Anemia is the reduction of red blood cells in the body’s circulation. When less than the normal range, the body’s organ systems will not have enough oxygen, resulting in a series of clinical manifestations. 1. China’s standard for anemia is: adult male hemoglobin <120g/L, adult female hemoglobin <110g/L, pregnant women hemoglobin <100g/L, can be judged as anemia. 2. Clinically, there are many ways to classify anemia, and the commonly used ones are: classified according to the morphology of red blood cells, classified according to the concentration of hemoglobin, classified according to the pathogenesis and etiology, and so on. 3. The most common type of anemia is iron-deficiency anemia, which is mainly caused by chronic blood loss and can be seen in hemorrhoids, peptic ulcer, excessive menstruation in females, and digestive tract tumors. 4. The general manifestations of anemia include weakness, dizziness, palpitation, pale skin and mucous membranes, while each type of anemia also has its own specific manifestations, such as iron-deficiency anemia, the patient may appear heterophagia, dysphagia, spatial nail and other tissues of the iron deficiency manifestations. Different types of anemia have different treatment options. Therefore, if you suspect anemia, you should consult a doctor in time to find out the type and cause of anemia, and cooperate with the doctor for active treatment.