In order to prevent calcium deficiency and rickets in children, our pediatricians have discussed and formulated a unified prevention program for infancy and early childhood: 1. advocate breastfeeding and timely addition of complementary foods to ensure that children’s needs for various nutrients, artificial feeders should use infant formula; 2. start sunbathing as early as possible (2-3 weeks after birth), the average daily should be more than 1 hour; 3. full-term children 2 weeks after birth start daily Vitamin D supplementation of 400 IU per day until 2 years of age. 4. For frail children or in winter and spring, the general vitamin D requirement is 400-800 IU. Pediatricians in the United States recommend adding 200 IU of vitamin D daily in the following cases: 1. breast-fed or mixed-fed children with less than 500 ml of formula per day; 2. artificially fed children with less than 500 ml of formula per day. Therefore, it can be seen that how to add vitamin D is related to the feeding method (breast milk? mixed? artificial?) , the amount of milk, the season and the region. For example, for exclusively breastfed infants, 400 IU of vitamin D should be supplemented daily, which can be reduced in summer when there is sufficient sunlight; while mixed and artificially fed children should be adjusted according to the daily intake of formula milk and the amount of fortified vitamin D in the corresponding formula milk, and if there are many outdoor activities and sufficient sunlight in summer, no additional vitamin D supplementation can be given, and attention should be paid to vitamin D supplementation in winter. In addition, if the daily amount of formula is less than 500 ml, additional vitamin D supplementation is also required. Through the above discussion, parents have already understood the principles and methods of vitamin D supplementation, but each child has individual differences, you should also take your child to a specialized medical institution or professional children’s health examination agency for regular checkups and ask your doctor to evaluate and guide your child so as to ensure your child’s healthy growth.