Anemia is a blood disorder marked by a decreased amount of red blood cells (RBCs). People with anemia have insufficient hemoglobin, a protein in red blood cells that carries oxygen through the body.anemia Screening. The complete blood count (CBC) is an essential part of anemia testing. This test measures different types of cells in the blood. It is often used as part of a routine check-up and in diagnosing health problems, and it can reveal the presence of anemia. The CBC analyzes the amount of various blood cells as well as a protein called hemoglobin in the blood.