Rickets, also known as vitamin D deficiency rickets, is a chronic nutritional disease characterized by bone lesions, caused by insufficient vitamin D in a child's body, leading to disrupted calcium and phosphorus metabolism. Typically, it is evident in the incomplete mineralization of the growing long bones' metaphyseal ends and bone tissue, resulting in the softening or deformation of the bones. All children, including full-term infants after two weeks, premature infants, twins, and low birth weight infants after one week, should start supplementing with vitamin D. This is because the content of vitamin D in foods, such as breast milk or various infant formulas, is not sufficient to meet the needs of children. Therefore, a lack of timely vitamin D supplementation after birth can lead to a deficiency and consequently rickets, a disease caused by a lack of vitamin D. (Please use medication under the guidance of a professional physician, and do not medicate blindly.)