Home Biomarkers Total Leukocyte Count

Total Leukocyte Count

CBC Biomarker

Sample Needed

Collection Type: Blood

Body System

Related System: CBC

Overview

Total Leukocyte Count (TLC), also called the total white blood cell (WBC) count, measures the total number of white blood cells in a volume of blood. White blood cells are key components of the immune system that fight infection and mediate inflammation. The test screens for infection, inflammation, immune disorders, bone marrow problems and some blood cancers. Symptoms that commonly prompt testing include fever, chills, recurrent or severe infections, unexplained bruising, fatigue, weight loss, or prolonged sore throat. Normal values vary with age (newborns and young children normally have higher counts; elderly may have lower baselines), pregnancy (mildly elevated), and transiently with stress, exercise, time of day and smoking; gender differences are minimal.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: included in the CBC (complete blood count).
Indications: fever, signs of infection, unexplained bleeding/bruising, persistent fatigue, suspected inflammation or hematologic disease.
Diagnoses/monitoring: detects infection/inflammation, monitors response to therapy, screens for bone marrow failure or leukemia.
Reasons for abnormal levels: infection, inflammation, medications, bone marrow disorders, immune disease.
Biological meaning: high counts indicate immune activation or marrow overproduction; low counts indicate reduced immune capacity or marrow suppression.
Lifestyle/family: smoking, stress, pregnancy, certain medications; family history of bone marrow disorders or congenital neutropenia increases need for testing.

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Understanding Test Results

Values above 11,000 cells/µL (leukocytosis) suggest infection, acute inflammation, stress response, corticosteroid effect, smoking, or less commonly a hematologic malignancy.
Mild elevations (11,000–15,000) often reflect mild infection or stress; moderate elevations (15,000–30,000) commonly indicate significant bacterial infection, systemic inflammation, or a leukemoid reaction; very high counts (>50,000–100,000) raise concern for leukemia or severe marrow-driven processes.
Values below 4,000 cells/µL (leukopenia) indicate reduced immune cells from viral infection, bone marrow suppression (chemotherapy, aplastic anemia), autoimmune destruction, or certain drugs.
Counts <1,000 cells/µL markedly increase infection risk; when neutrophils are specifically low (ANC <1,500 and especially <500 cells/µL) there is a high risk of serious or opportunistic infections and urgent evaluation is required.
Interpretation should consider differential (neutrophils vs lymphocytes), clinical context and repeat testing or further bone marrow and infection work-up when abnormal.

Normal Range

4,000-11,000 cells/µL OR 4.0-11.0 x10^9/L

FAQs

Q: What happens if total leucocyte count is high?

A: What happens if total leucocyte count is high? A raised white blood cell count (leucocytosis) usually signals infection, inflammation, physical stress, allergic reaction, certain drugs, or less commonly blood disorders such as leukemia. It means the immune system is activated; symptoms reflect the underlying cause. Doctors order a differential, infection tests and sometimes bone‑marrow studies to find the cause and guide treatment.

Q: What if total leucocyte count is low?

A: If total leukocyte count is low (leukopenia), you have increased infection risk. Causes include viral illness, bone‑marrow problems, autoimmune disease, certain drugs (chemotherapy, immunosuppressants) and nutrient deficiencies. Assessment: repeat CBC with differential, peripheral smear, infection/autoimmune tests, sometimes bone‑marrow exam. Treatment addresses the cause—stop offending drugs, treat infections, or use growth factors. Seek urgent care for fever.

Q: What is the danger range of TLC?

A: Total leukocyte count (TLC) normally runs about 4,000–11,000 cells/µL. Danger ranges: leukopenia below 4,000 especially <1,000 (or <500) greatly increases severe infection risk; leukocytosis above 11,000 indicates serious infection/inflammation. Extremely high counts (~30,000–50,000 cells/µL or more), called hyperleukocytosis, can cause complications and require urgent medical evaluation.

Q: What are leukocytes in pregnancy?

A: Leukocytes are white blood cells that help protect mother and fetus by fighting infection and modulating immune tolerance during pregnancy. Pregnancy normally raises leukocyte counts—especially neutrophils—leading to physiological leukocytosis. Elevated levels can be a normal adaptation, particularly in labor, but large or sudden increases may indicate infection or inflammation and should be evaluated by a healthcare provider.

Q: When to worry about high leukocytes?

A: When to worry about high leukocytes: a white blood cell count above roughly 11,000/µL is considered leukocytosis. Seek prompt medical attention if counts are very high (especially >30,000), if high counts persist on repeat tests, or if accompanied by fever, severe shortness of breath, bleeding, persistent fatigue, unexplained weight loss, night sweats, swollen lymph nodes, or abnormal blood film (immature/blast cells).

Q: What disease causes high leukocytes?

A: An elevated leukocyte (white blood cell) count—leukocytosis—most commonly reflects infection (bacterial, viral, parasitic) or inflammation. Other causes include stress, corticosteroid use, smoking, pregnancy, tissue injury/necrosis, and splenectomy. Markedly high or persistent leukocytosis can indicate hematologic malignancies such as leukemia or myeloproliferative disorders and warrants prompt evaluation with blood tests and specialist referral.