Anemia can lead to hypoxia, and hypoxia can have an effect on all organs. Hemoglobin is usually below 70g/L for more than six months, which may cause irreversible damage to the heart, such as hypertrophy and enlargement of the heart chambers, and with increasing age may have a higher percentage of heart failure than normal, and a higher chance of arrhythmia, because hypoxia is present for organ and kidney damage. If anemia is more severe it may also affect pregnancy and gestation in women of childbearing age, and the effects on the fetus are incalculable. In children, it can affect growth and development. Because there are many different causes of anemia, different causes of anemia cause different damage to patients, such as iron deficiency anemia is caused by gastrointestinal tumors, and long time may early gastrointestinal tumors become advanced and fatal to patients.