Leukocyte Esterase Blood Test

Leukocyte esterase is an enzyme that lives inside white blood cells. White blood cells are your body's infection fighters. When these cells break down in your urine, they release this enzyme. A urine test can detect it and flag a possible infection.

This test looks for infection or inflammation anywhere in your urinary tract. That includes your bladder, urethra, ureters, or kidneys. A positive result means white blood cells are present. It does not pinpoint exactly where the problem is. But it tells you that something needs attention.

• Detect urinary tract infections before they spread to your kidneys
• Investigate burning, pain, or frequent urination symptoms
• Monitor recurring UTIs to identify root causes
• Evaluate cloudy, foul-smelling, or bloody urine
• Catch kidney infections early when fever or back pain appears
• Screen for inflammation in the urinary system

A positive leukocyte esterase test usually comes with UTI symptoms. These include burning or pain when you urinate. You may feel a frequent and urgent need to pee. Your urine might look cloudy or smell stronger than usual. Lower belly or pelvic discomfort is common. Sometimes you see blood in your urine.

If the infection spreads to your kidneys, symptoms get more serious. You might develop a fever or chills. Back or flank pain appears on one or both sides. Nausea and vomiting can occur. A negative result typically means no infection symptoms are present. Your urinary tract is working as it should.

Several factors can trigger UTIs or affect leukocyte esterase levels. Dehydration concentrates your urine and makes infections more likely. Holding urine for too long allows bacteria to multiply. Sexual activity can introduce bacteria into the urinary tract. Poor hygiene practices increase infection risk. Some people have incomplete bladder emptying, which leaves bacteria behind.

Imbalances in your urinary or vaginal microbiome make recurring infections more common. Certain antibiotics or birth control methods can disrupt these healthy bacteria. Diet matters too. High sugar intake can feed harmful bacteria. Caffeine and alcohol irritate the bladder. Constipation puts pressure on the bladder and affects emptying.

• Drink 8 to 10 glasses of water daily to flush bacteria from your urinary tract
• Urinate every 3 to 4 hours and completely empty your bladder each time
• Pee soon after sexual activity to clear bacteria from the urethra
• Wipe front to back after using the bathroom to prevent bacterial spread
• Avoid holding urine when you feel the urge to go
• Wear breathable cotton underwear and avoid tight pants
• Reduce sugar and processed foods that feed harmful bacteria
• Consider cranberry supplements or D-mannose for UTI prevention
• Add probiotic-rich foods like yogurt and kefir to support healthy bacteria
• Limit caffeine and alcohol, which irritate the bladder lining
• Address constipation through fiber intake and hydration
• Avoid harsh soaps or douches that disrupt vaginal pH balance

Leukocyte esterase is an enzyme released by white blood cells (neutrophils) when they accumulate in urine. A positive result means white blood cells are present, which usually signals inflammation or infection in the urinary tract.

Positive (abnormal) results are commonly caused by:

• Urinary tract infection (UTI) — the most frequent cause, especially in women. Bacteria in the bladder trigger an immune response that sends white blood cells into the urine
• Kidney infection (pyelonephritis) — a more serious infection where bacteria travel from the bladder to the kidneys
• Kidney stones — stones can irritate the urinary lining and attract white blood cells even without bacteria
• Interstitial cystitis — chronic bladder inflammation that produces white blood cells without bacterial infection
• Sexually transmitted infections — chlamydia and gonorrhea can cause urethral inflammation that shows up as positive leukocyte esterase
• Sample contamination — vaginal discharge or improper collection technique can produce a false positive

A negative result means no significant white blood cells were detected. This is the expected finding in healthy individuals.

When leukocyte esterase is positive alongside nitrites, the likelihood of a bacterial UTI is very high. When positive without nitrites, a non-bacterial cause is more likely.

If you tested positive and received antibiotics for a UTI, your provider typically requests a follow-up urinalysis 7 to 14 days after completing treatment to confirm the infection has cleared.

For recurrent UTIs (three or more per year), periodic retesting every 3 to 6 months or at the first sign of symptoms helps catch infections early.

A single positive result without symptoms may be a false positive from sample contamination. A clean-catch midstream repeat test within 1 to 2 weeks can confirm or rule out a real finding.

Persistent positive results without infection may warrant further evaluation for conditions like interstitial cystitis or kidney stones.