What is being tested?
The white blood cell (WBC) count indicates the number of white blood cells in a sample of blood. This count provides a clue to the presence of illness. White blood cells are made in the bone marrow and protect the body against infection and aid in the immune response. If an infection develops, white blood cells attack and destroy the bacteria causing the infection.

How is the sample collected for testing?
The blood sample is obtained by a needle placed in a vein in the arm or by a fingerprick or heelprick (for newborns).