Vitamin D3 drops can be supplemented with vitamin D. Supplementation usually starts from 15 days after the baby’s birth and is recommended to be taken in the morning half an hour after breastfeeding. If a baby is deficient in vitamin D, the ability of intestinal calcium absorption will be significantly reduced, which will easily cause hypocalcemia. Hypocalcemia will lead to excessive sweating, chicken chest, X-shaped legs, O-shaped legs and so on. Therefore, it is very necessary to start supplementing vitamin D3 drops after 15 days of baby’s birth to ensure that baby’s vitamin D level is sufficient to increase the intestinal calcium absorption ability and maintain the blood calcium level in the normal range. Supplementation of vitamin D3 drops for newborns is usually required until about one and a half years old. It is recommended that babies take it half an hour after breastfeeding in the morning, which can effectively promote calcium absorption. In addition, parents can take the baby out more sunshine, to ensure that 2 hours of sunshine a day, can effectively promote the absorption of calcium, to prevent the occurrence of vitamin D deficiency diseases.