Bone density screening test is mainly applicable to adults and the elderly, and is more significant for the diagnosis of osteoporosis. Bone age test is mainly used to detect children, through the bone growth, can determine the age of children, height growth, but also can find out whether children have precocious puberty, to facilitate early diagnosis and early treatment. In addition to children, bone age test can also be used for athletes, which helps to determine whether the bone age is advanced or pushed back, and whether there is growth potential. The Z-value of bone density is between 2-(-2), and the specific meaning of Z-value of bone density is the standard deviation of bone density from that of normal people of the same age, which reflects the value of bone density of people of the same age after sampling, and takes the form of standard deviation to reflect the number. Bone density reflects the amount of mineral elements in the body, which is a standard for diagnosing osteoporosis. A baby may have a bone density of 0g/cm^3 at birth, but this does not indicate symptoms of osteoporosis. Usually the bone density test is relatively simple and can be measured by placing the forearm in a machine, which, unlike drawing blood, will not harm the baby. Vitamin D can promote the absorption of calcium, food, milk, eggs, shrimp seafood food if not allergic to eat some as far as possible. In addition to this, you can also sunbathe to make the body’s vitamin D conversion synthesis increase, promote the absorption of calcium, but because the baby’s skin is more delicate, not suitable for a long time in the strong sun exposure.