Vitamin AD is not calcium, vitamin AD and calcium preparations are two kinds of drugs, are commonly used in infants and young children, the description is as follows: 1, vitamin AD drops (cod liver oil): clinically commonly used in children under two years of age, can prevent and treat vitamin AD deficiency. Vitamin A and vitamin D are essential substances for human growth and development, especially for the development of fetus and infants, the integrity of epithelial tissues, vision, reproductive organs, the constancy of blood calcium and blood phosphorus, and the growth and development of bones and teeth.2. Calcium preparations: commonly used in clinical practice, such as calcium carbonate, calcium gluconate, calcium citrate, etc., are mainly used for the prevention and treatment of calcium deficiency in children and adults. Vitamin AD combined with calcium preparations are often used to prevent rickets in children.