The health care provider will take blood from your vein. The blood collects into an airtight container.
In infants or a young child, blood will be taken from a heel stick or finger stick. The blood is collected in a small glass tube or onto a slide or test strip.
Cotton or a bandage may be applied to stop any bleeding.
A laboratory specialist takes a drop of blood from your sample and smears it onto a glass slide. The smear is stained with a special dye, which helps tell the difference between various types of white blood cells.
Five types of white blood cells, also called leukocytes, normally appear in the blood:
- Lymphocytes (B cells and T cells)
A specially designed machine or the health care provider counts the number of each type of cell. The test shows if the number of cells are in proper proportion with one another, and if there is more or less of one cell type.