Complete Blood Count

 Complete Blood Counts

Overview

A complete blood count (CBC) is a blood test used to evaluate your overall health and detect a wide range of disorders, including anemia, infection and leukemia.

A complete blood count test measures several components and features of your blood, including:

• Red blood cells, which carry oxygen
• White blood cells, which fight infection
• Hemoglobin, the oxygen-carrying protein in red blood cells
• Hematocrit, the proportion of red blood cells to the fluid component, or plasma, in your blood
• Platelets, which help with blood clotting

Abnormal increases or decreases in cell counts as revealed in a complete blood count may indicate that you have an underlying medical condition that calls for further evaluation.

Why it's done

A complete blood count is a common blood test that's done for a variety of reasons:

• To review your overall health. Your doctor may recommend a complete blood count as part of a routine medical examination to monitor your general health and to screen for a variety of disorders, such as anemia or leukemia.
• To diagnose a medical condition. Your doctor may suggest a complete blood count if you're experiencing weakness, fatigue, fever, inflammation, bruising or bleeding. A complete blood count may help diagnose the cause of these signs and symptoms. If your doctor suspects you have an infection, the test can also help confirm that diagnosis.
• To monitor a medical condition. If you've been diagnosed with a blood disorder that affects blood cell counts, your doctor may use complete blood counts to monitor your condition.
• To monitor medical treatment. A complete blood count may be used to monitor your health if you're taking medications that may affect blood cell counts.

How you prepare

If your blood sample is being tested only for a complete blood count, you can eat and drink normally before the test. If your blood sample will be used for additional tests, you may need to fast for a certain amount of time before the test. Your doctor will give you specific instructions.

What you can expect

For a complete blood count, a member of your health care team takes a sample of blood by inserting a needle into a vein in your arm, usually at the bend in your elbow. The blood sample is sent to a lab for analysis. You can return to your usual activities immediately.

Results

The following are normal complete blood count results for adults:

Red blood cell count	Male: 4.35-5.65 trillion cells/L* (4.32-5.72 million cells/mcL**) Female: 3.92-5.13 trillion cells/L (3.90-5.03 million cells/mcL)
Hemoglobin	Male: 13.2-16.6 grams/dL*** (132-166 grams/L) Female: 11.6-15 grams/dL (116-150 grams/L)
Hematocrit	Male: 38.3-48.6 percent Female: 35.5-44.9 percent
White blood cell count	3.4-9.6 billion cells/L (3,400 to 9,600 cells/mcL)
Platelet count	Male: 135-317 billion/L (135,000 to 317,000/mcL) Female: 157-371 billion/L (157,000-371,000/mcL)

• * L = liter
• ** mcL = microliter
• *** dL = deciliter
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