The need for blood transfusion in patients with anemia is related to the rate of occurrence of anemia, the concentration of hemoglobin, the degree of tolerance of the body to anemia, and the expected duration of treatment of anemia, sometimes requiring transfusion and sometimes not, as follows: 1. Need for transfusion: If the anemia is caused by acute hemorrhage, blood transfusion is needed as soon as possible to replace the lost blood volume. If chronic blood loss results in a hemoglobin concentration <60 g/L, transfusion is also indicated. 2. No transfusion needed: If the anemia is caused by chronic blood loss, emergency blood transfusion is usually not needed. If the hemoglobin concentration is above 60g/L, blood transfusion is not required. If it is iron deficiency anemia, megaloblastic anemia, etc., usually after 1-2 weeks of treatment, the anemia will improve and blood transfusion is usually not needed.