Type of test Blood
Normal findings
(RBC × 106/μL or RBC × 1012/L [SI units])
Adult/elderly
Male: 4.7-6.1
Female: 4.2-5.4
Children
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
Test explanation and related physiology
This test 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 count (CBC).
Intravascular RBC trauma such as that caused by artificial heart valves or peripheral vascular atherosclerotic plaques shortens the life of the RBC. An enlarged spleen such as that caused by portal hypertension or leukemia may inappropriately destroy and remove normal RBCs from circulation.
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 lower than the range of the expected normal value, the patient is said to be anemic. Low RBC values are caused by decreased bone marrow production (e.g., myelofibrosis, leukemia, renal disease, or dietary deficiencies), increased blood loss (e.g., bleeding), or increased RBC destruction (hemolysis).
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.
interfering factors
• Normal decreases are seen during pregnancy because of nor mal body fluid increases and dilution of the RBCs.
• Persons living at high altitudes have increased RBCs.
• Hydration status: Dehydration factitiously increases the RBC count, and overhydration decreases the RBC count.
* Drugs that may cause increased RBC levels include erythropoietin and gentamicin.
* Drugs that decrease RBC levels are many, including those that decrease marrow production or those that cause hemolysis.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: no
• Blood tube commonly used: lavender
• Thoroughly mix the blood with the anticoagulant by tilting the tube.
• Avoid hemolysis.
Abnormal findings
Increased levels
- High altitude
- Congenital heart disease
- Polycythemia vera
- Dehydration or hemoconcentration
- Cor pulmonale
- Pulmonary fibrosis
- Thalassemia trait
- Severe chronic obstructive pulmonary disease
Decreased levels
- Hemorrhage
- Hemolysis
- Anemia
- Hemoglobinopathy
- Advanced cancer
- Bone marrow failure
-Leukemia
- Lymphoma
- Antineoplastic chemotherapy
- Chronic illness
- Renal disease
- Overhydration
-Multiple myeloma
- Pernicious anemia
- Rheumatoid disease
- Subacute endocarditis
-Pregnancy
- Dietary deficiency
- Prosthetic valves
