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 (RBC) count is typically done as part of a complete blood count.
This is a screening test to check for a variety of medical conditions.
Why do I need this test?
You may need 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.
Your healthcare provider may also want this test done to determine if your RBC count
is too high.
What other tests might I have along with this test?
A red blood cell count is often part of a complete blood count (CBC). This means that other
components of your blood are also measured. These include white blood cells, your
hemoglobin level, and platelets.
If your healthcare provider suspects you have a particular illness, they may also
order other tests needed for making a diagnosis.
What do my test results mean?
Test results may vary depending on your age, gender, health history, and other things.
Your test results may be different depending on the lab used. They may not mean you
have a problem. Ask your healthcare provider what your test results mean for you.
An RBC count is measured in millions per cubic millimeter (million/mm3). Normal values
may vary slightly among different labs. One example of normal values is:
Your healthcare provider can supply normal reference values.
An RBC count that's lower than normal can be a sign of many health problems, including:
An RBC count that is higher than normal can be a sign of many health problems, including:
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be 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 not:
Take certain medicines
Tell your provider about all medicines, herbs, vitamins, and supplements you are taking.
This includes medicines that don't need a prescription and any illegal drugs you may