Your blood is composed of many different elements or components, and each performs a specific function. For example, red blood cells (also called RBCs or erythrocytes) carry oxygen to the organs. A key part of the red blood cell is hemoglobin, the molecule that transports oxygen within the red cell. A low hemoglobin or red blood cell count signals anemia. The hematocrit is the percentage of the blood volume that is made up of red cells and is usually around 40-45 percent. The hemoglobin and hematocrit value are two essential numbers your doctor considers when evaluating you for anemia. These are numbers with which you should be familiar.
White blood cells (also called WBCs or leukocytes) fight infection. If there is a high white blood cell count, it may indicate infection. A low white blood cell count may signal a reduced ability to fight infection or disease and may be seen as a result of medications such as chemotherapy, or indicate a problem with your bone marrow.
Platelets are the blood element or component that helps initiate clotting. If the platelet count is low (also called thrombocytopenia), the blood may not clot normally, placing a person at increased risk for bleeding. A high platelet count is called thrombocytosis. Thrombocytosis may occur as a response to inflammation or iron deficiency, or as part of a bone marrow abnormality. Thrombocytosis may be associated with an increased risk for abnormal clotting or thrombosis.
Plasma, the liquid part of your blood, makes up about 60 percent of the blood volume. Plasma consists of water, proteins, and other chemicals such as hormones, antibodies, enzymes, glucose, fat particles, salts, and electrolytes.
You may have heard about clotting factors 8 and 9 with respect to hemophilia. In fact, there are many more clotting factors in plasma. Your doctor may measure levels of different clotting factors if you have abnormal bleeding or conditions such as von Willebrand’s disease. Other tests your doctor may order that evaluate your blood’s clotting capacity include the prothrombin time (PT) and partial thromboplastin time (PTT).