Generally speaking, children can take vitamin D3 until they are about two weeks old, because children grow and develop particularly rapidly before they are two years old, and if parents do not pay attention to giving children vitamin D supplements, it can cause children to develop vitamin D deficiency rickets. After the occurrence of vitamin D deficiency rickets, it will cause children to have occipital baldness, head sweating more, chicken chest, rib beads, and even cause X-shaped legs, O-shaped legs and other adverse reactions, which is very unfavorable to the health of children. And this is the time to give children timely supplementation of vitamin D3, can effectively prevent the occurrence of vitamin D deficiency rickets, and children after two weeks of age, food intake is relatively rich, most can meet the demand for vitamin D, this time can be without vitamin D.