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Levothyroxine and iron — GPhC CRA MCQ

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ModerateDrug InteractionsLevothyroxine and ironGPhC CRA

A 57-year-old woman taking levothyroxine 100 micrograms daily buys ferrous sulfate after being told she is anaemic. She takes levothyroxine with breakfast and plans to take iron at the same time. What would you advise the patient?

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

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Correct answer: A — Separate iron and levothyroxine dosing because iron can reduce levothyroxine absorption

Iron salts can bind levothyroxine in the gut and reduce absorption, leading to poor thyroid control. The medicines should be separated by an appropriate interval and levothyroxine should be taken consistently. Milk and calcium can also reduce levothyroxine absorption. Stopping thyroid treatment or taking iron weekly would be unsafe or ineffective.

Reference: BNF