White Blood Cell (WBC) Count Test: What It Measures and What Your Results Mean
This test measures the percentages of three types of white blood cells (basophils, eosinophils, and monocytes) in your blood to help evaluate your immune system and detect various health conditions.
{"Measures basophils, eosinophils, and monocytes as part of white blood cell count","Helps diagnose allergies, parasitic infections, and inflammatory conditions","Results are expressed as percentages of total white blood cells","Abnormal results may require further testing to determine the cause"}
Key facts at a glance
- LOINC
- 32350-1
- Short code
- BAS-EOS-MONO
- Synonyms
- Baso+Eos+Monos NFr Bld
- Category
- chemistry
- Sample
- whole-blood
- Container
- EDTA (K2 or K3) lavender-top vacutainer tube; alternatively EDTA microtainer for pediatric or capillary collections
- Units
- N/A
- Ref low
- 4
- Ref high
- 15
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Automated flow cytometry with impedance (CBC-Differential) and microscopic review if indicated
- CPT
- 85025
- SNOMED
- 442376000
- Specimen volume
- 3-5 mL whole blood (adult); 1-2 mL (pediatric)
- Stability
- Stable for 4-6 hours at room temperature (20-25°C) for accurate differential; up to 24 hours at 2-8°C; however, cell morphology is best preserved if analyzed within 2 hours of collection
- Hemolysis max
- 100
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 1–4 hours
- Order
- routine
This test measures the number of white blood cells, also called WBCs or leukocytes, in a sample of your blood. Because white blood cells are a key part of your immune system, this test helps your doctor check for infections, inflammation, allergic reactions, immune system disorders, or problems with your bone marrow and blood.
The Basophils, Eosinophils, and Monocytes test is part of a complete blood count (CBC) with differential. It measures the percentage of three specific types of white blood cells (leukocytes) in your blood: basophils, eosinophils, and monocytes. White blood cells are essential for your immune system and help your body fight infections and diseases.
White blood cells protect your body from illness by finding and fighting bacteria, viruses, fungi, and other harmful invaders. They also help clean up damaged cells, support tissue healing, and remember past infections so your body can respond faster in the future. Different types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each have their own specific job in keeping your immune defenses strong.
Basophils are the least common white blood cells and play a role in allergic reactions and inflammation. Eosinophils help fight parasitic infections and are involved in allergic responses. Monocytes are the largest white blood cells and help engulf and destroy germs, dead cells, and other debris in the body.
The test is performed with a simple blood draw. A healthcare professional will clean your skin, usually on the inside of your elbow, place a band around your upper arm, and collect a small sample of blood into a tube. The sample is sent to a laboratory for analysis, the procedure takes only a few minutes, and you may feel a brief sting when the needle goes in.
A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then analyzed in a laboratory using automated blood analyzers to determine the percentages of each cell type. The results are typically reported as a percentage of the total white blood cell count.
Reference range
Combined granulocyte and monocyte fraction (Basophils + Eosinophils + Monocytes): approximately 4-15% of total leukocytes; absolute count 0.2-1.5 x 10^9/L. Individual reference ranges: Basophils 0-1% (0-0.1 x 10^9/L), Eosinophils 0-5% (0-0.5 x 10^9/L), Monocytes 2-8% (0.2-0.8 x 10^9/L). Pediatric ranges vary by age.N/A
No fasting required. Patient should be well-hydrated. Avoid strenuous exercise immediately prior to collection, as it can transiently alter leukocyte counts. Inform the laboratory of any recent corticosteroid or immunosuppressive medication use.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test helps healthcare providers evaluate your immune system function. Elevated eosinophils may indicate allergic reactions, parasitic infections, or certain skin conditions. High monocyte counts may suggest chronic infections, autoimmune disorders, or certain blood cancers. Elevated basophils can be seen in allergic reactions, chronic inflammation, or certain leukemias. Low counts of these cells may result from bone marrow disorders, chemotherapy, or autoimmune conditions. This test is often used alongside other blood tests to help diagnose and monitor various medical conditions.
Frequently asked questions
Do I need to fast before this test?
Is this test painful?
What do abnormal results mean?
Will I need additional tests?
Sources
- 1
- 2
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 15, 2026. · Read our editorial policy