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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 and is prescribed ferrous sulfate. What is the most important interaction to flag?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: AReduced levothyroxine absorption

Iron salts can reduce levothyroxine absorption and doses should be separated. In this vignette, "Reduced levothyroxine absorption" is the safest single best answer. The other options are less appropriate because they miss the key clinical risk, conflict with UK medicines guidance, or delay needed review.

Reference: BNF