Red blood cells, abbreviated as RBCs, are the most abundant type of blood cells in the human body and have the functions needed to transport oxygen and to transport carbon dioxide. When the number of RBCs is low, the body becomes anemic and the patient shows a series of symptoms such as pallor, dizziness, palpitation, chest tightness, tinnitus, insomnia and forgetfulness. Red blood cells also have hemoglobin inside, which can combine with oxygen to form oxyhemoglobin, then transported to tissues and organs with blood circulation, in which oxygen is separated from hemoglobin for use by the body, while carbon dioxide produced by the body’s tissue cells will combine with hemoglobin to form carboxyhemoglobin, which is transported to the lungs with blood circulation and discharged from the body with breathing. Therefore, red blood cells are the body’s transport machine, which can transport oxygen and carbon dioxide and provide the body with a constant supply of energy.