Complete Blood Count (CBC)

What is a complete blood count?

A complete blood count or CBC is a blood test that measures many different parts and features of your blood, including:

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    Red blood cells, which carry oxygen from your lungs to the rest of your body

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    White blood cells, which fight infection. There are five major types of white blood cells. A CBC test measures the total number of white cells in your blood. A test called a CBC with differential also measures the number of each type of these white blood cells

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    Platelets, which help your blood to clot and stop bleeding

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    Hemoglobin, a protein in red blood cells that carries oxygen from your lungs and to the rest of your body

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    Hematocrit, a measurement of how much of your blood is made up of red blood

A complete blood count may also include measurements of chemicals and other substances in your blood. These results can give your health care provider important information about your overall health and risk for certain diseases.

Other names for a complete blood count: CBC, full blood count, blood cell count.

Why do I need a complete blood count?

Your health care provider may have ordered a complete blood count as part of your checkup or to monitor your overall health. In addition, the test may be used to:

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    Diagnose a blood disease, infection, immune system and disorder, or other medical conditions

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    Keep track of an existing blood disorder

What do the results mean?

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A CBC counts the cells and measures the levels of different substances in your blood. There are many reasons your levels may fall outside the normal range. For instance:

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    Abnormal red blood cell, hemoglobin, or hematocrit levels may indicate anemia, iron deficiency, or heart disease

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    Low white cell count may indicate an autoimmune disorder, bone marrow disorder, or cancer

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    High white cell count may indicate an infection or reaction to medication

If any of your levels are abnormal, it does not necessarily indicate a medical problem needing treatment. Diet, activity level, medications, a women's menstrual cycle, and other considerations can affect the results. Talk to your health care provider to learn what your results mean.

Is there anything else I need to know about a complete blood count?

A complete blood count is only one tool your health care provider uses to learn about your health. Your medical history, symptoms, and other factors will be considered before a diagnosis. Additional testing and follow-up care may also be recommended.

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References

References

1. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998-2017. Complete Blood Count (CBC): Overview; 2016 Oct 18 [cited 2017 Jan 30]; [about 3 screens]. Available 

2. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998-2017. Complete Blood Count (CBC): Results; 2016 Oct 18 [cited 2017 Jan 30]; [about 8 screens]. Available 

3. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998-2017. Complete Blood Count (CBC): Why it's done; 2016 Oct 18 [cited 2017 Jan 30]; [about 5 screens]. Available 

4. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: complete blood count [cited 2017 Jan 30]; [about 3 screens]. Available 

5. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Types of Blood Tests; [updated 2012 Jan 6; cited 2017 Jan 30]; [about 5 screens]. Available

6. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Risks of Blood Tests? [updated 2012 Jan 6; cited 2017 Jan 30]; [about 5 screens]. Available 

7. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Do Blood Tests Show? [updated 2012 Jan 6; cited 2017 Jan 30]; [about 5 screens]. Available 

8. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What To Expect with Blood Tests; [updated 2012 Jan 6; cited 2017 Jan 30]; [about 5 screens]. Available  

9. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Your Guide to Anemia; [cited 2017 Jan 30]; [about 9 screens]. Available

The medical information provided is for informational purposes only and is not to be used as a substitute for professional medical advice, diagnosis or treatment. Please contact your health care provider with questions you may have regarding medical conditions or the interpretation of test results.