Three month old babies can take vitamin AD drops as a supplement. Vitamins A and D are essential for human growth and development, especially for the development of infants and children, the integrity of epithelial tissue, vision, the constancy of blood calcium and phosphorus, and the development of bones and teeth. In case of vitamin D deficiency, a 3-month-old baby may experience restless sleep at night, excessive sweating, easy startling, and occipital baldness, which are early manifestations of rickets, and then in severe cases, abnormal bone development may occur.