Babies in their third month of life generally do not need to take extra calcium supplements, if necessary, follow the doctor’s instructions for medication. The appropriate intake of calcium for infants aged 0~6 months is 200 mg/d. Since the average calcium concentration of human milk is 291 mg/L and the calcium content of infant formula is 405~650 mg/L, both human milk and infant formula can meet the calcium intake for prevention of nutritional rickets in infants. The food of three-month-old baby is only breastmilk or formula, breastmilk and formula are rich in calcium, protein, carbohydrates, fat and other nutrients, which can satisfy baby’s growth and development and daily energy needs without additional calcium supplements, and oversupplementation of calcium supplements may also increase the burden on the child’s kidneys and damage renal function. Therefore, healthy babies do not need to take extra calcium supplements. Formula and breast milk are good sources of calcium, which are safe and easy to be absorbed. If necessary, calcium supplements should be used under the guidance of a doctor.