Leukocytes, also known as white blood cells, are a central part of the immune system. They help to protect the body against foreign substances, microbes, and infectious diseases.

These cells are produced or stored in various locations throughout the body, including the thymus, spleen, lymph nodes, and bone marrow.

High leukocyte levels suggest that the body is trying to fight an infection.

Leukocytes travel throughout the body, moving between the organs and nodes and monitoring any potentially problematic germs or infections.

Only very low levels of leukocytes, if any, are normally found in the urine. A high leukocyte content in the urine may indicate an infection or other underlying inflammatory medical problems.

This article will look at five common causes of leukocytes in the urine.

Leukocytes can occur in urine for various reasons.

1. Bladder infections

Urinary tract infectionShare on Pinterest
A high number of leukocytes in the urine may indicate the presence of a urinary tract infection.

A urinary tract infection (UTI) is a common cause of leukocytes in the urine.

A UTI can affect any part of the urinary system, including the bladder, urethra, and kidneys. The lower urinary tract—and especially the bladder and urethra—are common sites for an infection.

A UTI usually happens when bacteria enter the urinary tract through the urethra. They then multiply in the bladder.

Women have a higher risk than men of getting a UTI. Approximately 50–60 percent of women experience a UTI at some point.

If a UTI occurs in the bladder and the person does not seek treatment, the infection can spread to the ureters and kidneys. This can become serious.

2. Kidney stones

A high number of leukocytes can sometimes indicate kidney stones.

Low levels of dissolved minerals and salts are usually present in urine. Those who have high levels of these substances in their urine may develop kidney stones.

Symptoms include:

  • pain
  • nausea
  • vomiting
  • fever
  • chills

If kidney stones travel to the ureters, they can disrupt the flow of urine. If a blockage occurs, bacteria can collect, and an infection can develop.

3. Kidney infection

The number of white blood cells in the urine can go up if there is a kidney infection.

Kidney infections often start in the lower urinary tract but spread to the kidneys. Occasionally, bacteria from other parts of the body reach the kidneys through the bloodstream.

There is a higher chance of developing a kidney infection if a person:

  • has a weak immune system
  • has been using a urinary catheter for some time

4. Urinary system blockage

If a blockage develops in the urinary system, this can lead to:

  • hematuria, or blood in the urine
  • hydronephrosis, or fluid around the kidney or kidneys

An obstruction can result from a traumatic injury, kidney stones, tumors, or other foreign material.

5. Holding in urine

Holding in urine can cause the bladder to weaken, making it difficult to empty.

If urine accumulates in the bladder, the presence of bacteria increases the risk of an infection.

This can raise the levels of leukocytes in the urine.

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White blood cells help all parts of the body fight infection.

These are just a few of the common causes, but there are others. The following can also cause raised levels of leukocytes in the urine:

Leukocytes in the urine cause different symptoms for different people, but there are a few symptoms or signs that suggest leukocytes may be present in the urine.

One of the most visible signs is cloudy or foul-smelling urine. Other signs include frequent urination, a pain or burning sensation when passing urine, or the presence of blood in the urine.

Other symptoms include:

  • shivering and fever
  • lower back and side pain
  • acute pelvic pain
  • nausea or vomiting
  • long-term pelvic pain
  • painful sex

People who notice any of the above symptoms should contact their doctor for further examination.


A urine analysis (urinalysis) is used to screen the urine for abnormalities and may be enough to detect any problems.

People who suspect leukocytes in the urine provide a urine sample that their doctor can analyze in three ways: Visual exam, dipstick test, and microscopic exam.

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A dipstick test will detect any unusual substances in the urine.
  • Visual exam: Technicians examine the appearance of the urine. Cloudiness or an unusual odor may signal an infection or another potential problem. The food that a person eats can also affect urine color.
  • Dipstick test: A thin, plastic stick with strips of chemicals is placed in the urine to detect any abnormalities. The chemicals on the strip will change color to indicate if certain substances are present.
  • Microscopic exam: Drops of urine are examined under a microscope. The presence of leukocytes might be a sign of infection.

Urinalysis is the first stage of testing.

Other tests

If blood or other substances are present in the urine, the physician may perform more tests to identify the cause of the problem.

The problem may be any of the conditions listed above or a more serious noninfectious illness, such as a blood disorder, autoimmune disease, or cancer. The doctor will order additional tests as needed.

Sterile pyuria

It is possible to have white blood cells in the urine without a bacterial infection. Sterile pyuria refers to the persistent presence of white blood cells in the urine when no bacteria are found to be present by laboratory examination.

According to The New England Journal of Medicine, 13.9 percent of women and 2.6 percent of men are affected by this condition. Certain sexually transmitted diseases, viral or fungal infections, or even tuberculosis can cause sterile pyuria.

A correct diagnosis is vital for identifying a path of treatment.

Treatment for leukocytes in the urine depends on the cause and if there is an infection. For some conditions, such as a bacterial UTI, antibiotic therapy will clear up the infection relatively quickly.

For more severe infections or those that will not resolve easily, more in-depth medical treatment may be needed. In some cases, hospitalization may be necessary.

Lifestyle changes can help reduce the symptoms of some conditions that cause leukocytes to enter the urine.

These include:

  • drinking more water
  • urinating when you have to go
  • staying as healthy as you can

Taking acetaminophen, ibuprofen, or prescription drugs may also help to ease pain in the urinary system.