Blood Basics: What is the Complete Blood Count?

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Blood is more than just the red liquid flowing through your veins — it’s a lifeline that fuels every cell, regulates temperature, and defends against diseases.


Blood is vital.


That means that when there’s a problem with your blood, it can affect your overall health. Minor irregularities can signal major health issues, making regular monitoring essential for catching small items before they become bigger problems.


This is where the Complete Blood Count (or CBC) test comes in.

 

What is a Complete Blood Count?

A Complete Blood Count test gives your physician important information about the types and numbers of cells in your blood. A CBC test is normally done as part of your regular physical or your physician may order the test if you are having certain symptoms like fatigue, fever, signs of an infection, or unexplained bruising.


The results of your test are used to both detect and/or identify a variety of hematologic diseases, which are disorders of the blood and blood-forming organs (like bone marrow). Hematologic diseases affect millions of Americans and can range from anemia, genetic disorders, blood cell cancers, HIV and sickle cell disease to complications related to chemotherapy or transfusions. Occasionally even other cancers, like colon and gastrointestinal malignancies, are first detected because of changes in the CBC.

 

What does a Complete Blood Count Test for?

Blood is made up of about 55% blood plasma and about 45% different types of blood cells. The complete blood count tests for that 45% of different blood cells, which includes red blood cells (RBC), white blood cells (WBC), and platelets. A CBC test evaluates for:


      • Red blood cell count
        Red blood cells are responsible for carrying oxygen to and carbon dioxide away from all cells. Low levels may indicate anemia, B12, or iron deficiency, while high levels can be a sign of lung problems, blood cancers, heart disease, kidney disease or genetic disorders.
      • Hematocrit
        Hematocrit measures the amount of space red blood cells take up in the blood. Just like the red blood cell count, low levels may indicate anemia, B12, or iron deficiency, while high levels can be a sign of lung problems, blood cancers, heart disease, kidney disease or genetic disorders.
      • Hemoglobin
        Hemoglobin is a chemical compound inside red cells that transports oxygen through the bloodstream to all cells of the body and gives blood its red color. Since oxygen is needed to maintain healthy organs, this measure is important to measuring full-body health. Like the red blood cell and hematocrit counts, low levels of hemoglobin may indicate anemia, B12, or iron deficiency, while high levels can be a sign of lung problems, blood cancers, heart disease, kidney disease or genetic disorders.
      • Red cell distribution width (RDW)
        Red cell distribution width is a calculation of the variation in the size of your red blood cells. There’s normally no concern with low RDW but a high level could be a sign of anemia.
      • White blood cell count
        White blood cells are the body’s primary defense against disease. White blood cells help fight infection. Either low or high counts of white blood cells could be a result of infections or autoimmune diseases.
      • Platelet count
        Tiny fragments of cells are essential for normal blood clotting. Either low or high levels of platelets could be a result of bone marrow problems, liver disease, or autoimmune conditions.

What do Results Mean?

So, you’ve gotten your CBC test and received your results. Now what?


Normal ranges can vary depending on the laboratory that process the blood, but here is one example of ranges for each component of the test:

The graphic is a table listing out what is tested in the CBC panel and what the normal values are of those tests. The first test is red blood cell count, and the normal value is 3.77 - 5.28 million cells per mcL. The next test is hematocrit, and the normal value is 34% - 46.6%. The next test is hemoglobin, and the normal value is 11.1 - 15.9 g/dL. The next test is red cell distribution width (RDW), and the normal value is 11.7% - 15.4%. The next test is white blood cell count, and the normal value is 3.4 - 10.8 k/mcL. The next test is platelet count, and the normal value is 150 - 450 k/mcL.

*The above normal ranges are based on LabCorp’s CBC reference intervals.

Results slightly outside of the normal range is not necessarily a cause for concern, especially for a healthy individual with no symptoms. However, if your results are abnormally out of range, you should consult with your provider, who might even recommend a visit to a hematologist (a doctor who specializes in diagnosing and treating blood diseases and disorders).

 

It’s important to remember that your physician is the one who can tell you what your results may mean, if there is a cause for concern, and if you may need follow up treatment or not.

The complete blood count test is one of many useful tests that eHealthScreenings offers as an add-on to enhance the basic lipid venipuncture panel, and just one way you can help your employees get a better understanding of their health. As we’ve talked about, blood can tell the story of an individual’s health and being armed with knowledge can help them make better decisions about their health. Contact us, to learn about the additional tests eHealthScreenings offers for both employees and employers.