Red Blood Cell Count Test (RBC) – Why am I having this test?

Red blood cell count test is done to see how many RBCs you have. RBCs are made in your bone marrow. They circulate in your bloodstream for about 120 days, until they are destroyed by your spleen. These cells are important because they contain hemoglobin, which carries oxygen to body tissues. Having an abnormally low number of RBCs causes anemia.

You may have this test as a part of a complete blood count (CBC) test that counts RBCs, white blood cells, and platelets. It may also be done if your health care provider suspects that you have certain medical conditions. These may include abnormally low production of red blood cells or abnormally fast destruction of red blood cells (hemolysis).

What is being tested?

This test measures the total number of circulating RBCs in a portion of your blood.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel or by sticking a finger with a small needle.

Tell a health care provider about:

• All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.
• Whether you are pregnant or may be pregnant.

How are the results reported?

Your test results will be reported as a value that indicates the number of RBCs. The International System of Units (SI units) is used to measure RBCs. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

• Adult or elderly:
  • Male: 4.7–6.1.
  • Female: 4.2–5.4.
• Children:
  • Newborn: 4.8–7.1.
  • 2–8 weeks: 4.0–6.0.
  • 2–6 months: 3.5–5.5.
  • 6 months–1 year: 3.5–5.2.
  • 1–6 years: 4.0–5.5.
  • 6–18 years: 4.0–5.5.

What do the results mean?

Results that are within the reference ranges are considered normal. Test results that are higher than the reference ranges can indicate a number of health conditions. These may include:

• Excess RBCs (erythrocytosis).
• Heart disease that is present at birth (congenital).
• Severe chronic obstructive pulmonary disease (COPD).
• A bone marrow disorder that causes overproduction of RBCs (polycythemia vera).

Test results that are lower than the reference ranges can indicate:

• Anemia.
• Disorders that result from abnormal hemoglobin (hemoglobinopathy).
• Long-term (chronic) fluid overload due to liver disease (also called cirrhosis).
• Anemia caused by hemolysis.
• Excessive bleeding (hemorrhage).
• Dietary deficiencies such as low iron or vitamin B12 intake.
• Bone marrow failure.
• Presence of an artificial (prosthetic) heart valve. Mechanical valves may damage the RBCs, causing them to decrease in number.
• Kidney disease.
• Pregnancy.
• Vascular diseases such as rheumatoid arthritis, systemic lupus erythematosus, or sarcoidosis.
• Cancers such as lymphoma, leukemia, Hodgkin’s disease, or multiple myeloma.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

• When will my results be ready?
• How will I get my results?
• What are my treatment options?
• What other tests do I need?
• What are my next steps?

Summary

• A red blood cell (RBC) count is a test to see how many RBCs you have.
• RBCs are made in your bone marrow, and they circulate in your bloodstream for about 120 days. They are important because they contain hemoglobin, which carries oxygen to your body tissues.
• A variety of health conditions can lead to low or high RBC counts.
• Talk with your health care provider about what your test results mean.