Red Blood Cell Count: The Test

How is it used?
When is it ordered?
What does the test result mean?
Is there anything else I should know?

How is it used?

A RBC count is used to evaluate any type of decrease or increase in the number of red blood cells as measured per liter of blood. These changes must be interpreted in conjunction with other parameters, such as hemoglobin, hematocrit, and/or red blood cell indicies.

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When is it ordered?

A RBC count is ordered as a part of the complete blood count (CBC), often as part of a routine physical, pre-surgical procedure, or for other clinical reasons. The test is also repeated in patients who have hematologic disorders, bleeding problems, chronic anemias, polycythemia, and/or patients undergoing chemotherapy or radiation therapy.

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What does the test result mean?
NOTE: A standard reference range is not available for this test. Because reference values are dependent on many factors, including patient age, gender, sample population, and test method, numeric test results have different meanings in different labs. Your lab report should include the specific reference range for your test. Lab Tests Online strongly recommends that you discuss your test results with your doctor. For more information on reference ranges, please read Reference Ranges and What They Mean.

A decreased number of RBCs results from either acute or chronic blood loss. Acute blood loss is a rapid depletion of blood volume. Chronic blood loss stems from various conditions that often results in some form of an anemia. Chronic anemias are due to loss of small amounts of blood over a long period of time (bleeding), mechanical destruction of the RBCs, or some physiologic problem such as decreased RBC production. Increased number of RBCs can result from a number of conditions that include dehydration, congenital heart disease, pulmonary diseases, and situations involving tissue hypoxia.

The list below includes some of these conditions.

Decreased RBC

Trauma

Burns

Pregnancy

Hemolytic anemia

Hemorrhagic infections

Gastrointestinal (GI) or other vascular bleed

Iron deficiency anemia

Vitamin B12 or folate deficiency

bone marrow damage

Metabolic disorders

Chronic inflammation

Increased RBC

Dehydration

Pulmonary disease

Congenital heart disease

Polycythemia vera

Renal problems

Over-transfusion of whole blood

Tissue hypoxia

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Is there anything else I should know?

Alteration of the number of RBCs is often transient and can be easily corrected and/or return to normal levels by eliminating the causative agent. Decreases in red blood cells are normally seen during pregnancy as a result of body fluid increases that dilute them.

Living at high altitudes causes an increase in RBC counts; this is your body's response to the decreased oxygen available at these heights.

Drugs that may increase RBC levels include gentamicin and methyldopa.

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