White Blood Cell Count with Differential (Serum/Plasma or Whole Blood): This test gives you and your doctor a detailed look at the white blood cells in your sample.

What This Test Measures: This section explains that the test counts the five main types of white blood cells and shows their percentages so you can understand your immune status.

A white blood cell differential (also called a WBC differential) breaks down the five main types of white blood cells into their individual counts. These include neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each type plays a unique role in your immune response and helps your body fight different threats.

Why It’s Done: Your doctor may recommend this test to look for causes of illness, to check your immune system, or to monitor a known condition over time.

Doctors may order this test to diagnose infections (like bacterial or viral), autoimmune diseases, allergies, or conditions affecting your bone marrow. It can also help monitor treatment progress for blood disorders or cancer and guide adjustments in your care.

Sample Collection and Preparation: This part describes how your blood sample is taken from a vein and prepared in the lab so the white blood cells can be correctly counted and identified.

Blood is drawn from a vein, typically in your arm. The sample is sent to a lab where it’s analyzed under a microscope to count and identify each type of white blood cell. Sometimes, a blood smear is prepared for closer examination by a specialist.

Common Reasons for Testing: People often have this test when they have ongoing symptoms such as fever, tiredness, or infections that need further investigation by their healthcare provider.

Frequent reasons include unexplained fevers, chronic infections, fatigue, or symptoms like swollen lymph nodes. It may also be used to check for conditions like leukemia, lymphoma, or immune deficiencies that affect your blood and immunity.