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Levothyroxine and ferrous sulfate — GPhC CRA MCQ

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ModerateDrug InteractionsLevothyroxine and ferrous sulfateGPhC CRA

A patient takes levothyroxine at breakfast and starts ferrous sulfate; TSH has risen despite adherence. What is the most important interaction to flag?

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Correct answer: A — Iron can reduce levothyroxine absorption

Ferrous sulfate can bind levothyroxine and reduce its absorption if taken close together. This makes iron can reduce levothyroxine absorption the single best answer in this scenario. The other options would either miss the key safety issue, delay appropriate review, or fail to meet the relevant clinical or professional requirement.

Reference: BNF interactions