Leukocytes

Do you have a fever, become ill frequently, or has your doctor told you that your “white blood cells” are elevated? Leukocytes are white blood cells that defend the body against infections. The test shows how many you have in your blood and helps detect infection, inflammation or a disorder of blood cell production.

Who the test is intended for

• for fever, a sore throat, cough or other signs of infection;
• people who frequently develop infections or whose wounds heal slowly;
• for a follow-up when a previous report showed a high or low white blood cell count;
• people taking medicines that can lower the white blood cell count, such as some medicines for thyroid disease, rheumatic diseases or epilepsy;
• during and after chemotherapy, as instructed by the oncologist;
• as part of a general health check.

What the test reveals

Leukocytes are produced in the bone marrow. When infection or inflammation occurs in the body, the bone marrow produces more of them and sends them into the blood, so the count rises. In some viral infections, with certain medicines or in bone marrow diseases, the count may fall.

The test provides the total white blood cell count. The white blood cell count is also part of the complete blood count, which includes an automated differential blood count: the proportions of neutrophils, lymphocytes, monocytes, eosinophils and basophils. When cell appearance needs closer examination, a separate differential blood count (DKS), a manual examination of a blood smear under a microscope, is performed.

What the test involves and how to prepare

Blood is taken from a vein, and collection takes a few minutes. You do not need to fast unless glucose or lipids are being measured at the same time. Avoid strenuous physical activity the day before. State which medicines you take, especially corticosteroids, as they can raise the white blood cell count.

What your result means

In adults, the white blood cell count is approximately 3,4 to 9,7 × 10⁹/L. Children have higher values, and the age-specific interval printed on your report applies. A slight deviation is often temporary and insignificant. The doctor interprets the report alongside symptoms, an examination and other results, such as CRP.

• Elevated leukocytes (leukocytosis) most often accompany bacterial infection or inflammation. They also rise after exertion, with stress, smoking, pregnancy and corticosteroids. A very high count or immature cells in the blood require further investigation, sometimes by a haematologist.
• Low leukocytes (leukopenia) occur in viral infections, with some medicines, autoimmune diseases, vitamin B12 or folic acid deficiency and, less often, bone marrow diseases. Some healthy people have a persistently slightly lower count without any disease.

If you know that your white blood cell count, particularly neutrophils, is very low and you develop a fever, contact a doctor immediately or call 194 or 112.

How to arrange testing

You can have blood collected without an appointment or referral at one of our branches across Croatia (listed on the Contact page). Prices for all tests and panels are available in the price list. For children with an infection, the Children’s panel, which includes a blood count, CRP and urinalysis, is a practical option.

Frequently asked questions

What do elevated white blood cells mean?

Most often infection or inflammation, but also exertion, stress or smoking. The doctor assesses whether an infection is more likely bacterial or viral alongside the differential blood count and CRP. Read more in the article Inflammatory markers in blood.

Are leukocytes in blood the same as leukocytes in urine?

No. Leukocytes in urine are measured in urinalysis and most often suggest urinary tract inflammation. This test measures leukocytes in the blood.

Can the white blood cell count show leukaemia?

Leukaemia may markedly change the white blood cell count, but the count alone is not a diagnosis. The vast majority of abnormalities have more common and less serious causes, such as infection. When the blood count suggests a blood disorder, the doctor requests a blood smear examination and a haematologist’s opinion.

When should the test be repeated after an infection?

The white blood cell count usually returns to the reference range once the infection has resolved. If it was outside the range, the doctor usually repeats the test after a few weeks, when you are well.