Red Blood Cell Count (RBC)

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Latest Edit: Hector 2014-03-24 (EDT)

See Also Lab Tests

The red blood cell (RBC) count is closely related to the hemoglobin and hematocrit levels. It is routinely performed as part of the complete blood count.[1], [2]


The test is a count of the number of circulating red blood cells. Normally RBCs survive in the peripheral blood for approximately 120 days. Intravascular RBC trauma, such as that caused by artificial heart valves or atherosclerosis can shorten the lifespan of RBCs. Conditions such as an enlarged spleen, portal hypertension or leukemia may destroy RBCs and decrease the number in the peripheral circulation.

Patient Preparation

  • Fasting is not required for this test.

Interfering Factors:

  • Women tend to have lower values than men.
  • Normal RBC levels decrease during pregnancy.
  • Living in high altitudes may increase RBC levels.
  • Drugs that may cause increased levels include gentamicin and methyldopa.
  • Drugs that may cause decreased levels include chloramphenicol, hydantoins and quinidine.

Clinical Implications

RBC count is primarily used as a test for anaemia, but it can also indicate:

High levels indicate:

Low levels indicate:

  • Anaemia including hemolytic anemia
  • Hemoglobinopathy
  • Cirrhosis
  • Hemorrhage
  • Dietary deficiency
  • Bone marrow failure
  • Renal disease
  • Normal pregnancy
  • Collagen vascular diseases such as rheumatoid arthritis or lupus
  • lymphoma
  • Multiple myeloma
  • Leukemia
  • Hodgkin disease

Associated Tests

A RBC test is typically part of a complete blood count which includes hemoglobin and hematocrit.


  1. Pagana Kathleen D, Pagana Timothy J (2006) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby.
  2. Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain.