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Levothyroxine and iron — GPhC CRA MCQ

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ModerateEndocrine TherapeuticsLevothyroxine and ironGPhC CRA

A 24-year-old woman taking levothyroxine 100micrograms each morning buys ferrous sulfate for iron deficiency. She usually takes all medicines with breakfast before work. Her recent TSH was above range. What would you advise the patient?

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Correct answer: D — Separate ferrous sulfate and levothyroxine by several hours

Iron salts can reduce levothyroxine absorption and contribute to poor thyroid control. The raised TSH and current dosing habit make this interaction relevant. Separating administration times and taking levothyroxine consistently supports stable thyroid replacement.

Reference: BNF; NICE CKS