Low hemoglobin means a decrease in hemoglobin concentration, that is, a condition of anemia. How low the hemoglobin is dangerously low needs to be analyzed specifically with the patient’s specific situation. For example, a healthy adult woman has a short term drop in hemoglobin due to ruptured bleeding from an ectopic pregnancy. Sometimes before the hemoglobin concentration drops to 60 g/L, the patient is already showing symptoms of hemorrhagic shock, manifested by pallor, panic, cold extremities, and decreased blood pressure, and is in considerable danger. If surgical hemostasis is not performed in time, the patient is at risk of shock leading to death. If the hemoglobin concentration is lower than 60g/L, even if the hemoglobin concentration is lower than 60g/L, the patient does not have excessive discomfort and the vital signs are stable because the body has adapted and can tolerate ischemia and hypoxia. In addition to the degree of decrease in hemoglobin concentration, the rate of decrease in hemoglobin concentration should also be considered.