Drug interactions
Levothyroxine + Magnesium supplement
Severity: Moderate
Levothyroxine and Magnesium supplement: 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
Oral magnesium can bind levothyroxine in the gut and reduce its absorption. This may raise TSH and cause loss of thyroid control if the two are taken together regularly.
What this interaction means in plain words
Levothyroxine and Magnesium supplement 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
Magnesium binds or adsorbs levothyroxine in the gastrointestinal tract, decreasing absorption.
What to do
Take levothyroxine at least 4 hours apart from magnesium supplements. Monitor TSH if the supplement is started or stopped.
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 Levothyroxine with Magnesium supplement?
MediHelp rates the interaction as moderate. Levothyroxine and Magnesium supplement 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. Oral magnesium can bind levothyroxine in the gut and reduce its absorption. This may raise TSH and cause loss of thyroid control if the two are taken together regularly.
How serious is the interaction between Levothyroxine and Magnesium supplement?
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 apart from magnesium supplements. Monitor TSH if the supplement is started or stopped.
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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