There is no “best and fastest” way to replenish blood, and active treatment should be directed at the cause of the disease. Low hemoglobin may be caused by malnutrition, iron-deficiency anemia, malignant tumors, leukemia and other reasons. 1. malnutrition: this is the most common factor, you can take oral blood-saving treasure under the guidance of the doctor, usually pay attention to diet and nutrition. 2. Iron deficiency anemia: the body’s intake of iron is too low and cause less hemoglobin production, you need to take oral iron, such as iron dextrose, ferrous fumarate and other medications, dietary iron rich foods, such as spinach, pig liver, longan and so on. 3. Malignant tumor: malignant tumor will affect the hematopoietic system, and the growth of cancer cells needs to absorb nutrients, which will cause low hemoglobin, and need to be treated mainly by surgery, radiotherapy (carboplatin), etc., and actively correct the anemia, for example, use of vitamin B12 and folic acid. 4. Leukemia: such as acute myeloid leukemia needs to be given cytarabine, zorubicin and other drugs chemotherapy. When hemoglobin value is lower than normal reference value, it can also be seen in other conditions, such as systemic lupus erythematosus, severe liver disease, etc., we should pay attention to it, and actively check the reasons for this situation, receive corresponding treatment under the guidance of physicians for the reasons, and review hemoglobin on a regular basis.