There is no definite time limit on how old a baby should start taking calcium supplements, and the timing of calcium supplements may vary depending on the needs of each baby. If there are no symptoms of calcium deficiency, there is no need to take additional supplements. If symptoms of calcium deficiency appear, calcium supplements can be taken as prescribed by the doctor. Vitamin D supplementation is recommended after birth for preterm infants, and for term infants starting at about two weeks of age, mainly to promote phosphorus and calcium absorption. Therefore, from the neonatal period to infancy, oral vitamin D can also satisfy the body’s need for calcium and promote bone growth. If your baby does not show symptoms of calcium deficiency before one year of age, additional supplementation is usually not needed. If there are symptoms of calcium deficiency, such as sleep disturbance, sweating, etc., you can improve the urine calcium, serum vitamin D level and other related tests, if necessary, under the guidance of the doctor in a timely manner to supplement calcium supplements, such as calcium gluconate and so on. In addition, babies need to strictly follow the doctor’s instructions when supplementing calcium, calcium supplementation should not be excessive, in order to prevent adverse reactions.