Calcium, iron and zinc are generally not recommended to be supplemented at the same time, especially because calcium and zinc are divalent ions, which can easily compete for the absorption channels in the body and thus affect each other’s absorption. In addition, iron supplements are generally recommended to be taken half an hour before meals because they are likely to cause gastrointestinal reactions such as stomach discomfort and vomiting, so they are not recommended to be taken at the same time as other drugs. When a child is deficient in trace elements, he or she may suffer from loss of appetite, depression, picky eating and partial eating, so it is best to go to the hospital for trace element testing to clarify what is lacking and then what is missing.