Low mean red blood cell volume is a common clinical condition associated with iron deficiency, such as iron deficiency anemia. Reduced erythrocytes and hemoglobin in the blood count, in addition to low mean red blood cell volume, there is also a reduction in mean red blood cell hemoglobin concentration and mean red blood cell hemoglobin content, which is mainly seen in iron deficiency anemia. It is usually necessary to check ferritin, which is mostly reduced. The main reason for this may be an increased need for iron, or insufficient food intake. In addition, some patients have bleeding or intestinal bleeding, which can cause iron deficiency anemia. In patients with iron deficiency anemia, hemoglobin will soon return to normal after iron supplementation is given. At the same time, the average red blood cell volume can also return to normal by itself.