Erythrocyte volume refers to the average volume of erythrocytes, the normal value range is 80~100fL, lower than 80fL is the average volume of erythrocytes is low, commonly found in iron deficiency anemia and thalassemia. Ischemic anemia is due to nutrition, chronic blood loss, heredity and other factors, resulting in the lack of iron, one of the raw materials for hematopoiesis in the body, causing the volume of newborn red blood cells to decrease. Thalassemia is a hereditary disease that manifests itself as a reduction in the size of red blood cells due to the absence of the gene that expresses the peptide chain of the pearl protein, which results in the impaired synthesis of the peptide chain of the pearl protein. Both of these disorders can be accompanied by a decrease in mean hemoglobin volume and mean hemoglobin concentration. In addition to the above, there are other conditions that may lead to low mean red blood cell volume, such as iron granulocytic anemia, etc. It is recommended to go to the hospital for examination, and follow the doctor’s instructions for timely and targeted treatment, so as not to delay the course of the disease.