Red Blood Cell (RBC) Count

By Amber J. Tresca, About.com Guide

Updated October 26, 2012

About.com Health's Disease and Condition content is reviewed by the Medical Review Board

A blood test can provide useful information about your health.

Photo © Wojciech Wolak

See More About

What A Red Blood Cell (RBC) Count Is:

A red blood cell (RBC) count is a useful blood test that can provide information about how many red blood cells are in a person's blood. This test might be done as one component of a complete blood cell (CBC) count. A RBC count is the number of red blood cells per volume of blood, and is reported in either millions in a microliter or millions in a liter of blood.

What A RBC Count Is Used For:

Levels of RBCs out of the normal range (either higher or lower) can be an indication of certain conditions. Polycythemia is the presence of an elevated RBC count; anemia is a decreased RBC count.

Polycythemia may be caused by several conditions including congenital heart disease, cor pulmonale, dehydration (such as from severe diarrhea), obstructive lung disease, pulmonary fibrosis, or excess RBC production (polycythemia vera). Anemia may occur as a result of bleeding (including internal), hemolysis, kidney disease, leukemia, multiple myeloma, bone marrow failure, erythropoietin deficiency, or deficiencies in iron, folate, vitamin B12, or vitamin B6.

How A RBC Count Is Done:

A blood sample will be taken, normally from the arm. If several tests are ordered, more than one vial of blood will be taken. If your RBC count has been low in the past, taking blood might seem counterproductive, but the CBC count can be a very useful tool to your physician in diagnosing and treating many health conditions.