What is a CBC?
The CBC measures the number of blood cells and related components in circulating blood. Specifically, the CBC measures the number of red blood cells, white blood cells, and platelets present in the peripheral blood, which is the blood that travels through the veins and capillaries. They all have different functions, and in normal, healthy individuals, they are relatively constant in number.
It also measures the level of hemoglobin, which is a protein within the red blood cell that carries oxygen to tissues and the hematocrit, which is the percentage of red blood cells per total volume of blood, as well as several other measurements related to the red blood cells. These include MCV (mean corpuscular volume), which measures the average volume of the red blood cell; MCH (mean corpuscular hemoglobin), which measures the average amount of hemoglobin within that red blood cell; and MCHC (mean corpuscular hemoglobin concentration), the average percentage of hemoglobin in the red blood cell.
Why would you use this screening test?
It's probably one of the first tests that a doctor orders. What they are looking for depends on what your complaint is. A doctor might recommend a CBC because you have constant fatigue and might be anemic. It is often used to screen for any suspected disease or condition caused by dangerously abnormal changes in cells counts, such as the presence of certain cancers, exposure to certain chemicals, or infections. It's routinely used when you have a hematologic disease such as leukemia or lymphoma, or other blood-related or chronic illness.
