The methods of determining the amount of gastrointestinal bleeding usually include two major categories, the first type of rough estimation method, the initial estimation is also based on clinical symptoms. If the stool routine indicates positive occult blood, it suggests that the bleeding volume is around 5mL/24h, and if it is tarry stool or dark red blood, the bleeding volume is around 300-400mL per day. However, the estimation of bleeding volume by clinical symptoms is usually not very consistent with the actual bleeding, so the second type of more accurate estimation method is chosen clinically, which is to closely monitor the hemoglobin in the routine blood, generally speaking, the normal hemoglobin is in the range of 120-140g/L, if every 10g/L decrease means the bleeding volume is around 400mL.