During the period of rapid growth and development, babies need to supplement with cod liver oil to ensure effective absorption of calcium from food. Babies should take additional vitamin D from 2-4 weeks after birth to prevent calcium deficiency. The recommended daily dose of vitamin D supplementation is 400-800 international units and continues until about 2 years of age. With the right amount of vitamin D intake, calcium supplements can be added in order to meet the baby’s daily calcium needs, especially for artificially fed babies, and the timing of calcium supplements is basically the same as that of vitamin D supplements. Vitamin D must be supplemented in a timely manner, and calcium can be supplemented slightly later than 1-2 months, especially for breastfed babies. For breastfed babies, if the diet is high in calcium, no additional calcium supplementation is possible, but cod liver oil alone is usually not.