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Levothyroxine and iron — GPhC CRA MCQ

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ModerateDrug InteractionsLevothyroxine and ironGPhC CRA

A patient taking levothyroxine every morning has been started on ferrous sulfate for iron deficiency anaemia. She plans to take both tablets together before breakfast. What is the most important interaction to flag?

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Correct answer: D — Iron can reduce levothyroxine absorption

Iron salts can bind levothyroxine in the gut and reduce its absorption. The medicines should be separated by a suitable interval to maintain thyroid control. Reduced levothyroxine absorption may lead to hypothyroid symptoms or altered thyroid tests. The interaction is not a conversion or direct effect on haemoglobin synthesis.

Reference: BNF