Vitamin D supplementation can be done routinely after 2 weeks of life, because the intake of vitamin D is relatively low when babies are breastfed or fed, and if no attention is paid to vitamin D supplementation, it will often cause babies to develop vitamin D deficiency rickets. After the baby suffers from vitamin D deficiency rickets, there will be more sweating, pillow baldness, rib beading and sleep at night and other symptoms. Because vitamin D has the role of promoting intestinal calcium absorption, vitamin D deficiency will be significantly lower levels of calcium in the blood, so you can give your baby vitamin D, but nothing is absolute, if the blood level of vitamin D is significantly high there is no need to take vitamin D.