Peripheral Blood Smear with Differential White Blood Cell Count (WBC)
This test examines your blood sample under a microscope to count and identify different types of white blood cells (WBCs), also called leukocytes. It helps assess immune function and detect abnormalities like infections, inflammation, or blood disorders.
["A blood smear and WBC count can reveal clues about your health, especially concerning infections or immune system issues."]
Key facts at a glance
- LOINC
- 765-8
- Short code
- Neuts Hyperseg Bld Ql Smear
- Synonyms
- Neuts Hyperseg Bld Ql Smear
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 0.4
- Ref high
- 4
- Critical range
- 0.1 N/A – 20 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- microscopy-light
- CPT
- 84443
- SNOMED
- 301343003
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What Is a Differential White Blood Cell Count?
A differential white blood cell count (diff) breaks down the total WBC count into five main types: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each type serves a unique role in fighting infections or responding to inflammation.
Why Might You Need This Test?
Your doctor may order this test to diagnose or monitor conditions like infections (e.g., bacterial, viral), autoimmune diseases, blood cancers, or allergic reactions. It’s also useful before surgeries or treatments that affect the immune system.
How Is the Test Performed?
A small blood sample is drawn from a vein, typically in your arm. The blood is spread thinly on a microscope slide and stained to highlight different cell types. A trained lab technician then examines the slide under a microscope to count and classify each WBC type.
What Does the Test Tell You?
The results show the percentage of each WBC type relative to the total WBC count. For example, an elevated neutrophil count might suggest an infection, while a high lymphocyte count could indicate chronic illness or immune response.
Reference range
Adult: 0.4-4.0 mIU/LN/A
Take your thyroid medication after the blood draw if applicable. No fasting required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
WBC smear & diff
Frequently asked questions
How long will it take to get my results?
Can I eat or drink before this test?
What are the risks or side effects of this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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 16, 2026. · Read our editorial policy