White Blood Cell Count with Differential (Serum/Plasma or Whole Blood)

Why This Test Is Done

Doctors may order this test to evaluate immune system function, detect infections (like bacterial or viral), check for blood disorders (such as leukemia or anemia), or monitor conditions like autoimmune diseases or chronic inflammation. It can also be used during pregnancy to screen for certain risks or after treatments like chemotherapy.

What to Expect Before the Test

No special preparation is needed for this test. You may donate blood or have a small sample drawn from your vein. If you’re taking certain medications (like steroids), let your healthcare provider know, as they might affect your results.

What Happens During the Test

A healthcare professional will insert a needle into your arm to draw blood. The sample is then sent to a lab, where it’s analyzed to count and identify the different types of white blood cells (neutrophils, lymphocytes, monocytes, eosinophils, and basophils).

What the Results Mean

Your results will show the absolute counts of each WBC type. Abnormal levels can signal conditions like low immunity (e.g., low lymphocytes), infections (e.g., high neutrophils), or allergic reactions (e.g., high eosinophils). Your doctor will interpret these findings in the context of your overall health and symptoms.