Red Blood Cell Count
Does this test have other names?
RBC count, erythrocyte count
What is this test?
This test measures the number of red blood cells, or erythrocytes, in your blood.
Red blood cells play a critical role in moving oxygen from your lungs to the rest
of your body and returning carbon dioxide to your lungs to be exhaled.
A red blood cell count is typically done as part of a complete blood count (CBC).
This is a screening test to check for a variety of medical conditions.
Why do I need this test?
You may have this test if you have symptoms such as weakness or tiredness during a
general checkup. You may also have this test to look for specific health problems,
such as internal bleeding, anemia, kidney disease, and certain cancers. You may also
need this test if your healthcare provider wants to watch any of these health problems.
What other tests might I have along with this test?
A red blood cell count is often part of a complete blood count. This means that other
components of your blood, such as white blood cells and platelets, are also measured.
If your healthcare provider suspects you have a particular illness, he or she may
also order other tests needed for making a diagnosis.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
An RBC count is measured in millions per cubic millimeter (million/mm3). Normal values
may vary slightly among different laboratories. One example of normal values is:
Your healthcare provider can supply normal reference values.
An RBC that's lower than normal can be a sign of many health problems, including:
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
Your RBC count could be affected by:
How do I get ready for this test?
Your healthcare provider may suggest that you avoid:
Taking certain medicines
Be sure your provider knows about all medicines, herbs, vitamins, and supplements
you are taking. This includes medicines that don't need a prescription and any illicit
drugs you may use.