Vitamin D deficiency rickets is one of the four major diseases that began to be prevented in the early days of our country. However, more than half a century has passed, the incidence of rickets remains high. The reasons for this are many. When you see that the baby has “occipital baldness, square cranium, rib cage exostosis”, parents will be shocked when they say that this is rickets, and when they tell him that it is “calcium deficiency”, they will be very frank, or very relaxed and unconcerned look. As a result, the signs of rickets are obvious, and the prevalence of colds and other illnesses is higher in these babies than in those who take vitamin D supplements on time. It is very important to take vitamin D or vitamin AD (cod liver oil) on time for your baby’s bone development and resistance. Whether breastfed or artificially fed, start taking it orally 2 weeks after birth, at least until 2 weeks of age. Take it orally continuously without interruption. Some doctors or pharmacists tell parents that taking vitamin AD orally often can be toxic, and that sun exposure in the summer is fine. In fact, not many people really get sun exposure, and there is no definitive answer as to how long sun exposure and how much skin area can be exposed to meet the needs of the body, not to mention the risk of skin cancer caused by ultraviolet light. At present, the ratio of vitamin AD, A:D = 3:1, according to the instructions of long-term use will not be toxic. There are separate vitamin D on the market, but it is better to take the ones containing AD, not only to promote bone development and calcium absorption, but also to enhance resistance (some babies, repeated respiratory infections, may be vitamin A deficiency) and help prevent iron deficiency anemia. Calcium supplementation in general, breast-fed babies 4-6 months to start supplementation. Those who are artificially fed (drink formula) may not take calcium supplements. Some babies, supplemented with cod liver oil, still appear rickets signs, indicating: 1, did not take the medication on time 2, insufficient dose (or insufficient content) 3, poor absorption 4, not calcium supplementation 5, relatively rare: familial hypophosphatemia, renal tubular acidosis, renal rickets — need to go to the hospital.