Unit Converter
White Blood Cells (WBC)
(Key Marker of Immune Status, Infection, Inflammation & Hematologic Diseases)
Synonyms
- WBC count
- Total leukocyte count (TLC)
- Leukocytes
- White cells
- Total WBC
- Peripheral white cell count
Units of Measurement
The following units represent absolute number of cells:
- 10⁹/L
- G/L (giga per liter)
- Gpt/L
- cells/L
- 10³/µL
- 1000/µL
- 10³/mm³
- 1000/mm³
- K/µL
- K/mm³
- cells/µL
- cells/mm³
All units express the same thing: total number of WBC per volume of blood.
Unit Conversions
Base equivalences
1 109/L=1 G/L=1 Gpt/L1\ \text{10}^9/\text{L} = 1\ \text{G/L} = 1\ \text{Gpt/L}1 109/L=1 G/L=1 Gpt/L 1 109/L=1000 cells/µL1\ \text{10}^9/\text{L} = 1000\ \text{cells/µL}1 109/L=1000 cells/µL 1 cells/µL=106 cells/L1\ \text{cells/µL} = 10^6\ \text{cells/L}1 cells/µL=106 cells/L 1 109/L=103/µL=1 K/µL1\ \text{10}^9/L = 10^3/\text{µL} = 1\ \text{K/µL}1 109/L=103/µL=1 K/µL
Quick conversion table
| Common Unit | Equivalent |
| 1 × 10⁹/L | 1 × 10³/µL |
| 1 × 10³/µL | 1 × 10⁹/L |
| 1 K/µL | 1 × 10³/µL |
| 1 × 10³/mm³ | 1 × 10³/µL |
| 1 G/L | 1 × 10⁹/L |
Description
White Blood Cells (WBCs) are a group of immune cells produced primarily in the bone marrow, circulating in blood to defend the body against:
- Infections (bacterial, viral, fungal, parasitic)
- Inflammation
- Allergic reactions
- Tissue injury
- Hematologic malignancies
WBC count reflects the total number of all leukocytes:
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils
A WBC count must always be interpreted with the Differential Count, clinical scenario, and other CBC parameters.
Physiological Role
White cells perform:
- Pathogen killing (phagocytosis; neutrophils & monocytes)
- Antibody production (lymphocytes)
- Immune regulation
- Allergic response (eosinophils, basophils)
- Surveillance for malignant cells
Clinical Significance
HIGH WBC COUNT
Common causes:
1. Infections
- Bacterial (most common: neutrophilia)
- Viral (lymphocytosis)
- Parasitic
- Fungal
2. Inflammation
- Rheumatoid arthritis
- IBD
- Autoimmune diseases
3. Physiological causes
- Exercise
- Pregnancy
- Stress, surgery
- Smoking
4. Medications
- Steroids
- Lithium
5. Hematologic Disorders
- Leukemia
- Myeloproliferative neoplasms
- Polycythemia vera
LOW WBC COUNT
Causes:
1. Viral infections
(Early viral suppression of bone marrow)
2. Bone marrow suppression
- Aplastic anemia
- Myelodysplastic syndromes
- Chemotherapy
- Radiotherapy
3. Autoimmune destruction
- Lupus
- Graves’ disease
4. Drug-induced
- Antithyroid drugs (carbimazole, methimazole)
- Clozapine
- Anticonvulsants
- Antibiotics (chloramphenicol)
5. Nutritional deficiencies
- Vitamin B12 deficiency
- Folate deficiency
6. Severe bacterial sepsis
(Consumption/exhaustion of WBCs)
Low WBC significantly increases risk of infection.
Reference Intervals
(Tietz 8E + CLSI + Mayo + ARUP)
Total WBC Count
- Adult: 4.0 – 11.0 × 10⁹/L
- Children: wider range (5.0 – 15.0 × 10⁹/L depending on age)
- Newborn: 9.0 – 30.0 × 10⁹/L
Leukopenia
- < 4.0 × 10⁹/L
Leukocytosis
- > 11.0 × 10⁹/L
All units measure the same parameter using different volume scales.
Diagnostic Uses
1. Infection Assessment
Most common use.
2. Hematologic Malignancy Screening
Leukemia/myeloproliferative disorders.
3. Immune Status Evaluation
Lymphopenia = immunodeficiency.
4. Monitoring of Chemotherapy
Predicts risk of neutropenic sepsis.
5. Autoimmune Disease Activity
E.g., SLE often causes leukopenia.
6. Inflammatory Disorders
High WBC reflects ongoing inflammation.
Analytical Notes
- Automated analyzers provide total & differential.
- Manual counts (hemocytometer) rarely used but confirm abnormal results.
- Hemolysis has minimal effect.
- Clotted samples give falsely low WBC (platelet clumping on analyzer flags).
- Dilution or instrument error occurs in extremely high counts (>100 ×10⁹/L).
Clinical Pearls
- Always interpret WBC with Differential (neutrophils, lymphocytes).
- Stress response can cause transient WBC ↑.
- Steroids consistently increase WBC via demargination.
- In B12 deficiency, pancytopenia may occur with low WBC.
- Leukemoid reaction (WBC >50 ×10⁹/L) must be differentiated from leukemia.
- ANC (Absolute Neutrophil Count) is more clinically relevant in neutropenia.
Interesting Fact
During acute stress, ~50% of neutrophils shift from vessel walls (“marginated pool”) into circulation - causing a rapid increase in WBC count without any new cell production.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Hematology
- CLSI Hematology Standards (H20, H26)
- British Society for Haematology (BSH) - Leukocyte Guidelines
- Mayo Clinic Laboratories - WBC Count
- ARUP Consult - CBC Interpretation
- NIH / MedlinePlus - WBC Test