal does not automatically mean infection — leukocyte esterase must be interpreted alongside nitrites, urine WBC count, bacteria, and symptoms
The most common cause of an abnormal result is a urinary tract infection (UTI), but contamination, STIs, kidney inflammation, and other causes are possible
Trace and 1+ results without symptoms often represent contamination or mild irritation and may not require treatment
2+ or 3+ with symptoms (burning, urgency, frequency, fever, flank pain) typically warrant urine culture and clinical evaluation
Reference ranges and reporting formats vary by laboratory and analyzer. All results should be interpreted by a clinician.

QUICK REFERENCE

Leukocyte Esterase Urine — Result Tiers

Negative        =  Normal. No significant WBC activity detected.
Trace           =  Very low WBC signal. Often contamination. Repeat if asymptomatic.
1+ (Small)      =  ~15–75 LEU/µL. Mild elevation. Context-dependent.
2+ (Moderate)   =  ~75–250 LEU/µL. Moderate WBC level. Culture if symptomatic.
3+ (Large)      =  ≥250 LEU/µL. High WBC level. Likely infection if symptomatic.

WHAT TO DO NEXT

Based on your result and symptom status:

Negative — Normal. No action required.
Trace or 1+, no symptoms — Likely contamination. Repeat with a clean-catch midstream sample. No treatment needed if asymptomatic in most cases.
Trace or 1+, with symptoms — Report to your doctor. A urine culture may be appropriate even at low levels when burning, urgency, or pelvic pressure are present.
2+ or 3+, with symptoms — Likely UTI. Urine culture is typically recommended to confirm bacteria and guide antibiotic choice.
2+ or 3+, no symptoms — Check whether the sample was a clean-catch. Repeat testing. Discuss with your doctor — asymptomatic bacteriuria management depends on your situation.
Any level with fever, chills, or flank/back pain — Seek same-day or urgent medical evaluation. These symptoms suggest possible kidney infection (pyelonephritis).
Positive leukocyte esterase, negative nitrites — Does not rule out infection. See the section below.

WHAT IS LEUKOCYTE ESTERASE?

Leukocyte esterase is an enzyme produced by neutrophils — the white blood cells most involved in fighting bacterial infections. When WBCs are present in urine, they release leukocyte esterase, which is detected by the chemically treated dipstick pad used in a standard urinalysis (UA).

The test is a screening component of the urinalysis. It does not identify the specific cause of WBC presence, the type of bacteria involved, or whether antibiotics are needed. It signals that white blood cells are present and that further evaluation may be warranted. A urine culture remains the gold standard for confirming bacterial infection and identifying the causative organism.

Results are reported semi-quantitatively as Negative, Trace, 1+ (Small), 2+ (Moderate), or 3+ (Large). Some analyzers report a numeric value in leu/µL (also written LEU/µL, leu/ul, or LEU/UL) alongside or instead of the +/trace scale. The numeric thresholds correspond approximately to: 75 LEU/µL = 1+, 250 LEU/µL = 2+, 500 LEU/µL = 3+, though exact breakpoints vary by analyzer model.

HOW TO READ YOUR RESULT

Result	Approx. WBC level	What it means
Negative	<5 WBCs/µL	Normal. Expected in healthy urine.
Trace	~5–15 WBCs/µL	Low-level signal. Often contamination or mild non-infectious irritation. Repeat clean-catch appropriate if asymptomatic.
1+ (Small)	~15–75 LEU/µL	Mild elevation. May reflect early infection, contamination, or non-bacterial inflammation. Significance depends on symptoms and other UA findings.
2+ (Moderate)	~75–250 LEU/µL	Moderate elevation. More likely to represent active infection with symptoms. Urine culture typically recommended.
3+ (Large)	≥250 LEU/µL	High WBC concentration. Strongly consistent with UTI or urinary inflammation when symptoms present. With fever or flank pain, seek prompt evaluation.

Numeric reporting (LEU/µL): some labs report a numeric value. These map to the same tiers: 75 LEU/µL ≈ 1+; 250 LEU/µL ≈ 2+; 500 LEU/µL ≈ 3+. The tier label is more reliable than the exact number for clinical interpretation because thresholds vary by analyzer.

