The Complete Blood Count, or CBC, is one of the most frequently ordered blood tests. It provides a comprehensive overview of the cells that make up your blood: red blood cells, white blood cells, and platelets. This test is a fundamental tool for evaluating your overall health and detecting a wide range of disorders, including anemia, infection, and leukemia.
Red blood cells (RBCs) are responsible for transporting oxygen from your lungs to the rest of your body. The CBC measures several aspects of your red blood cells, including the total RBC count, hemoglobin (the oxygen-carrying protein), and hematocrit (the proportion of your blood volume that consists of red blood cells). Low levels of these markers typically indicate anemia, a condition that can cause fatigue, weakness, and shortness of breath. Anemia can stem from various causes, such as iron deficiency, vitamin B12 deficiency, or chronic disease.
White blood cells (WBCs) are the soldiers of your immune system, defending your body against infections and foreign invaders. The total WBC count gives a general picture of your immune status. An elevated WBC count often suggests an active infection, inflammation, or a response to stress. A low WBC count might indicate a weakened immune system, perhaps due to a viral infection, certain medications, or bone marrow issues. The CBC often includes a "differential," which breaks down the total WBC count into five specific types of white blood cells (neutrophils, lymphocytes, monocytes, eosinophils, and basophils), each with a specialized role in the immune response.
Finally, platelets are tiny cell fragments essential for blood clotting. A low platelet count can lead to excessive bruising or bleeding, while a high count may increase the risk of abnormal blood clots.