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Warfarin and thyroid status — GPhC CRA MCQ

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HardEndocrine TherapeuticsWarfarin and thyroid statusGPhC CRA

A patient stabilised on warfarin starts levothyroxine after newly diagnosed hypothyroidism. The GP asks whether anticoagulation monitoring needs changing. What is the most important interaction to flag?

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Correct answer: C — INR may change as thyroid status is corrected

Changes in thyroid status can alter warfarin sensitivity. INR should be monitored when levothyroxine is started or thyroid function changes. In this scenario, the correct option is iNR may change as thyroid status is corrected. The other options are plausible but do not address the key clinical, legal or safety issue as directly. This aligns with UK pharmacy practice guidance cited in the reference field.

Reference: BNF; Stockley's Drug Interactions