Is Magnesium Safe with Levothyroxine?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Separate levothyroxine and magnesium by at least 4 hours per FDA label.
Why this interaction occurs
Magnesium antacids and supplements reduce levothyroxine absorption via gastric pH and binding effects.
Evidence
Evidence level: moderate.
Data source
FDA Levothyroxine Sodium label 2026
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 302,514 reports mentioning Levothyroxine. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Levothyroxine + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Magnesium interactions → · All Levothyroxine interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.