Complete Blood Count (CBC) Test: What It Is, Why It Is Done, and What Results Mean

What is this test? A complete blood count (CBC) is a common blood test that measures the different cells in your blood, including red blood cells, white blood cells, and platelets, to help evaluate your overall health.

The ABCB1 gene c.1236C>T test is a genetic test that looks for a specific change (variant) in your ABCB1 gene. This gene contains instructions for making a protein called P-glycoprotein (P-gp), which acts like a pump to move certain drugs in and out of cells throughout your body. The c.1236C>T variant is one of the most common genetic variations in the ABCB1 gene and can affect how well this protein works.

Why might I need this test? Your healthcare provider may order a CBC as part of a routine checkup, to help find the cause of symptoms such as fatigue, weakness, fever, or unusual bruising, or to monitor a condition like anemia or an infection.

Your doctor may order this test to help predict how you might respond to certain medications. The ABCB1 gene variant can influence how your body processes drugs like some chemotherapy agents, steroids (such as dexamethasone), certain antidepressants, and some heart medications. Knowing your genetic makeup can help your doctor choose the most effective medication or adjust the dose for better treatment outcomes.

How is the test done? A healthcare professional will clean your skin and draw a small sample of blood from a vein in your arm, usually on the inside of your elbow, using a thin needle. The sample is then sent to a laboratory for analysis.

A healthcare professional will collect a small sample of your blood, usually from a vein in your arm. The sample is then sent to a specialized laboratory where scientists analyze your DNA to detect the presence or absence of the c.1236C>T variant in the ABCB1 gene. The results are typically available within a few days to a couple of weeks.

What do the results mean? Your results show whether your red blood cell, white blood cell, and platelet counts fall within normal ranges. Abnormal levels may suggest conditions such as anemia, infection, inflammation, or bleeding problems, and your provider will explain what your specific values mean for your care.

The test result will show whether you have the normal version (wild-type), the variant version, or both (heterozygous) of the ABCB1 gene at position 1236. Having the variant may mean that the P-glycoprotein functions differently in your body, which can affect drug absorption, distribution, and elimination. Your doctor will interpret these results together with your medical history and other factors to guide your treatment plan.