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Red Blood Cell Count Test

Last updated April 2, 2020

The Red Blood Cell Count Test is a blood test to measure the number of circulating RBCs in the body.

What are other Names for this Test? (Equivalent Terms)

  • Erythrocyte Count Blood Test
  • RBC Count Test

What is Red Blood Cell Count Test? (Background Information)

  • Red blood cells (RBCs) are the principle ‘gas’ transport vehicles of the body. They supply tissues with oxygen and carry carbon dioxide away to the lungs, for excretion
  • RBCs have a maximum lifespan of 120 days; they may also frequently breakdown before this time. After outliving their usefulness, the RBCs are recycled by the liver, spleen, and the circulating white blood cells
  • New RBCs are produced in the bone marrow through a process called erythropoiesis. Bone marrow is the spongy tissue inside bones, which is responsible for producing other blood cells, as well. These include the white blood cells and megakaryocytes, which are ‘platelet precursors’
  • Erythropoiesis is subject to regulation by hormones, one of which is erythropoietin (EPO). EPO is released in response to an increased demand by tissues for oxygen. This may occur, such as, when relocating to an environment with less oxygen i.e., to higher altitudes
  • RBC count can either be abnormally increased or decreased leading to a variety of signs and symptoms:
    • An insufficient number of RBCs results in anemia. Reduced RBC numbers may be due to various causes, such as the body’s own destruction of the RBCs or bone marrow failure. Such a reduction in the RBC numbers can cause the tissues to become deprived of oxygen and accumulate carbon dioxide. This often results in fatigue and a pale skin appearance (pallor). Because the bone marrow is unable to make enough RBCs in such a scenario, there is a decrease in the red blood cell count. In normal individuals, where the bone marrow is functioning normally, a decreased oxygen to the tissue will cause the bone marrow to make more red blood cells. This is called compensatory physiological erythrocytosis
    • Increased RBC count, due to conditions such as burns, oxygen deprivation, or smoking, can cause a variety of signs and symptoms such as shortness of breath, fatigue, and joint pain. Under such conditions, the body physiologically compensates for a low oxygen environment by increasing the red blood cell count
  • The Red Blood Cell Count Test is a blood test to measure the number of circulating RBCs in the body. It can be ordered for various reasons, such as the routine screening of an individual, bone marrow disorders, blood loss due to a trauma, chemotherapy, etc.

This test is almost never performed in isolation, but as part of the complete blood count (CBC) test, which includes white blood cell (WBC) and platelet counts too.

What are the Clinical Indications for performing the Red Blood Cell Count Test?

The clinical indications for performing a Red Blood Cell Count Test may include: 

  • Routine screening, as part of a complete blood count (CBC) test
  • Signs of anemia such as easy fatigue, pale appearance of skin (pallor), shortness of breath (usually with physical activity), and dizziness
  • Presence of certain symptoms such as headaches, itchy skin, increased heart rate, joint pain, etc.
  • Acute or chronic bleeding that may be caused due to ulcers, certain malignancies, heavy menstrual bleeding, etc.
  • Any bleeding or clotting disorders
  • Certain autoimmune diseases and chronic inflammatory diseases causing anemia
  • Enlargement of the spleen (splenomegaly)
  • Difficulty adapting to altitude changes
  • Monitoring the effects or progression of:
    • Chronic blood loss such as after a trauma
    • Burns 
    • Chronic obstructive pulmonary disease (COPD)
    • Bone marrow disorders such as polycythemia vera
    • Organ failure
    • Autoimmune diseases 
    • Chemotherapy
    • Certain renal conditions

How is the Specimen Collected for Red Blood Cell Count Test?

Following is the specimen collection process for Red Blood Cell Count Test:

Sample required: Blood

Process of obtaining blood sample in adults (and children):

  • A band is wrapped around the arm, 3-4 inches above the collection site (superficial vein that lies within the elbow pit)
  • The site is cleaned with 70% alcohol in an outward spiral, away from the zone of needle insertion
  • The needle cap is removed and is held in line with the vein, pulling the skin tight
  • With a small and quick thrust, the vein is penetrated using the needle
  • The required amount of blood sample is collected by pulling the plunger of the syringe out slowly
  • The wrap band is removed, gauze is placed on the collection site, and the needle is removed
  • The blood is immediately transferred into the blood container, which has the appropriate preservative/clot activator/anti-coagulant
  • The syringe and the needle are disposed into the appropriate “sharp container” for safe and hygienic disposal

In newborns: Blood sample is drawn from the heel after making a small nick using a scalpel. This is called heel stick.

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Red Blood Cell Count Test Result?

The significance of Red Blood Cell Count Test is explained.

  • A low RBC count may be indicative of the following conditions:
    • Hemolytic anemia
    • Internal or external bleeding (hemorrhage)
    • Iron or copper deficiency
    • Hodgkin’s disease
    • Leukemia
    • Multiple myeloma
    • Vitamin B6, B12, or folic acid deficiency
    • Hemoglobinopathies such as sickle cell anemia, thalassemia, G6PD deficiency disorder, etc.
    • Other bleeding and clotting disorders
    • Kidney disease and kidney failure
    • Certain thyroid abnormalities
    • Conditions causing bone marrow failure
  • A high RBC count may be indicative of the following conditions:
    • Severe burns
    • Oxygen deprivation, such as occurring with high altitudes
    • Chronic obstructive pulmonary disease (COPD); lung fibrosis
    • Congenital heart disease
    • Dehydration
    • Polycythemia vera
    • Thalassemia
    • Sleep apnea
    • Cigarette smoking
    • Renal cell carcinoma
  • Some individuals may have physiologically low RBC count. This is called physiological anemia. Such individuals do not show any symptoms of anemia. On the other hand, some individuals have naturally increased red cells as a normal state. This is called physiological erythrocytosis; such individuals also do not show any symptoms

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • There are certain factors that interfere with the Red Blood Cell Count Test and these include:
    • Exercise and stress
    • Smoking: Cigarette smoking causes reduced oxygenated blood in the body. This stimulates the bone marrow to increase the number of RBCs
    • Genetic variations
    • High altitudes
    • Certain medications, diuretics, etc.
    • Body hydration status
    • Use of performance-enhancing drugs such as anabolic steroids and certain protein injections
  • Medications that can cause low RBC count in the body include chloramphenicol (antibiotic), hydantoin (anticonvulsant), and quinidine (an antiarrhythmic agent). Medications causing high RBC count may include gentamicin (antibiotic) and methyldopa (for treating hypertension)
  • Decreased erythropoietin production may take place due to renal disease or renal failure; whereas, the presence of certain renal tumors may vastly increase the RBC count
  • Athletes may increase the numbers of “gas-exchanging RBCs” to gain a competitive edge. This may be achieved in the body by:
    • Supplementation of erythropoietin, to stimulate erythropoiesis
    • Withdrawing RBCs from the bloodstream and re-injecting them at a later time, closer to the competition dates, a process known as blood doping
  • Blood doping is an extremely dangerous practice, because it results in a thicker and more viscous blood that is much harder for the heart to pump. This may cause severe health issues in the body requiring hospitalization; the condition can even result in death

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: April 2, 2020
Last updated: April 2, 2020