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White blood cells (WBC)
The immune cells that defend the body against infection. The count rises or falls with infections, inflammation, medicines, and bone marrow conditions.
Other names: White blood cell count, leukocyte countSection: Blood cells
Updated: August 29, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortWhite blood cells are the cells of the immune system. A typical adult count is 4,500–11,000 cells/mcL (4.5–11.0 × 10⁹/L). Above that range is called leukocytosis, below it — leukopenia; both describe the count, not a specific disease. The count is read together with the white cell differential and the rest of the CBC.
Reference ranges
Group
Reference range
Adults
4,500–11,000 cells/mcL (4.5–11.0 × 10⁹/L)
Below the range
under 4,500 cells/mcL (4.5 × 10⁹/L) — leukopenia
Above the range
over 11,000 cells/mcL (11.0 × 10⁹/L) — leukocytosis
These are the common reference values quoted in the MedlinePlus Medical Encyclopedia. Each laboratory sets its own interval, so the range printed on the report is the one that applies.
Check your value
Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.
A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.
What this marker is
White blood cells (leukocytes) are produced in the bone marrow and circulate in the blood and lymphatic system. Their job is defense: they recognize and attack bacteria, viruses, and other foreign material, and they coordinate the body's inflammatory response.
There are five major types — neutrophils, lymphocytes, monocytes, eosinophils, and basophils — and each has its own role. A standard count measures the total; the breakdown by type (the differential) is reported alongside it and often explains which kind of process is driving the total up or down.
The count is almost always part of a complete blood count (CBC), the most common screening panel in medicine. Providers order it for symptoms such as fever or unexplained weakness, to monitor chronic conditions, and to watch how treatments like chemotherapy affect the bone marrow.
A result outside the range does not name a diagnosis by itself. The same elevated count can accompany a routine cold or, less often, a bone marrow disorder, so the number is always read against symptoms, history, and the other CBC lines.
When it is high
Infection, usually bacterialThe bone marrow releases more white cells to fight the invader. This is the most frequent reason for a temporarily high count.
Inflammatory diseaseRheumatoid arthritis, allergic reactions, and similar conditions keep the immune system activated and the count elevated.
Physical or emotional stressSurgery, burns, injury, and intense stress push white cells out of storage pools into the bloodstream within hours.
MedicinesCorticosteroids, epinephrine, beta agonists such as albuterol, lithium, and heparin are known to raise the count.
Smoking and pregnancyBoth are common physiological reasons for a moderately elevated count.
Bone marrow disordersLeukemia and Hodgkin disease produce abnormal white cells in large numbers — the reason an unexplained persistent rise is investigated further.
When it is low
Viral infectionsMononucleosis and certain other viral illnesses temporarily suppress the count or divert cells out of circulation.
Bone marrow problemsDeficiency or failure of the marrow — from infection, tumor, or scarring — reduces production of all blood cells, white cells included.
Cancer treatmentChemotherapy and radiation therapy target fast-dividing cells, and marrow cells divide fast. Counts are monitored throughout treatment.
Autoimmune disordersSystemic lupus and similar conditions can destroy white cells or suppress their production.
Liver or spleen diseaseAn enlarged spleen can trap and destroy white cells faster than they are replaced.
An inherited traitA harmless genetic variant common in people of African ancestry produces a lower baseline count without any disease.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
Current infection or recent illnessCorticosteroids and many other medicinesSmokingPregnancyIntense exercise or stress on the test dayChemotherapy or radiation treatment
How to prepare
No special preparation is needed for a white blood count. If other blood tests are ordered for the same visit, those may require fasting — the order form or the lab will say so. The provider should know about all medicines being taken, including over-the-counter ones, because many of them shift the count.
When a retest makes sense
A single borderline result is often rechecked after a few weeks, once an infection or a course of medicine has passed. During chemotherapy or treatment of a blood disorder the count is repeated on a schedule set by the treating provider, sometimes every few days.
Who usually reviews this result
A result outside the reference range is usually reviewed by: your GP or primary care doctor; a hematologist if a blood disorder is suspected. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: WBCWBC countWhite cell countLeukocyte count
Units and conversion
Measured in: cells/mcL
cells/mcL=× 10⁹/L
cells/mcL ÷ 1,000 = value in × 10⁹/L. Example: 8,000 cells/mcL = 8.0 × 10⁹/L. Results are rounded to 2 decimal places.
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
No. Infection is the most common reason, but stress, smoking, pregnancy, corticosteroids, and inflammatory diseases also raise the count. The differential and the clinical picture separate one cause from another.
What is the difference between WBC and the differential?
The WBC is the total number of white cells. The differential breaks that total into the five cell types — neutrophils, lymphocytes, monocytes, eosinophils, basophils — which points toward the kind of process involved.
Can medicines lower the white count?
Yes. Antibiotics, anticonvulsants, antithyroid drugs, diuretics, clozapine, and chemotherapy medicines are documented causes of a low count, which is why the provider reviews the medicine list before reading the result.
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