CBC blood test
A complete blood count (CBC) test measures the following:
The number of white blood cells (WBC count)
The number of red blood cells (RBC count)
The number of platelets
The total amount of hemoglobin in the blood
The fraction of the blood composed of red blood cells (hematocrit)
The CBC test also provides information about the following measurements:
Mean red blood cell volume (MCV)
Mean hemoglobin amount per red blood cell (MCH)
The mean amount of hemoglobin relative to the size of the cell (hemoglobin concentration) per red blood cell (MCHC)
A blood sample is needed.
There is no special preparation needed.
When the needle is inserted to draw blood, you may feel moderate pain. Some people feel only a prick or stinging. Afterward there may be some throbbing or slight bruising. This soon goes away.
A CBC is a commonly performed lab test. It can be used to detect or monitor many different health conditions. Your health care provider may order this test:
If you are having symptoms, such as fatigue, weight loss, fever or other signs of an infection, weakness, bruising, bleeding, or any signs of cancer
When you are receiving treatments (medicines or radiation) that may change your blood count results
To monitor a long-term (chronic) health problem that may change your blood count results, such as chronic kidney disease
Blood counts may vary with altitude. In general, normal results are:
RBC count:
Male: 4.7 to 6.1 million cells/mcL
Female: 4.2 to 5.4 million cells/mcL
WBC count:
4,500 to 10,000 cells/mcL
Hematocrit:
Male: 40.7% to 50.3%
Female: 36.1% to 44.3%
Hemoglobin:
Male: 13.8 to 17.2 gm/dL
Female: 12.1 to 15.1 gm/dL
Red blood cell indices:
MCV: 80 to 95 femtoliter
MCH: 27 to 31 pg/cell
MCHC: 32 to 36 gm/dL
Platelet count:
150,000 to 450,000/dL
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
High RBC, hemoglobin, or hematocrit may be due to:
A lack of enough water and fluids, such as from severe diarrhea, excessive sweating, or water pills used to treat high blood pressure
Kidney disease with high erythropoietin production
Low oxygen level in the blood for a long time, most often due to heart or lung disease, chronic carbon monoxide exposure, or living at a high altitude
Polycythemia vera
Smoking
Use of testosterone
Low RBC, hemoglobin, or hematocrit is a sign of anemia, which can result from:
Blood loss (either sudden, or from problems such as heavy menstrual periods over a long time)
Bone marrow failure (for example, from radiation, infection, or tumor)
Breakdown of red blood cells (hemolysis)
Cancer and cancer treatment
Certain long-term (chronic) medical conditions, such as chronic kidney disease, ulcerative colitis, or rheumatoid arthritis
Iron deficiency
Leukemia
Long-term infections such as hepatitis
Poor diet and nutrition, causing too little iron, folate, vitamin B12, or vitamin B6
Multiple myeloma
A lower than normal white blood cell count is called leukopenia. A decreased WBC count may be due to:
Alcohol abuse and liver damage
Autoimmune diseases (such as systemic lupus erythematosus)
Bone marrow failure (for example, due to infection, tumor, radiation, or fibrosis)
Chemotherapy medicines used to treat cancer
Disease of the liver or spleen
Enlarged spleen
Infections caused by viruses, such as mono or AIDS
Medicines
A high WBC count is called leukocytosis. It can result from:
Certain medicines, such as corticosteroids
Infections
Diseases such as lupus, rheumatoid arthritis, or allergy
Leukemia
Severe emotional or physical stress
Tissue damage (such as from burns or a heart attack)
A high platelet count may be due to:
Bleeding
Diseases such as cancer or blood disease
Iron deficiency
Problems with the bone marrow
A low platelet count may be due to:
Disorders where platelets are destroyed
Pregnancy
Enlarged spleen
Bone marrow failure (for example, due to infection, tumor, radiation, or fibrosis)
Chemotherapy medicines used to treat cancer
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
Excessive bleeding
Fainting or feeling lightheaded
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
RBCs transport hemoglobin which, in turn, carries oxygen. The amount of oxygen received by body tissues depends on the amount and function of RBCs and hemoglobin.
WBCs are mediators of inflammation and the immune response. There are various types of WBCs that normally appear in the blood:
Neutrophils (polymorphonuclear leukocytes)
Band cells (slightly immature neutrophils)
T-type lymphocytes (T cells)
B-type lymphocytes (B cells)
Monocytes
Eosinophils
Basophils
Lin JC, Benz Jr. EJ. Approach to anemia in the adult and child. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 35.
Means RT. Approach to the anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 149.
Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 31.
Schedule An Appointment
Contact Atlanta Obsetrics and Gynaecology at The Womens Center Millennium Hospital - 404-ATL-BABY
GO
Review Date:
10/16/2022
Reviewed By: Mark Levin, MD, Hematologist and Oncologist, Monsey, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
-
© 1997-2024
All rights reserved.