Red Blood Cell (RBC) Count
Reviewed
Also called: Erythrocyte count, Red count
An RBC count measures the number of red blood cells in your blood. It is almost always part of a complete blood count (CBC) and helps diagnose red blood cell disorders such as anemia.
Specimen: Blood (from a vein in your arm)
Why this test may be ordered
- As part of a routine checkup (CBC)
- To monitor treatment that may affect blood cell counts (e.g., chemotherapy)
- To monitor health conditions such as chronic kidney disease
- If you have symptoms of a low or high red blood cell count
Preparation and collection
No special preparations needed.
A health care professional will take a blood sample from a vein in your arm using a small needle. The procedure usually takes less than five minutes.
There is very little risk to having a blood test. There may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Your results will show whether you have a normal red blood cell count or a count that is too low or too high. Your provider will consider your symptoms, medical history, and the results of other blood tests to understand your results.
- Normal RBC count: Your red blood cell count is within the expected range. Limitation: A normal result does not rule out all conditions. Your provider will interpret this result in the context of your overall health. Next step: Routine
- Low RBC count: May be a sign of anemia, leukemia, malnutrition, multiple myeloma, kidney failure, blood loss, alcohol use disorder, or pregnancy. Limitation: This result alone does not diagnose a specific condition. Further testing is needed. Next step: Prompt
- High RBC count: May be a sign of dehydration, heart disease, polycythemia vera, lung scarring, lung disease, kidney cancer, sleep apnea, or misuse of certain drugs. Living at a high altitude can also cause a high count. Limitation: This result alone does not diagnose a specific condition. Further testing is needed. Next step: Prompt
- The RBC count is often the first sign of an illness, but it is not diagnostic by itself.
- Your provider will consider your symptoms, medical history, and other test results to interpret your RBC count.
What to do next
If your results were low or high, you may need more tests such as a reticulocyte count, iron tests, or vitamin B tests to help your provider make a diagnosis. Talk to your health care provider if you have questions about your results.
- What do my RBC count results mean in my specific situation?
- Do I need any follow-up tests based on my RBC count?
- What symptoms should I watch for?
Evidence source
U.S. National Library of Medicine: Red Blood Cell (RBC) Count