COMMON PHRASES SEEN ON LAB REPORTS

LEUKOCYTE ESTERASE, URINE
LEUKOCYTE ESTERASE UA
WBC ESTERASE
WBC ESTERASE ABNORMAL
UA LEUK EST
UA LEUK EST ABNORMAL
LEUK EST
LEUK ESTERASE
LEUKOCYTE ESTERASE URINE ABNORMAL
WBC ESTERASE TRACE
WBC ESTERASE TRACE ABNORMAL
WBC ESTERASE 1+
WBC ESTERASE 1+ ABNORMAL
WBC ESTERASE 2+
WBC ESTERASE 2+ ABNORMAL
WBC ESTERASE 3+
WBC ESTERASE 3+ ABNORMAL
LEUKOCYTE ESTERASE 1+
LEUKOCYTE ESTERASE 2+
LEUKOCYTE ESTERASE 3+
LEUKOCYTE ESTERASE TRACE
LEUKOCYTE ESTERASE URINE TRACE ABNORMAL
LEUKOCYTE ESTERASE URINE 1+
LEUKOCYTE ESTERASE URINE 2+
LEUKOCYTE ESTERASE URINE 3+
LEUKOCYTE ESTERASE URINE LARGE
LEUKOCYTE ESTERASE 250
LEUKOCYTE ESTERASE 500
LEUKOCYTE ESTERASE 75
LEUKOCYTE ESTERASE URINE 250
LEUKOCYTE ESTERASE URINE 500
LEUKOCYTE ESTERASE URINE 75
75 LEU/UL ABNORMAL
250 LEU/UL
500 LEU/UL
LEUKOCYTE ESTERASE UA TRACE
LEUKOCYTE ESTERASE UA 1+
LEUKOCYTE ESTERASE UA 2+
LEUKOCYTE ESTERASE UA 3+
LEUKOCYTE ESTERASE UA LARGE
WARNINGABNORMAL WBC ESTERASE
UA LEUK EST POC ABNORMAL
F WBC ESTERASE
F LEUKOCYTE ESTERASE
LEUKEST
LEUKOESTERASE
U-LEUKOCYTE ESTERASE
LEUKOCYTE ESTERASE UR ABNORMAL
WBC ESTERASE UR 2+
WBC ESTERASE UR 3+
LEUKOCYTE ESTERASE URINE SMALL ABNORMAL
LEUKOCYTE ESTERASE URINE MODERATE ABNORMAL
LEUKOCYTE ESTERASE URINE LARGE ABNORMAL
LEUKOCYTE ESTERASE, UA, POC
WBC (LEUKOCYTE) ESTERASE POC

All of these labels refer to the same test. "WBC esterase" and "leukocyte esterase" are interchangeable — WBC stands for white blood cell, and leukocyte is the clinical term for white blood cell.

WHAT DOES ABNORMAL LEUKOCYTE ESTERASE MEAN?

An abnormal leukocyte esterase result means white blood cells were detected in your urine above the normal negative threshold. This signals inflammation or infection somewhere in the urinary tract.

Urinary tract infection (UTI) is the most common cause. Bacteria trigger an immune response that floods the urine with WBCs. Leukocyte esterase is often one of the first indicators.

Sample contamination — particularly in females — is the most common non-infectious explanation, especially for Trace and 1+ results. Vaginal discharge, skin flora, or improper collection technique can introduce WBCs into the sample without any urinary tract pathology. Clean-catch midstream technique matters.

Sexually transmitted infections — chlamydia, gonorrhea, and trichomonas cause urethral inflammation that produces a characteristic pattern: positive leukocyte esterase, negative nitrites, and negative standard urine culture. STI testing requires specific assays, not a standard UA.

Kidney infection (pyelonephritis) produces higher WBC counts alongside fever, chills, and flank pain. This is a more serious presentation requiring prompt treatment.

Non-infectious causes include interstitial cystitis, kidney stones, urethral irritation, recent catheterization, and bladder procedures.

The level of elevation alone does not determine the cause. Urine culture is the definitive test for bacterial infection.

WHAT DOES TRACE LEUKOCYTE ESTERASE MEAN?

