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 health care 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 health care 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 health care 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:

• 3.6 to 5 million/mm3 for females.

• 4.2 to 5.4 million/mm3 for males.

Your provider can supply normal reference values.

An RBC count that's lower than normal can be a sign of many health problems, including:

• Anemia.

• Vitamin B-12 or folate deficiency.

• Stomach ulcers.

• Bleeding.

• Lupus.

• Hodgkin lymphoma.

• Leukemia.

• Multiple myeloma.

An RBC count that is higher than normal can be a sign of many health problems, including:

• Dehydration.

• Lung diseases.

• Heart diseases.

• Kidney diseases.

• Blood disorders. 

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:

• Dehydration.

• Overhydration.

• Stress.

• Altitude.

• Pregnancy.

• Some medicines.

• Your position when the blood is drawn.

How do I get ready for this test?

Your health care provider may suggest that you not:

• Exercise heavily.

• Be stressed.

• Become dehydrated.

• Drink alcohol.

• 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 use.