Final answer:
Calcium and iron supplements can interfere with the effectiveness of levothyroxine, a medication for hypothyroidism, by affecting its absorption. These supplements should be taken several hours apart from levothyroxine.
Step-by-step explanation:
A nurse is providing teaching to a client who has hypothyroidism and is receiving levothyroxine. The nurse should instruct the client that certain supplements can interfere with the effectiveness of the medication. Among the supplements listed, calcium and iron are known to interfere with the absorption of levothyroxine, potentially reducing its efficacy.
It is recommended that these supplements be taken several hours apart from levothyroxine to prevent interaction. Vitamin D and magnesium do not have the same level of interaction with levothyroxine as calcium and iron do.