A trace leukocyte esterase result means a very low level of WBC enzyme activity was detected — above a clean negative but below the 1+ threshold. It is the most frequently misunderstood urinalysis result.

In an asymptomatic person — no burning, urgency, frequency, fever, or pain — a trace result is most often due to sample contamination or very mild non-infectious irritation. In most cases, repeat testing with a properly collected clean-catch sample returns negative. Treatment is rarely indicated.

A trace result with UTI symptoms is more clinically significant. If symptoms are present, do not dismiss it — report to your doctor for a decision on whether culture is warranted.

A trace result alongside positive nitrites is more concerning than trace with negative nitrites, since nitrites suggest bacterial metabolic activity even at low WBC counts.

LEUKOCYTE ESTERASE POSITIVE, NITRITES NEGATIVE: WHAT DOES IT MEAN?

This is one of the most common urinalysis patterns and one of the most frequently misinterpreted. A positive leukocyte esterase with negative nitrites does not rule out infection.

Nitrites are produced when gram-negative bacteria (E. coli, Klebsiella) convert urinary nitrates. The nitrite test only detects bacteria that perform this conversion, and only when urine has adequate bladder dwell time (typically 4+ hours).

Positive leukocyte esterase with negative nitrites can mean:

Non-nitrite-producing organisms — gram-positive bacteria (Staphylococcus saprophyticus, Enterococcus), Pseudomonas, and STI-associated pathogens do not convert nitrates. UTI caused by these organisms produces WBCs without nitrites.
Insufficient bladder dwell time — dilute urine or frequent voiding can produce falsely negative nitrites even with bacteria present.
Non-bacterial inflammation — STIs, interstitial cystitis, kidney stones, or contamination. WBCs present without bacterial UTI.
Early infection — bacterial load not yet sufficient to produce detectable nitrites.

When leukocyte esterase is positive and nitrites are negative, urine microscopy and/or culture are the appropriate next steps.

WHAT DO 75, 250, AND 500 LEU/µL MEAN?

These numeric values are the quantitative version of the semi-quantitative tier scale. They reflect the same tiers with numeric precision, though exact breakpoints vary by analyzer.

75 LEU/µL corresponds to the lower boundary of the 1+ (Small) range. Results reported as "75 leu/ul abnormal" indicate mild WBC elevation. In an asymptomatic patient, repeat clean-catch testing is appropriate. In a symptomatic patient, clinical assessment is warranted.

250 LEU/µL corresponds to the 2+ (Moderate) range. With UTI symptoms — burning, urgency, frequency — this level strongly suggests active infection. Urine culture is typically indicated.

500 LEU/µL corresponds to the 3+ (Large) range. High WBC concentration. With symptoms, strongly consistent with active UTI. With fever and flank pain, seek prompt evaluation for possible kidney infection.

IS A POSITIVE LEUKOCYTE ESTERASE ALWAYS A UTI?

No. Leukocyte esterase indicates WBCs are present in urine — it does not identify the cause. Several non-UTI causes are common:

Sample contamination — the most frequent non-infectious cause, especially at Trace and 1+ levels in females
STIs — chlamydia, gonorrhea, trichomonas produce urethral WBCs with a characteristic pattern (positive leukocyte esterase, negative nitrites, negative routine culture)
Interstitial cystitis — chronic bladder inflammation without bacterial infection
Kidney stones — irritation produces WBCs in urine
Recent instrumentation — catheterization, cystoscopy
Vaginal discharge — direct sample contamination

A urine culture is required to confirm bacterial UTI and guide treatment.

RELATED TESTS AND NEXT STEPS

Leukocyte esterase is one component of the urinalysis. Read it alongside:

Nitrite, Urine — positive nitrites + positive leukocyte esterase strongly suggests gram-negative bacterial UTI
WBC Count, Urine (Microscopy) — direct microscopic count; gold standard for confirming pyuria
Bacteria, Urine — direct microscopic detection; combined with positive leukocyte esterase is highly predictive of UTI
Urine Culture — identifies the organism and antibiotic sensitivities; required to guide treatment
RBC, Urine — blood alongside positive leukocyte esterase raises concern for stones, hemorrhagic cystitis, or glomerulonephritis
Protein, Urine — if protein is also elevated, kidney disease should be considered
Squamous Epithelial Cells, Urine — high squamous cells confirm sample contamination, which contextualizes a positive leukocyte esterase

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Frequently Asked Questions

What does leukocyte esterase in urine mean?

