Anemia refers to a clinical syndrome that occurs when the volume of red blood cells in peripheral blood is lower than normal. In clinical practice, anemia is classified into four levels according to hemoglobin concentration: I. Between 90-120g/L belongs to mild anemia. Patients with mild anemia often do not have obvious clinical manifestations, but will only have panic and chest tightness during heavy physical activity. Patients with moderate anemia can show pale complexion and symptoms of panic, chest tightness and shortness of breath after activity. Patients with severe anemia will show obvious symptoms of anemia, pallor is very serious, and they will feel panic and chest tightness after slight activity, accompanied by a series of symptoms such as dizziness, headache, tinnitus, and blurred eyes. Fourth, below 30g/L is severe anemia, in this case, the patient will have obvious symptoms of panic and chest tightness even in a quiet state.