1, the performance of vitamin D deficiency: infants and children show night crying, sweating, sleep restlessness, slow eruption of milk teeth; older children often say leg pain, but can not say the specific location. Some of them show restless sleep, frequent tossing and turning, and excessive sweating. 2.How to further confirm the diagnosis? Many parents go to the hospital and ask for a blood trace element check, but this is actually futile, because the calcium deficiency is usually said to be a bone calcium deficiency, and the blood is usually not low, because there is parathyroid hormone compensation, even if the bone calcium deficiency, blood calcium is often not low. You should also check your blood for 25 hydroxyvitamin D, which is more accurate. Or take an x-ray of the distal end of the long bones, there will be corresponding performance, which can help the diagnosis. 3. Prevention Premature babies and twin-born babies start to take vitamin D supplementation at 800 units per day two weeks after birth, and change to preventive amount at 400 units per day after 3 months; full-term babies start to take vitamin D supplementation at 400 units per day two weeks after life until about 2.5 years old, and older children should also take 2-4 boxes intermittently after entering winter. Betadine or Icocin will do.