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Levothyroxine and calcium — GPhC CRA MCQ

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ModerateDrug InteractionsLevothyroxine and calciumGPhC CRA

A 60-year-old man taking levothyroxine starts calcium carbonate for osteoporosis prevention. He takes both tablets with breakfast and his TSH has risen. What is the most important interaction to flag?

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

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Correct answer: E — Separate calcium and levothyroxine doses to reduce impaired absorption

Calcium salts can reduce levothyroxine absorption if taken together. Separating administration times can improve thyroid control and may correct a raised TSH caused by impaired absorption. Similar advice applies to iron and some antacids.

Reference: BNF