Normal, High, and Low RBC Count

Red Blood Cells Count is a count of the number of circulating RBCs in 1 mm3 of peripheral venous blood. The RBC count is routinely performed as part of a complete blood cell count. Within each RBC are molecules of hemoglobin that permit the transport and exchange of oxygen to the tissues and carbon dioxide from the tissues. The RBC is produced by the erythroid elements in the bone marrow. Under the stimulation of erythropoietin, RBC production is increased.


Normally RBCs survive in the peripheral blood for approximately 120 days. During that time the RBC is transported through the bloodstream. In the smallest of capillaries the RBC must fold and bend to conform to the size of these tiny vessels. Toward the end of the RBC’s life, the cell membrane becomes less pliable; the aged RBC is then lysed and extracted from the circulation by the spleen. Abnormal RBCs have a shorter life span and are extracted earlier. Intravascular RBC trauma, such as that caused by artificial heart valves or peripheral vascular atherosclerotic plaques, also shortens the RBC’s life. An enlarged spleen, such as that caused by portal hypertension or leukemia, may inappropriately destroy and remove normal RBCs from the circulation.


Red Blood Cells Count is usually ordered by physicians with both Hemoglobin Levels and Hematocrit Levels. The three tests are used together to give a better idea of how healthy are the patient’s red blood cells. Also the Red Blood Cell count is used with Hemoglobin Levels to calculate the Mean Corpuscular Hemoglobin (MCH) which is a measurement of the body ability to produce Hemoglobin. Red Blood Cell Count is also used with Hematocrit Levels to measure the Mean Corpuscular Volume (MCV) of Red Blood Cells. MCV represents the average size a RBCs.


Red Blood Cell count is measured regularly for patients who have anemia and patients who have ongoing bleeding. Red Blood Cell count can help with Hemoglobin and Hematocrit tests to decide if patients require blood transfusion or not.


Normal RBC values vary according to gender and age. Women tend to have lower values than men, and RBC counts tend to decrease with age. When the value is decreased by more than 10% of the expected normal value, the patient is said to be anemic. Low RBC values are caused by many factors, including:

  1. Hemorrhage (as in GI bleeding or trauma)
  2. Hemolysis (as in glucose-6-phosphate dehydrogenase deficiency, spherocytosis, or secondary splenomegaly)
  3. Dietary deficiency (as of iron or vitamin B12)
  4. Genetic aberrations (as in sickle cell anemia or thalassemia)
  5. Drug ingestion (as of chloramphenicol, hydantoins, or quinidine)
  6. Marrow failure (as in fibrosis, leukemia, or antineoplastic chemotherapy)
  7. Chronic illness (as in tumor or sepsis)
  8. Other organ failure (as in renal disease)


RBC counts greater than normal can be physiologically induced as a result of the body’s requirements for greater oxygen-carrying capacity (e.g., at high altitudes). Diseases that produce chronic hypoxia (e.g., congenital heart disease) also provoke this physiologic increase in RBCs. Polycythemia vera is a neoplastic condition causing uncontrolled production of RBCs.


Like the hemoglobin and hematocrit values, the RBC count can be altered by many factors other than RBC production. For instance, in dehydrated patients the total blood volume is contracted. The RBCs will be more concentrated, and the RBC count will be falsely high. Likewise, in overhydrated patients the blood concentration is diluted and the RBC count per millimeter will be falsely low. In most hospitals and laboratories the RBC count is done by an automated counting machine with an error range of about 4% to 5%.


Causes of False Red Blood Cells Count

Normal Red Blood Count decreases during pregnancy because of the normal changes that occur to the body during pregnancy increase the body fluid increases which dilute the Red Blood Cells. Women also may experience nutritional deficiency while pregnant which is believed to affect the production of Red Blood Cells and cause pregnancy related anemia in some cases.


Living in high altitudes causes increased RBC counts as a result of a physiologic response to the decreased oxygen available at these high altitudes.


Hydration status: As stated above, dehydration factitiously increases the RBC count, and overhydration decreases the RBC count.


