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Complete Blood Count (CBC) with Differential

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

This test measures the types and counts of cells in your blood, including red blood cells, white blood cells, and platelets, along with the proportions of different white blood cell types.

Quick summary

["A CBC helps diagnose and monitor conditions affecting your blood and immune system."]

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

Key facts at a glance

LOINC
46997-3
Short code
Num HLA Ab cells tested
Synonyms
Num HLA Ab cells tested
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Cells Are Tested?

Your blood sample is analyzed to count and identify several key components: - Red blood cells (RBCs) for oxygen transport. - White blood cells (WBCs), broken down into subtypes like neutrophils, lymphocytes, monocytes, eosinophils, and basophils, which fight infections and inflammation. - Platelets, which help with blood clotting. These results help determine if your blood is functioning normally or if there’s an imbalance that could signal illness.

Why Is This Test Done?

A CBC is commonly ordered to: - Check for infections, anemia, or bleeding disorders. - Monitor chronic conditions like cancer, leukemia, or autoimmune diseases. - Evaluate symptoms such as fatigue, fever, easy bruising, or frequent infections.

How Is the Test Performed?

A small blood sample is taken from your arm, usually by a needle. The blood is then examined under a microscope or processed through an automated machine to count and classify cells.

What Do My Results Mean?

Results may show: - Low or high counts of specific cell types, which could indicate infections, genetic disorders, or other health issues. - Abnormal cell shapes or sizes, which may point to conditions like leukemia or other blood disorders. Always discuss your results with your healthcare provider for personalized interpretation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CBC with Differential

Frequently asked questions

How often should I get a CBC test if I have no symptoms?
If you have no symptoms, a CBC might be part of routine check-ups, especially if you have risk factors like a weakened immune system, chronic illness, or a history of blood disorders. Your doctor will determine the frequency based on your health needs.
What happens if my white blood cell count is low?
A low white blood cell count (leukopenia) may mean your body has trouble fighting infections. Causes can include infections, certain medications, or underlying conditions like autoimmune diseases. Your doctor may recommend further tests or treatments to address the underlying cause.
Can diet affect my CBC results?
Yes, diet can influence blood cell counts. For example, iron deficiency can lower red blood cell counts, while certain vitamins (like B12 or folate) are important for healthy blood production. Maintaining a balanced diet and avoiding extreme dietary restrictions may help support normal blood health.
  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