After your baby is determined to have a calcium deficiency, you can improve the condition by taking vitamin D supplements, getting more sunlight, and taking food supplements, but there is no such thing as the best way to replenish calcium. 1. Supplemental vitamin D: supplemental vitamin D can help calcium absorption, you can take oral vitamin D drops under the guidance of a doctor for supplementation. 2. Sunbathing: It is recommended that babies get more sunbathing. The reason for sunbathing to supplement calcium is that the ultraviolet rays in sunlight can promote the synthesis of vitamin D, which in turn promotes calcium absorption. 3. Food supplement: If the baby is breastfed, the mother can eat milk, beans and other high-calcium foods, if the milk powder feeding, you can give the baby to eat calcium-containing milk powder, 6 months after the baby, you can gradually add high-calcium complementary foods, such as fish, eggs and so on.