Blood Disorders Print Understanding the Red Blood Cell (RBC) Count Medically reviewed by facebook linkedin Medically reviewed by Richard N. Fogoros, MD on September 26, 2019 Richard N. Fogoros, MD, is a retired professor of medicine and board-certified internal medicine physician and cardiologist. He is Verywell's Senior Medical Advisor. Learn about our Medical Review Board Richard N. Fogoros, MD Written by facebook twitter linkedin Written by Amber J. Tresca Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16. Learn about our editorial policy Amber J. Tresca Updated on October 21, 2019 More in Blood Disorders Anemia White Blood Cell Disorders Polycythemia Vera & Myelofibrosis CBC Test Analyzer In This Article Table of Contents Expand Overview Normal Ranges Causes of High and Low Counts Improving RBC View All Back To Top The red blood cell (RBC) count is used to measure the number of oxygen-carrying blood cells in a volume of blood. It is one of the key measures we use to determine how much oxygen is being transported to cells of the body. An abnormal RBC count is often the first sign of an illness that may either be undiagnosed or without symptoms. At other times, the test can point the doctor in the direction of a diagnosis if there are symptoms, such as shortness of breath or fatigue, which cannot be readily explained. Verywell Understanding the Complete Blood Count Typically speaking, an RBC count is less useful on its own to diagnose a medical condition. Instead, it is most often performed as part of a more comprehensive test called a complete blood cell (CBC) count which measures the composition cells in a blood sample. They include: Red blood cells (RBC) which transport oxygen to cells of the bodyWhite blood cells (WBC), which are a part of the immune systemHemoglobin (Hb), a protein which carries oxygen and carbon dioxide moleculesPlatelets (PLT), the cells responsible for blood clottingHematocrit (Hct), the ratio of RBC to the total volume of blood Based on the composition of blood cells, doctors can better know where to focus their investigation and which areas they can probably avoid. Learn What the Results of a Complete Blood Count Tell Your Doctor Normal Ranges An RBC count is the number of red blood cell per a particular volume of blood. It may be reported in millions of cells per microliter (mcL) of blood or in millions of cells per liter (L) of blood. The "normal" range can sometimes vary by population. Many reference values will be far higher in high-altitude cities like Denver and far lower in low-altitude areas like the Gulf Coast. As such, the ranges cannot be considered hard-and-fast values but rather, as the name suggests, a reference point. The "normal" RBC reference range for women is 4.2 to 5.4 million/mcL; for men, 4.7 to 6.1 million/mcL; for children, 4.0 to 5.5 million/mcL. Causes of High and Low RBC Counts A high RBC count tells us that there has been an increase in oxygen-carrying cells in blood. This usually indicates that the body is compensating for some condition that is depriving the body of oxygen, including: Congenital heart diseaseHeart failureChronic obstructive pulmonary disease (COPD)Pulmonary fibrosis, often due to smokingPolycythemia vera, a bone marrow diseasePerformance-enhancing drugs, which stimulate RBC productionRenal cell carcinoma, a type of kidney cancerDehydration A low RBC count indicates a decrease in oxygen-carrying cells in the blood. The causes can be many, ranging from infections and deficiencies to malnutrition to malignancies, including: AnemiaKidney failureThyroid problemsBleeding, internal or externalLeukemia, a type of blood cancerDrug side effects, including chemotherapyMultiple myelomas, a type of cancer affecting plasma cellsErythropoietin deficiency, a kidney hormone that promotes RBC growthDeficiencies in iron, folate, vitamin B12, or vitamin B6Hemolysis, the abnormal breakdown of red blood cellsPregnancy Inasmuch as an RBC count can help diagnose a medical condition, it's also used to monitor treatment. If you've been diagnosed with a blood disorder or are taking any medications that affect your RBC, your doctor will want to monitor this as a matter of course. This is especially true for cancer and cancer chemotherapy, both of which can have a detrimental cause-and-effect impact on blood counts. Things You Can Do to Improve Your RBC Treatment of an abnormal RBC count is typically focused on treating the underlying condition, whether it be an infection, injury, cancer, or a genetic disorder. If, on the other hand, the cause is related to a nutritional deficiency, medication use, or a chronic condition, there may be things you can do to not only improve your blood count but your overall health, as well. If you have a high RBC count: Exercise to improve heart and lung function.Eat less red meat and iron-rich foods.Avoid iron supplements.Keep yourself well hydrated.Avoid diuretics, including coffee and caffeinated drinks.Stop smoking, especially if you have COPD or pulmonary fibrosis.Avoid the use of steroids and other performance-enhancing drugs. If you have a low RBC count (including anemia): Maintain a healthy, balanced diet.Take a daily vitamin and iron supplement, if needed.Exercise regular to improve heart and lung function.Stop smoking.Avoid aspirin which can thin blood.Take your thyroid medications as prescribed if you have thyroid problems. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. George-Gay B, Parker K. Understanding the complete blood count with differential. J Perianesth Nurs. 2003;18(2):96-114. doi:10.1053/jpan.2003.50013 Leukemia & Lymphoma Society. Understanding Blood Counts. National Heart, Blood, and Lung Institute. Iron-Deficiency Anemia. Additional Reading American Association for Clinical Chemistry/Lab Tests Online. Red Blood Cell Count (RBC). Updated April 10, 2019. Bunn, H. “Chapter 158: Approach to the anemias.” In: Goldman L, Schafer AI, Eds. Goldman's Cecil Medicine (25th edition). Philadelphia: Elsevier Saunders; 2015. Goljan EF. “Chapter 12: Red blood cell disorders.: In: Goljan E, ed. Rapid Review Pathology (4th edition). Philadelphia: Elsevier Saunders; 2014. Continue Reading