A complete blood count, or CBC, includes the white blood cell count, red blood cell count, hematocrit, hemoglobin and platelet count. A CBC is a common blood test to diagnose and monitor a variety of medical conditions. There are many diseases and conditions that can cause a low CBC, of which some are mild and easily treated, and others may be severe and potentially fatal.
White Blood Cell Count
A normal white blood cell count, or WBC, is 4,500 to 10,000 cells/mcL, reports MedlinePlus. Autoimmune diseases such as systemic lupus erythematosus, in which the body's normal immune response cannot differentiate between harmful and healthy substances, can cause a low WBC known as leukopenia.
Other possible causes for a low WBC include a diseased liver or spleen and bone marrow failure due to an infection, radiation or tumor. Treatment options for a low WBC include identifying the underlying cause along with symptomatic support for fatigue. A low WBC reduces the body's immune defenses and increases the potential for susceptibility to infections.
Red Blood Cell Count
Red blood cell count, or RBC, is the part of the complete blood count that can identify the number of RBCs in the blood and how much oxygen is delivered through the blood stream. Normal values for men range from 4.7 to 6.1 million cells/mcL and from 4.2 to 5.4 million cells/mcL for women, as reported by the University of Maryland Medical Center.
Possible causes for a low RBC count include anemia, leukemia, malnutrition, hemorrhage, bone marrow failure, pregnancy and overhydration. Medications that can reduce the RBC count include quinidine, chloramphenicol and hydantoin.
Hematocrit
The hematocrit reading, or Hct, in a CBC is the number and size of RBCs as a percentage found in whole blood. Normal Hct values range from 40.7 to 50.3 percent for men and from 36.1 to 44.3 percent for women, reports the UCSF Medical Center.
Possible causes for a low Hct reading include hemorrhage, leukemia, anemia, bone marrow failure, rheumatoid arthritis, multiple myeloma and malnutrition.
Hemoglobin
Hemoglobin, or Hgb, a protein in red blood cells, carries oxygen to all the cells in the body. Normal Hgb results for men range from 13.8 to 17.2 mg/dL and 12.1 to 14.1 gm/dL for women, reports the University of Maryland Medical Center.
Possible causes for a low Hgb level include aplastic anemia, cancer, cirrhosis, Hodgkin's lymphoma, non-Hodgkin's lymphoma, leukemia, multiple myeloma and vitamin deficiency anemia, states MayoClinic.com.
Platelet Count
A low platelet count, or thrombocytopenia, is an abnormally low amount of the blood-clotting particles in the blood. The Merck Manual of Health and Aging reports the normal range for platelet count is between 150,000 and 350,000 per microliter of blood. Platelet readings below 20,000 can be life-threatening.
Possible causes for a very low platelet count include leukemia, low production of platelets by the bone marrow, lymphomas and HIV, or human immunodeficiency virus infection. Anticoagulant medications, such as heparin, can cause a low platelet count.