Leukocyte esterase in urine means white blood cells are present in the urinary tract. It is an enzyme released by WBCs as part of an immune response to inflammation or infection. Any result above negative is flagged abnormal and most commonly suggests a urinary tract infection, though contamination, STIs, and non-infectious causes are also possible.

What does abnormal leukocyte esterase mean?

Abnormal leukocyte esterase means WBCs were detected above the normal negative threshold. The most common cause is a urinary tract infection. However, sample contamination, sexually transmitted infections, kidney inflammation, and non-bacterial bladder irritation can also produce abnormal results. The finding must be interpreted alongside nitrites, microscopy, and symptoms.

What does WBC esterase abnormal mean?

WBC esterase abnormal is the same result as abnormal leukocyte esterase — the two names refer to the same test. White blood cells were detected in the urine sample above the normal threshold. The interpretation and next steps are identical.

What does trace leukocyte esterase in urine mean?

Trace leukocyte esterase means a very low WBC signal was detected — above negative but below the 1+ threshold. In an asymptomatic person, this most often reflects sample contamination and does not require treatment. With UTI symptoms present, a trace result is clinically significant and should be discussed with a doctor.

What does leukocyte esterase 1+ mean?

Leukocyte esterase 1+ (also called Small) corresponds to approximately 15–75 LEU/µL and represents a mild elevation. It may reflect early infection, contamination, or non-bacterial inflammation. Whether it requires treatment depends on symptoms, nitrite results, and microscopy findings. Asymptomatic 1+ results with negative nitrites often represent contamination.

What does leukocyte esterase 2+ mean?

Leukocyte esterase 2+ (also called Moderate) corresponds to approximately 75–250 LEU/µL and indicates moderate WBC concentration. With UTI symptoms — burning, urgency, frequency — this level is more suspicious for active infection. Urine culture is typically recommended when symptomatic.

What does leukocyte esterase 3+ mean?

Leukocyte esterase 3+ (also called Large) corresponds to approximately 250–500 LEU/µL or above and indicates a high WBC concentration. With symptoms this is strongly consistent with active UTI or urinary inflammation. With fever or back/flank pain, seek prompt medical evaluation for possible kidney infection.

What does WBC esterase trace mean?

WBC esterase trace is the same as trace leukocyte esterase — a very low WBC signal above negative. In an asymptomatic patient it usually reflects contamination and does not require treatment. Repeat clean-catch testing is appropriate.

What does 75 LEU/µL mean on a urine test?

75 LEU/µL corresponds to the 1+ (Small) threshold — a mild elevation of leukocyte esterase. Results reported as "75 leu/ul abnormal" indicate low-level WBC activity. With no symptoms, this often represents contamination; with UTI symptoms, clinical evaluation is appropriate.

What does 250 LEU/µL mean on a urine test?

250 LEU/µL corresponds to the 2+ (Moderate) tier — a meaningful WBC elevation. With UTI symptoms, this level suggests active infection and a urine culture is typically indicated. Without symptoms, repeat testing with a properly collected clean-catch sample is appropriate.

What does 500 LEU/µL mean on a urine test?

500 LEU/µL corresponds to the 3+ (Large) tier — a high WBC concentration. With symptoms this is strongly consistent with active UTI. With fever and back or flank pain, seek prompt medical evaluation for possible kidney infection.

What does leukocyte esterase positive but nitrites negative mean?

Leukocyte esterase positive with negative nitrites is a common urinalysis pattern that does not rule out infection. Not all bacteria produce nitrites — gram-positive organisms and STI-associated pathogens typically do not. This pattern can also reflect contamination, STIs, interstitial cystitis, or early infection with low bacterial load. Urine microscopy or culture is the appropriate next step.

Is a trace of leukocyte esterase in urine normal?

A trace result is flagged abnormal on most lab reports, but in an asymptomatic person it often reflects sample contamination rather than true infection. Trace leukocyte esterase without UTI symptoms typically does not require treatment. A repeat clean-catch midstream sample usually resolves the finding.

