White Blood Cell Differential (Manual Count)

Why This Test Is Done

Doctors may order a white blood cell differential when you have symptoms like fever, fatigue, or unexplained weight loss. It’s also used to monitor conditions such as infections, autoimmune diseases, or blood disorders. Sometimes, it’s part of routine check-ups or before treatments that could affect your immune system.

What to Expect Before the Test

No special preparation is needed for this test. A simple blood draw is performed in a clinic or lab. If you’re on certain medications (like steroids), let your provider know, as they might affect your results.

What the Test Measures

The manual differential counts five main types of white blood cells: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each type has a distinct role in fighting infections or regulating immune responses. The percentages of these cells help diagnose conditions like allergies, infections, or leukemia.

How Results Are Interpreted

Results are typically expressed as percentages of each cell type. For example, a high neutrophil count might suggest a bacterial infection, while a high lymphocyte count could indicate a viral infection or immune response. Your doctor will compare these results to your overall health and symptoms to make a diagnosis.