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Levothyroxine and iron — GPhC CRA MCQ

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ModerateEndocrine TherapeuticsLevothyroxine and ironGPhC CRA

A 51-year-old woman taking levothyroxine 100 micrograms each morning has started ferrous sulfate for iron deficiency anaemia. She says her fatigue has worsened and TSH has risen since starting iron. She takes both medicines together with breakfast. What would you advise the patient?

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Correct answer: A — separate levothyroxine and iron dosing by several hours and recheck thyroid function as planned

Iron salts reduce levothyroxine absorption and can lead to loss of thyroid control. Separating administration times and taking levothyroxine consistently on an empty stomach can improve absorption. Thyroid function should be rechecked after a stable dosing pattern. Dose changes should be made by the prescriber based on TSH response.

Reference: BNF; NICE CKS: Hypothyroidism