Calcium supplements are not routinely needed for 4-month-old babies. If it is a normal intake of formula, the calcium provided by the formula itself should be sufficient for a 4-month-old child as long as the baby can eat enough, and breast milk is currently considered to be able to meet the growth and development needs of a 4-month-old child. But after all, the growth rate of each child and the differences in receiving sunlight, the season of birth, the north and south places of birth, etc. are different. Therefore, if a 4-month-old child is assessed by a doctor to have signs of calcium deficiency, such as restless sleep, easy startling and other signs of calcium deficiency, he or she should take calcium supplements when needed.