Infants should start supplementation within a week after birth. As the child grows older, he or she can choose whether to take cod liver oil again with the advice of a doctor, depending on the child’s health, diet, and exercise level. In case of rickets manifestation, it is necessary to combine with the body’s blood calcium and if necessary, shock therapy and calcium supplementation. In principle, if the blood calcium is normal and the child does not have convulsions, additional cod liver oil supplementation is not recommended because the absorption rate of calcium in milk is still relatively high. Vitamin D can promote the absorption of calcium, so supplementation with vitamin D, i.e. cod liver oil, is sufficient for the general growth of the child. You can stop taking it in the later stages especially when there is more sunlight and more outdoor activities. In winter as well as summer when there is more shade due to too much heat, this is when oral supplementation is recommended. It is best to take it under the guidance of a doctor and prohibit the indiscriminate use of drugs.