The rapid growth of children, especially at the age of three years, and the rapid growth in height and weight gain can lead to a relative physiologic deficiency of calcium, which can manifest itself as a calcium deficiency. Calcium deficiency has an important effect on growth and development. The main manifestations of calcium deficiency in three-year-old children are as follows: first, easy to wake up, especially during sleep, clinically known as irritability, generally due to low calcium caused by children’s increased excitability, a slight stimulus can affect the child’s sleep. At the same time, due to the child’s sleep is not good, the head repeatedly rubbing the pillow will appear in the pillow baldness, or even sweat, resulting in wet pillow. Secondly, due to calcium deficiency, children are usually prone to picky eating, anorexia, and growth retardation, which is mainly manifested in the growth and development of teeth and the nervous system, which is obviously slower than that of children of the same age. At the same time, the child may cry, disobedience, hair loss and other phenomena. The above situation can also be seen in normal babies. Thirdly, with the aggravation of calcium deficiency, it can cause abnormal development of ribs, commonly known as rib ectropion, chicken chest, and in the process of walking, the lower limbs due to the softer bones, easy to appear O-shaped legs and X-shaped leg deformity. If the above symptoms occur, the child should be given calcium supplements in a timely manner. In addition to the normal diet, the child should drink more milk and take additional calcium supplements, including calcium gluconate and other calcium supplements. It is also a good idea to have your child tested for trace elements to see if there are any other trace element deficiencies at the same time, which should be supplemented as well. Vitamin AD should also be supplemented at the same time.