High coefficient of variation of erythrocyte width may be due to iron deficiency, vitamin B12 deficiency and folic acid deficiency. 1. Iron deficiency: Due to iron deficiency, most of the red blood cells are small in size. After supplemental iron treatment, the volume of red blood cells begins to increase gradually, while some red blood cells have not increased significantly, so there will be a significantly high coefficient of variation of red blood cell distribution width. 2. Vitamin B12 deficiency: Vitamin B12 deficiency can lead to anemia and low platelet count. Due to the lack of nutritional balance caused by the red blood cell volume of large and small, the more uneven, the higher the value. This will appear red blood cell distribution width coefficient of variation is significantly high. 3. Folic acid deficiency: If folic acid is deficient, megaloblastic anemia will be easily caused, and the coefficient of variation of erythrocyte distribution width will also be obviously high. Higher red blood cell width coefficient of variation needs to be combined with other indicators to make a comprehensive judgment, and it is recommended to go to the hospital in time for a clear examination and treatment under the guidance of the doctor.