What does leukocyte esterase large mean?

Leukocyte esterase large is equivalent to 3+ — a high WBC concentration corresponding to approximately 250–500 LEU/µL or above. With UTI symptoms, this strongly suggests active infection. With fever or back/flank pain, seek prompt medical evaluation.

What does ua leuk est abnormal mean?

"UA leuk est abnormal" is a shortened lab format for "urinalysis leukocyte esterase abnormal." It means the leukocyte esterase component of your urinalysis was above the normal negative threshold — white blood cells were detected in the sample.

Can leukocyte esterase be positive without a UTI?

Yes. Leukocyte esterase can be positive without a UTI. Sample contamination is the most common non-infectious cause, especially at Trace and 1+ levels in females. Sexually transmitted infections cause urethral WBCs with a specific pattern — positive leukocyte esterase, negative nitrites, negative routine culture. Interstitial cystitis, kidney stones, and recent catheterization also produce WBCs in urine without bacterial infection.

What is the normal range for leukocyte esterase in urine?

The normal result for leukocyte esterase in urine is Negative. Any result above negative — Trace, 1+, 2+, or 3+ — is flagged abnormal. There is no numeric "normal range" in the traditional sense; the test is qualitative and the reference result is Negative.

What does WBC esterase 2+ abnormal mean?

WBC esterase 2+ abnormal indicates moderate leukocyte esterase activity at approximately 75–250 LEU/µL. This is more likely to represent active infection than a trace or 1+ result. With UTI symptoms, a urine culture is typically recommended.

What does WBC esterase 3+ abnormal mean?

WBC esterase 3+ abnormal indicates a high WBC concentration at approximately 250–500 LEU/µL or above. With symptoms this is strongly associated with active UTI. With fever or flank pain, seek same-day medical evaluation for possible kidney infection.

Is positive leukocyte esterase always serious?

No. Trace and 1+ results without symptoms are frequently due to sample contamination and are not clinically serious. Higher levels with symptoms are more likely to represent infection and warrant evaluation. The result must always be interpreted alongside symptoms and other urinalysis findings — the level alone does not determine severity.

Can leukocyte esterase be high during pregnancy?

Yes. Leukocyte esterase may be positive during pregnancy because UTIs and asymptomatic bacteriuria are more clinically important in pregnancy. Pregnant patients with abnormal urine findings should discuss results with their clinician, since urine culture is often used to confirm infection and guide treatment.

Clinical Sources & References

All our content is backed by peer-reviewed studies, academic research, and trusted medical sources. We’re committed to accuracy and transparency — see our editorial policy for details.

IDSA 2019 Clinical Practice Guideline Update for the Management of Asymptomatic Bacteriuria

Infectious Diseases Society of America · 2019 View source ↗
Urinalysis: a comprehensive review

American Family Physician · 2005 View source ↗
The urine dipstick test useful to rule out infections. A meta-analysis of the accuracy

BMC Urology · 2004 View source ↗
Urinary Tract Infection Basics

CDC · 2024 View source ↗

Article Review Log

Last reviewed August 1, 2026

Originally published May 14, 2026

Reviewed by HealthMatters Editorial Team

Written by Healthmatters Editorial Team

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Leukocyte Esterase in Urine: Trace, 1+, 2+, 3+ & Abnormal Results

AT A GLANCE

QUICK REFERENCE

WHAT TO DO NEXT

WHAT IS LEUKOCYTE ESTERASE?

HOW TO READ YOUR RESULT

COMMON PHRASES SEEN ON LAB REPORTS

WHAT DOES ABNORMAL LEUKOCYTE ESTERASE MEAN?

WHAT DOES TRACE LEUKOCYTE ESTERASE MEAN?

LEUKOCYTE ESTERASE POSITIVE, NITRITES NEGATIVE: WHAT DOES IT MEAN?

WHAT DO 75, 250, AND 500 LEU/µL MEAN?

IS A POSITIVE LEUKOCYTE ESTERASE ALWAYS A UTI?

RELATED TESTS AND NEXT STEPS

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Frequently Asked Questions

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Related Health Conditions

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