Erythrocyte count; Red blood cell count; Anemia - RBC count An RBC count is a blood test that measures how many red blood cells (RBCs) you have. RBCs contain hemoglobin, a protein which carries oxygen. How much oxygen your body tissues get depends on how many RBCs you have and how well they work. Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
 Blood transports oxygen and nutrients to body tissues and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For example, blood transports hormones from endocrine organs to their target organs and tissues. Blood helps maintain body temperature and normal pH levels in body tissues. The protective functions of blood include clot formation and the prevention of infection.
Routine lab tests are recommended before beginning treatment of high blood pressure to determine organ or tissue damage or other risk factors. These lab tests include urinalysis, blood cell count, blood chemistry (potassium, sodium, creatinine, fasting glucose, total cholesterol and HDL cholesterol), and an ECG (electrocardiogram). Additional tests may be recommended based on your condition. How the Test is PerformedA blood sample is needed. How to Prepare for the TestNo special preparation is necessary. How the Test will FeelWhen the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away. Why the Test is PerformedThe RBC count is almost always part of a complete blood count (CBC) test. The test can help diagnose different kinds of anemia (low number of RBCs) and other conditions affecting red blood cells. Other conditions that may require an RBC count are:
Normal ResultsNormal RBC ranges are:
The ranges above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your health care provider about the meaning of your specific test results. What Abnormal Results MeanHigher than normal numbers of RBCs may be due to:
Your RBC count will increase for several weeks when you are in a higher altitude. Drugs that can increase the RBC count include:
Lower-than-normal numbers of RBCs may be due to:
Drugs that can decrease the RBC count include:
RisksThere is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others. Other risks associated with having blood drawn are slight, but may include:
ReferencesGallagher PG. Hemolytic anemias: red blood cell membrane and metabolic defects. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 152. Little M. Anaemia. In: Cameron P, Little M, Mitra B, Deasy C, eds. Textbook of Adult Emergency Medicine. 5th ed. Philadelphia, PA: Elsevier; 2020:chap 13. Pincus MR, Abraham NZ, Bluth M. Interpreting laboratory results. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 9. Means RT. Approach to the anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 149. Version InfoLast reviewed on: 1/9/2022 Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. What causes your red blood count to go high?Your body may increase red blood cell production to compensate for any condition that results in low oxygen levels, including: Heart disease (such as congenital heart disease in adults) Heart failure. A condition present at birth that reduces the oxygen-carrying capacity of red blood cells (hemoglobinopathy)
What happens when red blood cell count is too high?Elevated red blood cells could mean that you have another, underlying health condition. Red blood cells play a big role in carrying life-giving oxygen throughout your body. But when your body makes too many, it can cause your blood to thicken and slow, making you more vulnerable to blood clots.
How do you treat high red blood cell count?If you have erythrocytosis, you may need a regular phlebotomy. This removes a small amount of blood from your body in order to lower your RBC count. If phlebotomies don't work, your doctor may prescribe hydroxyurea (Hydrea or Droxia) to reduce your RBC count.
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