Red Blood Cell Count (RBC)
The RBC count measures how many red blood cells are in a specific volume of your blood. Red blood cells are produced in bone marrow and live about 120 days. They are responsible for carrying oxygen to tissues and removing carbon dioxide. An abnormal count often signals anemia, blood loss, or bone marrow problems.
Reference Ranges
Male
4.7 – 6.1
million/µL
Female
4.2 – 5.4
million/µL
Child
4 – 5.5
million/µL
Ages 6–12
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
A low RBC count means fewer cells are available to carry oxygen, leading to anemia symptoms — fatigue, pallor, shortness of breath. Causes include iron deficiency, B12/folate deficiency, chronic kidney disease, bone marrow failure, or blood loss.
What High Levels Mean
A high RBC count (erythrocytosis) can result from dehydration, smoking, chronic lung disease, living at high altitude, or polycythemia vera. More red cells make blood thicker, increasing clot risk.
Frequently Asked Questions
Is RBC count the same as hemoglobin?
No, but they are related. RBC count tells you how many red blood cells you have, while hemoglobin measures the oxygen-carrying protein inside those cells. You can have a normal RBC count but low hemoglobin if each cell has less hemoglobin than normal.
What causes a low RBC count?
Common causes include iron, vitamin B12, or folate deficiency; chronic kidney disease (which reduces erythropoietin); bone marrow disorders; autoimmune conditions that destroy red cells; and significant blood loss from injury or menstruation.
Can exercise affect RBC count?
Regular endurance exercise can slightly increase RBC production as the body adapts to higher oxygen demands. However, intense training can also cause temporary drops due to plasma volume expansion — a harmless phenomenon called 'sports anemia'.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
Read Full Medical Disclaimer →