This depends on the child's development, and there is no specific time. If parents find that the child has calcium deficiency, such as leg cramps, inattention, night sweats, slow height growth, etc., it is necessary to give the child a reasonable calcium supplement. It's best to choose the one that can supplement calcium to the bone, and the calcium supplement effect is better. Under Baidu, for example, Mommy loves calcium? KD? Tablet, its main components are calcium carbonate and vitamin D? Vitamin k? . Vitamin d? Mainly to promote intestinal absorption of calcium, vitamin K? It can introduce calcium into the bone and really supplement calcium into the bone. Three effects in one, calcium into the bone, better promote bone development.