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Red Blood Cell Count (with Differential Count)

Published: August 9, 2026Updated: August 16, 2026

This test measures the number of different types of white blood cells and red blood cells in your blood. It helps assess your immune system and overall blood health.

Quick summary

["Understanding your blood cell composition can help detect infections, anemia, or other conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
17124-9
Short code
CD2CD20
Synonyms
CD2+CD20+ Cells NFr Bld
Category
chemistry
Sample
whole-blood
Container
EDTA (lavender/purple-top) anticoagulant tube; alternatively, sodium heparin (green-top) tube for flow cytometry applications
Units
N/A
Ref low
0
Ref high
1
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Flow cytometry (multiparametric immunophenotyping using fluorescently labeled monoclonal antibodies against CD2 and CD20 surface markers)
CPT
86356 (Monoclonal antibody, flow cytometry, each additional marker); commonly reported with 86355 for the primary marker
SNOMED
395124008
Specimen volume
3-5 mL of whole blood; minimum 1 mL for pediatric samples
Stability
Specimen should be processed within 24-48 hours of collection when stored at room temperature (18-25°C). Do not refrigerate, as cold exposure may affect cell viability and surface marker expression.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
24–72 hours
Order
routine

Why This Test Is Done

Doctors may order this test to diagnose or monitor conditions like infections, blood disorders, or immune system issues. It’s also used during pregnancy to check for anemia or other blood-related problems.

What to Expect Before the Test

No special preparation is needed. You’ll typically have a small needle inserted into your arm or hand to draw a blood sample. If you’re nervous, let your doctor or phlebotomist know—many people find it less painful than they expect.

What the Results Mean

The test provides a breakdown of your red blood cells (RBCs), white blood cells (WBCs), and sometimes platelets. Each type of white blood cell (neutrophils, lymphocytes, etc.) has a role in your body’s defense. Abnormal counts may signal infections, allergies, or other health concerns.

Common Conditions Linked to Abnormal Results

High or low counts of certain white blood cells can indicate infections, autoimmune diseases, or chronic illnesses. For example, high neutrophil counts might suggest bacterial infections, while low lymphocyte counts could point to weakened immunity.

Reference range

CD2+CD20+ dual-positive lymphocytes are typically rare or absent in healthy peripheral blood (<1% of total lymphocytes). CD2 is a pan-T-cell marker and CD20 is a B-cell marker; co-expression is unusual in normal immunophenotyping. Reference ranges should be established by individual laboratories based on their instrumentation and patient population.N/A

Specimen: whole-blood

No special patient preparation is typically required. However, patients should be well-hydrated. Information regarding recent corticosteroid therapy, chemotherapy, or immunosuppressive medications should be provided, as these may affect lymphocyte subset counts.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

RBC Differential (Blood Cell Count)

Frequently asked questions

What does a ‘differential count’ measure exactly?
A differential count identifies the percentage of each type of white blood cell (e.g., neutrophils, lymphocytes, eosinophils) in your blood sample. It’s not a single number but a breakdown that helps pinpoint specific health concerns.
How often should I get this test?
Your doctor will determine how often you need this test based on your health status, symptoms, or ongoing treatments. Regular checks may be recommended if you have chronic conditions like cancer or autoimmune diseases.
Can diet affect my blood cell counts?
Yes, diet can influence blood cell counts. For example, iron-rich foods may help prevent anemia, while certain vitamins (like B12 or folate) support red blood cell production. However, diet alone won’t replace a blood test—it’s best to discuss dietary habits with your doctor.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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