CBC

Alternative names:

complete blood count

What the risks are:

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Special considerations:

Red blood cells transport hemoglobin which, in turn, transport oxygen. The amount of oxygen received by tissue depends on the amount and function of RBCs and hemoglobin. The MCV, MCH, and MCHC reflect the size and hemoglobin content of individual red blood cells.

The hematocrit is an expression of the proportion of whole blood that is composed of red blood cells (since the contribution by the WBCs is almost negligible). The hematocrit is a compound measure of RBC number and size.

White blood cells are mediators of inflammation and the immune response. There are various types of WBCs that normally appear in the blood: neutrophils (polymorphonuclear leukocytes; PMNs), band cells (slightly immature neutrophils), T-type lymphocytes (T cells), B-type lymphocytes (B cells), monocytes, eosinophils, and basophils.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.