Red blood cell below normal value indicates anemia, which can cause nervous system, digestive system, xenophagia and other diseases. 1. Neurological disorders: anemia can cause insufficient blood and oxygen supply to the brain nerves, thus causing dizziness, headache, forgetfulness, insomnia, tinnitus and other symptoms. 2. Digestive system diseases: Anemia patients will have indigestion, loss of appetite and other symptoms. 3. Pagetism: If the red blood cells are low due to iron, the patient may suffer from pagetism. Because when the human body lacks iron, the activity of cytochrome oxidase in the buccal mucosa will be reduced, which will lead to heterophagic behavior. If low red blood cells are caused by iron deficiency anemia, it can also result in nails that are raised around the perimeter and collapsed in the center, with a shape that resembles a small spoon, and tongue infections. In case of low red blood cells, it is recommended to go to the hospital in time for early and regular treatment so as to avoid any adverse effects.