Erythrocyte Count (RBC)

Normal red blood cell (RBC) findings

(RBC × 10⁶/μL or RBC × 10¹²/L [SI units]) ^[1]

Adult/elderly ^[1] :

• Male: 4.7-6.1
• Female: 4.2-5.4

Children ^[1] :

• Newborn: 4.8-7.1
• 2-8 weeks: 4-6
• 2-6 months: 3.5-5.5
• 6 months-1 year: 3.5-5.2
• 1-6 years: 4-5.5
• 6-18 years: 4-5.5

Red blood cell count is elevated in the following conditions: ^[2]

• Hemoconcentration and dehydration

• Stress

• Polycythemia vera ^{[3, 4]}

• Smokers

• High altitude

• Cardiovascular disease ^[5]

• Renal cell carcinoma and other erythropoietin-producing neoplasms

Red blood cell count is decreased in the following conditions: ^[2]

• Anemias ^[5]

• Hemolysis

• Chronic renal failure

• Hemorrhage

• Failure of marrow production

Red blood cell (RBC) count can also be used with MCV to aid in the differential diagnosis between iron deficiency and β- or α-thalassemia trait. Increased RBCs with decreased MCV is suggestive of thalassemia trait. An MCV/RBC ratio of less than 13 suggests thalassemia trait, whereas a ratio of greater than 13 suggests iron deficiency. However, this ratio is not definitive for diagnosis, and more definitive tests should be performed when available. ^[6]

Collection and panel details are as follows:

• Specimen: whole blood, usually collected by venipuncture

• Collection: Ethylenediamine tetraacetic acid (EDTA) tube (purple/lavender top) containing EDTA potassium salt additive as an anticoagulant (see image below) ^[7]

  EDTA Tubes

• Panels: complete blood count (CBC)

Description

Red blood cell (RBC) count is a number of red blood cells per unit volume of blood. RBC count then increases either due to relatively decreased plasma volume such as dehydration/hemoconcentration or due to absolute increase in red blood cell production such as in renal cell carcinoma (due to erythropoietin production) or polycythemia vera. RBC count decreases in anemia or blood loss. See the Interpretation section.

Indications/Applications

Red blood cell count is part of a standard complete blood count (CBC) and is used along with hemoglobin concentration and hematocrit to determine if a patient has anemia, polycythemia, dehydration, or response to treatment related to those conditions. The RBC count usually rises or falls along with hemoglobin or hematocrit.

Considerations

Red blood cell count along with hemoglobin concentration, and hematocrit should be interpreted with cautions because the measurement is relative to plasma volume. Conditions that increase plasma volume such as pregnancy will decrease these values and do not reflect absolute anemia. On the other hand, conditions that decrease plasma volume such as dehydration will increase these values and do not reflect absolute polycythemia.