Vitamin D is mainly used to prevent or treat rickets, which can lead to toxicity when taken in large quantities or for long periods of time by children. Mild poisoning will appear nausea, vomiting, poor appetite, anorexia and other digestive disorders. It can also cause mental abnormalities such as baby irritability, crying and sleep disturbance. Long-term use will lead to calcium salt deposition leading to bone calcification, serious will also lead to the respiratory system, cardiovascular system to produce calcification foci and other chronic diseases, calcium salt deposition serious will cause kidney function damage and other toxic phenomena.