Red Blood Cell (RBC) Count Test
A red blood cell (RBC) count measures the number of red blood cells in your blood. These cells carry oxygen from your lungs to every cell in your body. An abnormal count can be an early sign of illness.
What this test measures
A red blood cell (RBC) count measures the number of red blood cells, also known as erythrocytes, in your blood. Red blood cells are made in your bone marrow and contain hemoglobin, an iron-rich protein that carries oxygen from your lungs to every cell in your body.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
Conditions that may cause a high red blood cell count include dehydration, heart disease, polycythemia vera, scarring of the lungs (often due to cigarette smoking), lung disease, kidney cancer, sleep apnea, misuse of certain drugs for athletic performance (such as anabolic steroids), and living at a high altitude.
Lower-than-normal results
Conditions that may cause a low red blood cell count include anemia, leukemia, malnutrition, multiple myeloma, kidney failure, blood loss from injury or other problems, alcohol use disorder, and pregnancy.
Frequently asked questions
What is a red blood cell (RBC) count?
It measures the number of red blood cells in your blood. Red blood cells carry oxygen from your lungs to every cell in your body.
Why is an RBC count done?
It is almost always part of a complete blood count (CBC) and helps diagnose red blood cell disorders such as anemia.
What does a low RBC count mean?
A low RBC count can be caused by anemia, leukemia, malnutrition, multiple myeloma, kidney failure, blood loss, alcohol use disorder, or pregnancy.
What does a high RBC count mean?
A high RBC count can be caused by dehydration, heart disease, polycythemia vera, lung scarring, lung disease, kidney cancer, sleep apnea, misuse of certain drugs, or living at high altitude.
How should I interpret my RBC count results?
Talk to your health care provider. They will consider your symptoms, medical history, and other blood test results to understand your RBC count.
Related lab tests
Sources
- MedlinePlus: Red Blood Cell (RBC) Count — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.