Drug interactions
Calcium citrate + Levothyroxine
Severity: Moderate
Calcium citrate and Levothyroxine: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Calcium citrate taken close to levothyroxine can reduce its absorption, leading to elevated TSH and loss of thyroid control. This has been described for calcium supplements generally.
What this interaction means in plain words
Calcium citrate and Levothyroxine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Calcium forms insoluble complexes with levothyroxine in the gastrointestinal tract, reducing absorption.
What to do
Take levothyroxine at least 4 hours before or after calcium citrate. Recheck TSH 6 to 8 weeks after changes.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Levothyroxine
Frequently asked questions
Can I take Calcium citrate with Levothyroxine?
MediHelp rates the interaction as moderate. Calcium citrate and Levothyroxine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Calcium citrate taken close to levothyroxine can reduce its absorption, leading to elevated TSH and loss of thyroid control. This has been described for calcium supplements generally.
How serious is the interaction between Calcium citrate and Levothyroxine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Take levothyroxine at least 4 hours before or after calcium citrate. Recheck TSH 6 to 8 weeks after changes.
What other medicines interact with Levothyroxine?
MediHelp also lists interactions of Levothyroxine with, for example, Cholestyramine, Sodium iodide i-131, Tiratricol. The full list is on the Levothyroxine page.
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