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Kidney

Leukocytes in urine in women: bladder infection, contamination and pregnancy

The immune system protects the body against foreign invaders, and leukocytes, the white blood cells, take part in that. The urine of a healthy woman holds so few that a test strip does not see them; with an inflammation of the bladder, a kidney or the urethra they do end up in the urine.

A urinary tract infection can cause pain when passing urine, cloudy urine or newly getting up at night to pass urine, although the UK guidance calls those symptoms not completely reliable in women under 65. Only a urine test shows whether immune cells are in the urine.

Laboratories expect negative as the result; above that the score runs through trace to +, ++ and +++. A positive score can also arise from contamination during collection.

Doctor's Assessment Included

Leukocytes are white blood cells, the cells that fight infection; the leukocyte strip looks in the urine for an enzyme they release, and normally the result is negative.

  • A positive leukocyte strip fits inflammation of the kidneys, bladder or urinary tract, but it is not a diagnosis: nitrite, symptoms and a urine culture count too.
  • The leukocyte strip misses some infections: in studies it was positive in 72 to 97 percent of proven urinary tract infections.
  • Above 65 the leukocyte strip is less reliable, because bacteria and white blood cells in the urine without infection become more common.

Reference Ranges

Expected result Negative

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Urine Leukocytes: what this test measures

The leukocyte strip carries a pad for leukocyte esterase: an enzyme found in neutrophils, a type of white blood cell.

Contamination during collection can make the pad falsely positive. According to the UK primary-care guidance, midstream urine and holding the labia apart may help to limit contamination.

Urine Leukocytes: why this value matters

Leukocytes in the urine can point to an inflammation of the bladder, a kidney or the urethra, and a urine culture can show whether bacteria are involved.

In pregnancy, the UK guidance advises always offering women with bacteria in the urine, which a urine culture or the test strip can show, antibiotics straight away, even without symptoms, because such bacteria are a risk factor for a kidney infection and premature delivery. The same guidance advises not routinely treating bacteria in the urine without symptoms in women who are not pregnant, because that does not reduce death or illness and can cause harm.

Urine Leukocytes: how the blood test works

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Urine Leukocytes: when is testing worthwhile?

When a woman under 65 has only pain when passing urine, only cloudy urine or only new night-time urination, the UK guidance advises a test strip for leukocytes and nitrite. With two or more of those symptoms, a urinary tract infection in women under 65 is already likely according to the guidance.

Urine Leukocytes: symptoms of a high or low value

Low Levels

Negative is the normal result for leukocytes in urine, but a negative strip does not fully rule out an infection: according to a 2005 review in American Family Physician, the strip in studies reacted in 72 to 97 percent of urinary tract infections confirmed by a culture. Ongoing symptoms after a negative leukocyte strip are a reason to see a doctor. In pregnant women under 65 with a suspected urinary tract infection, the UK guidance does advise sending a urine culture.

High Levels

Fever, shivering and pain in the flank, together with a positive leukocyte strip, may point to a kidney infection and are then a reason to see a doctor.

In pregnancy such a kidney infection calls for extra caution: the UK guidance names pregnancy, in people aged 16 and over, as a reason to consider hospital admission for an acute kidney infection.

Urine Leukocytes: causes of a low or high value

What lowers the value

  • Vitamin C

    Vitamin C in the urine can make the leukocyte strip falsely negative.

  • Concentrated urine, glucose or protein

    Very concentrated urine, or a lot of glucose or protein in the urine, can make the leukocyte strip falsely negative.

  • Some antibiotics

    Some antibiotics, such as nitrofurantoin, tetracycline and gentamicin, can make the leukocyte strip falsely negative.

What raises the value

  • Urinary tract infection

    In a bladder or other urinary tract infection, leukocytes can often be detected in the urine; together with a positive nitrite test they suggest a urinary tract infection.

  • A sexually transmitted infection such as chlamydia

    A sexually transmitted infection such as chlamydia can put leukocytes in the urine while an ordinary urine culture grows nothing.

  • Inflammation without bacterial growth

    Leukocytes in the urine with no growth in the culture can fit, among other things, an earlier course of antibiotics, a catheter, urinary stones or a bladder tumour.

  • Bacteria and white cells without infection in older adults

    Above 65, more and more people have bacteria and white blood cells in the urine without an infection; this can make the leukocyte strip positive, and antibiotics do not help then.

  • Contaminated urine sample

    Urine that was not caught cleanly can make the leukocyte strip falsely positive.

Urine Leukocytes: lifestyle and this value

After a positive leukocyte strip with a negative culture, a chlamydia test can be one of the possible next steps, because in sterile pyuria the UK guidance lists chlamydia among the causes to consider, especially between 16 and 24.

Urine Leukocytes: frequently asked questions

I have leukocytes in my urine but no bladder infection. What can it be?

Leukocytes in urine without a bladder infection can come from contamination during collection. When the culture stays negative while there are leukocytes, called sterile pyuria, the UK guidance names chlamydia and other vaginal infections, among others, as a possible cause.

What do leukocytes in urine mean during pregnancy?

Leukocytes in urine during pregnancy can, as outside pregnancy, point to an inflammation of the urinary tract. When you are pregnant and the test strip or a culture points to bacteria in the urine, discuss it with your midwife or doctor, even without symptoms.

Is chlamydia a cause of leukocytes in urine?

Yes, chlamydia can give leukocytes in urine while an ordinary urine culture grows nothing. The UK guidance names chlamydia as a cause to consider in sterile pyuria, leukocytes in the urine while the culture grows nothing, especially between 16 and 24. A chlamydia test is a separate test for that.

Urine Leukocytes: sources

  1. Hitzeman N, Greer D, Carpio E. Office-Based Urinalysis: A Comprehensive Review. Am Fam Physician 2022;106(1):27-35B. (retrieved 2026) aafp.org
  2. Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review. Am Fam Physician 2005;71(6):1153-1162. (retrieved 2026) aafp.org
  3. UK Health Security Agency. Diagnosis of urinary tract infections: quick reference tools for primary care, updated 7 July 2025. (retrieved 2026) gov.uk

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