Hematology is known as the study of blood regarding health and disease which revolves around issues with red blood cells (RBCs), white blood cells (WBCs), platelets, lymph nodes, blood vessels, bone marrow, and the proteins involved in bleeding and clotting. As biomedical engineers, it is especially vital to understand the mechanics of the various components of blood to avoid unwanted results from implantations such as heart valves. A comprehensive review on the biomechanics of blood is discussed in this chapter. We will also discuss that even though human blood is a non-Newtonian fluid, depending on the instance, it can be considered a Newtonian fluid.