Drugs that may cause increased RBC levels include erythropoietin gentamicin, and methyldopa.


Drugs that may cause decreased RBC levels include chloramphenicol, hydantoins, and quinidine.




Normal Red Blood Cell Count

Red Blood Cell cont is measured in terms of Million per Microliter. Red Blood Cell count, and White Blood Cell Count as well,  are the highest in newborns then they decrease dramatically during the first 2 weeks and continue decreasing during the first year. After the first Red Blood Cell count increases again as the child grows. Adult males normally have higher Red Blood Cells Count than adult females. The following is the Normal Red Blood Cells count for distinct age groups:


Newborn: 4.8 to 7.1 Millions/μL.


2 to 8 Weeks of Age: 4 to 6 Millions/μL.


2 to 6 Months of Age: 3.5 to 5.5 Millions/μL.


6 Months to 1 Year Old : 3.5 to 5.2 Millions/μL.


1 to 18 Years Old: 4 to 5.5 Millions/μL.


Adult Male: 4.7 to 6.1 Millions/μL.


Adult Female: 4.2 to 5.4 Millions/μL.




Causes of High Red Blood Cells Count

Erythrocytosis: The number of RBCs increases as a result of illnesses or as a physiologic response to external situations (e.g., high altitude).


Congenital heart disease: Cyanotic heart diseases cause chronically low PO2 levels. In response, the RBCs increase in number.


Severe chronic obstructive pulmonary disease (COPD): Chronic states of hypoxia cause stimulation of RBC production as a physiologic response to increase oxygen-carrying capacity.


Polycythemia vera: This is a result of the bone marrow inappropriately producing great numbers of RBCs.


Severe dehydration (e.g., severe diarrhea or burns): With depletion of extracellular fluid, the total blood volume decreases, but the number of RBCs stays the same. Because the blood is more concentrated, the number of RBCs per cubic millimeter is increased.


Hemoglobinopathies, Thalassemia trait: In response to the decreased oxygen-carrying capacity of abnormal hemoglobin, more RBCs may be produced to provide adequate oxygen-carrying capacity.




Causes of Low Red Blood Cells Count

Anemia: This is a state associated with reduced RBC numbers. Many different types of diseases are associated with anemia.


Hemoglobinopathy: Patients with hemoglobin disorders or other blood dyscrasias may have a reduced RBC number and survival.


Cirrhosis: This is a chronic state of fluid overload. The RBCs are diluted, and the number of RBCs per cubic millimeter is reduced.


Hemolytic anemia (e.g., erythroblastosis fetalis, hemoglobinopathies, drug-induced hemolytic anemias, transfusion reactions, paroxysmal nocturnal hemoglobinuria): The RBC survival is diminished in hemolytic anemia. The number of RBCs decreases.


Hemorrhage: With active bleeding the number of RBCs decreases. It takes time (several hours), however, for the RBC count to fall. Only if the blood volume is replenished with fluid will the RBC count diminish.


Dietary deficiency: With certain vitamin (B12) or mineral (Iron) deficiencies, the RBC size or number is decreased.


Bone marrow failure: This results in reduced synthesis of RBC.


Prosthetic valves: Prosthetic valves cause mechanical trauma to the RBC. The RBC survival time is shortened and numbers diminish.


Renal disease: Erythropoietin is made in the kidney and is a strong stimulant to RBC production. With reduced levels of erythropoietin, the RBC numbers diminish.


Normal pregnancy: Normally there is increased blood volume during pregnancy because of a chronic state of overhydration. Combined with a relative “malnourished” state, the RBC count per cubic millimeter of blood is diminished.


Rheumatoid/collagen-vascular diseases (e.g., rheumatoid arthritis, lupus, sarcoidosis): Chronic illnesses are associated with reduced production of RBCs.


Hematogic Cancers including:

  • Leukemia.
  • Lymphoma.
  • Multiple Myeloma.
  • Hodgkin disease

There cancers are often associated with bone marrow failure. Bone marrow is where Red Blood Cells and other blood components are produced.