Red blood cells are the most numerous blood cells in the human body and contain hemoglobin, which can combine with oxygen inhaled into the alveoli to form oxyhemoglobin, which is then transported to various tissues and organs, where the hemoglobin is separated from the oxygen and the oxygen is used by the tissues and organs. Hemoglobin then combines with the carbon dioxide produced by the tissues and organs to form carboxyhemoglobin, which is then transported to the alveoli and expelled from the body through respiration, so the main role of human red blood cells is to transport hemoglobin and oxygen. Because of this, if the number of red blood cells decreases, the concentration of hemoglobin decreases, the body’s ability to transport oxygen and carbon dioxide decreases, which causes the body to lack oxygen and produce less energy, and symptoms such as fatigue and weakness, panic, chest tightness, and limb weakness will occur. If the number of red blood cells is too much, it is easy to produce the condition of blood cell stasis, which is prone to thrombotic diseases, and too many or too few red blood cells are abnormal.