Vitamin D supplementation is for the prevention of rickets. Most children before the age of two are recommended to take supplementation in the fall and winter, and the probability of rickets generally decreases after the age of two when children have more outdoor activities and a balanced diet. However, if the child has signs and symptoms of rickets, and combined with bone mineral density and trace element testing is indeed hypocalcemia, it is necessary to supplement Iconocin and calcium supplements, the most effective way to prevent rickets is to have more outdoor activities in the sun and a reasonable diet.