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What is a CBC Test?
Blog 4 min read
What is a CBC Test?
Feb 18, LabFinder Team

If your doctor has ordered a CBC Test for you, it might have raised some questions in your mind: What is a CBC Test? What is it looking for? And what does it mean that my doctor is requesting one for me? Naturally, understanding the specifics of these types of tests can provide a feeling of comfort at a time when you might otherwise not be feeling your best.

A CBC Test or Complete Blood Count Test—is a common lab procedure that doctors recommend for patients who are sick, or even when a general blood work up is needed to determine a patient’s overall health. This one lab work up administers a panel of tests that actually measures several different things.

To put it simply, a CBC measures the number of blood cells circulating in your bloodstream.  Specifically, this includes your white blood cells (WBC), of which there are five types that all play a roll in fighting against infection; your red blood cells (RBC), which serve to carry oxygen through the blood; your platelets, which are responsible for helping your blood to clot; your hemoglobin, a protein found in red blood cells that also carries oxygen from your lungs to the rest of your blood cells; and finally hematocrit, or the ratio of blood cells to plasma. The test also determines the average size of your red blood cells as well as the variation in size of your red blood cells.

According to the Cleveland Clinic, CBCs are commonly ordered when a patient is showing signs of infection, swelling, excessive or unnecessary bruising or bleeding, or when they are feeling overly weak or fatigued. While some of these conditions require treatment, there are many instances in which changes in diet or medication may entirely alleviate the problem.

CBC (complete blood count) - image2Based on the results of a CBC test, doctors can determine the cause of the patient’s symptoms and the best course of action to address them. High numbers of white blood cells, for example, are indicative of an infection or inflammation, whereas low numbers may mean that you are more susceptible to infection. Abnormalities associated with red blood cells are more often a sign of anemia, indicated by too few red blood cells, or too great a differentiation in the size of your red blood cells. Red blood cells can also reveal difficulties with lung disease, dehydration, iron deficiencies, and a variety of other disorders.

Abnormal CBC tests help diagnose several other things as well including autoimmune conditions, bone marrow failure, and certain types of cancer like Leukemia. CBC tests are also used to monitor a patient’s reactions to certain cancer treatments that are known for lowering blood counts. According to the Cancer Treatment Centers of America, CBCs help doctor’s ensure that their patient’s blood counts are closely monitored during cancer treatment.

So what should you expect when going in for a CBC?

The Mayo Clinic website provides a comprehensive overview of what to expect and how to prepare for the CBC test. Unless the blood being drawn is being used for additional tests, patients can eat and drink normally before the CBC test. Once you arrive at the lab, the healthcare professional will take a sample of blood, usually from the arm at the bend in the elbow. There is no recovery needed from the test, and patients can return to their normal daily activities once it’s complete, unless directed otherwise by their doctor.

CBC tests offer a comprehensive range of information and are a great tool in assessing your health, but don’t hesitate to ask questions about specifics so that you are as informed as necessary as to why the procedure is being done.


LabFinder is a no-cost, online platform for people to easily schedule their medical tests and view results securely. The LabFinder team is passionate about improving the ‘patient and doctor experience’ through better communication, reduce out-of-pocket expenses and making everyone know more about their own medical tests. The mission of LabFinder is simple: we want to be solution to you and get you the test results you deserve so you can make right choices about your health.