Why Would a Doctor Order a CBC with Differential?

When you visit a doctor for a routine checkup or due to specific symptoms, you may hear them mention that they are ordering a “CBC with differential” as part of your tests. But what does this mean, and why would a doctor consider this test necessary?

What does CBC with Differential Platelet Test For?

A Complete Blood Count (CBC) with differential is an extensive blood test that examines various aspects of your blood, including:

  • Red Blood Cells (RBC): These cells transport oxygen from your lungs to other body parts.
  • White Blood Cells (WBC): These cells are crucial for fighting infections. A CBC with differential specifically counts the different types of white blood cells—Neutrophils, Lymphocytes, Monocytes, Eosinophils, and Basophils—in your blood.
  • Platelets: These are tiny blood cells that help your body form clots to stop bleeding.
  • Hemoglobin: This protein is in red blood cells that carries oxygen.
  • Hematocrit: This measures how much of your blood is comprised of red blood cells.
  • Mean Corpuscular Volume (MCV): This refrers to the average size of your red blood cells.

What Does a Differential Blood Count Tell You?

The differential blood count is like a deeper dive into your white blood cells. It measures the percentage of each type of white blood cell, which can be crucial for diagnosing various conditions, including infections, immune system disorders, and even certain types of cancer.

What is a Normal CBC with Platelet Count?

Normal results may vary between laboratories, but generally, they look like:

  • RBC Count: 4.7 to 6.1 million cells/mcL for males; 4.2 to 5.4 million cells/mcL for females
  • WBC Count: 4,500 to 10,000 cells/mcL
  • Hematocrit: 40.7% to 50.3% for males; 36.1% to 44.3% for females
  • Hemoglobin: 13.8 to 17.2 gm/dL for males; 12.1 to 15.1 gm/dL for females
  • Platelet Count: 150,000 to 450,000/dL

Do You Need to Fast for CBC with Differential Platelet Count?

Generally, fasting is not required for a CBC with differential. However, your healthcare provider will inform you if any other tests requiring fasting will be done concurrently.

What Cancers are Detected by Blood Tests?

Blood tests are particularly useful for identifying blood cancers like leukemia, Hodgkin lymphoma, non-Hodgkin lymphoma, and multiple myeloma. Certain tumor markers can also be identified, which may suggest the presence of other types of cancer.

Do All Cancers Show Up in Bloodwork?

Not all types of cancer are detectable through a CBC. For example, leukemia can often be detected through a CBC with differential, but additional tests are usually required for a confirmed diagnosis.

What are the Signs of Leukemia in Blood Work?

In cases of leukemia, a CBC with differential may reveal an abnormal level of white blood cells. Low levels of red blood cells or platelets can also be indicative. To confirm the diagnosis, further tests like a bone marrow biopsy may be required.

Would a Full Blood Count Show Anything Serious?

A full blood count can help identify a variety of conditions, from minor infections to severe illnesses, including blood disorders and certain types of cancer.

What Happens if the Differential Count is High?

If the differential count is abnormally high, it doesn’t automatically mean something serious is happening. Diet, medications, and even the menstrual cycle can affect test results. Your doctor will interpret the findings in conjunction with your overall medical history, symptoms, and other tests to arrive at an accurate diagnosis. Additional tests may be needed.

Can I Order a Complete Blood Count (CBC) with Differential and Platelets Blood Test

You can order a CBC blood test online at Walk-In Lab.  


A CBC with differential is a crucial test that provides an overview of a person’s health, helping to detect a variety of potential problems ranging from anemia to infection to cancer. If your doctor orders this test, it’s usually a proactive measure to better understand your health or diagnose a suspected condition more accurately.


  1. MedlinePlus – Complete Blood Count
  2. Mount Sinai Health System – Blood Differential Test
  3. Cleveland Clinic – Blood Tests for Cancer: Diagnosis & Treatment
  4. Cancer.Net – Understanding Your Complete Blood Count
  5. Moffitt – Can Blood Work Detect Cancer?
  6. Moffitt – Leukemia Diagnosis

By understanding the components and importance of a CBC with differential, you can engage more meaningfully with your healthcare provider about your test results and what they could mean for your health.

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