Drug interactions
Calcium + Levothyroxine
Severity: Moderate
Calcium 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 supplements, especially calcium carbonate, reduce oral levothyroxine absorption and can raise TSH in hypothyroid patients. The effect may be missed unless thyroid function is checked.
What this interaction means in plain words
Calcium 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 belongs to Gastrointestinal Tract; Levothyroxine belongs to Endocrine.
Why it happens
Calcium binds levothyroxine in the gut, forming insoluble complexes that impair absorption.
What to do
Separate levothyroxine and calcium by at least 4 hours and monitor TSH after starting or changing calcium therapy.
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 Calcium
- Calcium + Ceftriaxone Contraindicated
- Acalabrutinib + Calcium Moderate
- Alendronate + Calcium Moderate
- Atazanavir + Calcium Moderate
- Baloxavir marboxil + Calcium Moderate
- Bendroflumethiazide + Calcium Moderate
Other interactions of Levothyroxine
Frequently asked questions
Can I take Calcium with Levothyroxine?
MediHelp rates the interaction as moderate. Calcium 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 supplements, especially calcium carbonate, reduce oral levothyroxine absorption and can raise TSH in hypothyroid patients. The effect may be missed unless thyroid function is checked.
How serious is the interaction between Calcium 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: Separate levothyroxine and calcium by at least 4 hours and monitor TSH after starting or changing calcium therapy.
What other medicines interact with Calcium?
MediHelp also lists interactions of Calcium with, for example, Ceftriaxone, Acalabrutinib, Alendronate. The full list is on the Calcium page.
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