Vitamin D is a very important hormone in the body. Vitamin D deficiency in children can cause rickets, which is a specific bone metabolic disease caused by vitamin D deficiency, and patients can manifest as crying at night and poor sleep. For children, the main reason is that vitamin D deficiency leads to a decrease in calcium absorption, resulting in abnormal bone development, especially abnormal development of the scale cartilage of the bones, which may result in bone deformities, such as X-leggedness and O-leggedness. Therefore, children with vitamin D deficiency mainly show symptoms such as crying, excessive sweating at night or short growth, easy fracture and abnormal body shape.