Final answer:
The nurse should instruct the parents to administer the liquid oral iron supplement to their child with iron deficiency anemia using a straw to avoid teeth staining and to not mix it with cereal or formula, avoiding mealtimes for better absorption.
Step-by-step explanation:
When instructing the parents of a child with iron deficiency anemia on the administration of a liquid oral iron supplement, it is important to make sure the iron is absorbed as effectively as possible. The parents should be told to administer the supplement through a straw to prevent staining of the teeth, which can be a side effect of the iron solution. Additionally, while iron absorption can be enhanced by Vitamin C, iron supplements should not be administered with milk or antacids, and ideally not at mealtimes as calcium and certain compounds in food can interfere with absorption. Liquid iron supplements should not be mixed with cereal or added to formula unless specifically directed by a healthcare professional, as this might also interfere with iron absorption.