Low hemoglobin, commonly referred to as anemia, refers to the concentration of red blood cell protein in peripheral blood that is below the normal range. There are three most common causes: 1. Reduced erythropoiesis: The so-called reduced erythropoiesis is caused by various causes of impaired erythropoiesis, most commonly aplastic anemia and some congenital bone marrow failure, etc., which can lead to impaired erythropoiesis. In addition, there are also anemia caused by insufficient raw materials, such as iron deficiency anemia, such as megaloblastic anemia, etc., which leads to a decrease in erythropoiesis; 2, too much destruction of red blood cells: diseases that destroy too many red blood cells, usually such as hemolytic anemia, or serum sickness, thalassemia, etc.; 3, too much loss: blood loss anemia is very common in daily life, especially in women. Excessive menstruation often lost, a large amount of blood can also cause a shortage of raw materials, causing anemia. For example, hemorrhoids in men, there are some tumors or ulcers of the digestive tract can cause the loss of red blood cells. Therefore, once you have symptoms of anemia, it is important to consult a doctor as soon as possible to identify the cause and treat it early.