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Magnesium × Levothyroxine

MODERATE INTERACTION — Possible Evidence

⚠️ Mechanism

Magnesium may reduce levothyroxine absorption, similar to calcium.

📋 Effect

Reduced levothyroxine absorption; hypothyroid symptoms

💊 Management

Separate doses by at least 4 hours.

Plain Language Summary

This combination requires caution because magnesium can prevent your body from absorbing levothyroxine properly. This may lead to symptoms of an underactive thyroid if the doses are taken too close together.

Source

Singh N et al. JAMA 2000 (extrapolated from calcium data)

Supporting Research

The association between circulating magnesium and clinically relevant outcomes in patients with chronic kidney disease: A systematic review and meta-analysis PMID:33419615 DOI:10.1016/j.clnu.2020.12.015 2021
Interventions for preventing post-operative atrial fibrillation in patients undergoing heart surgery PMID:23440790 DOI:10.1002/14651858.CD003611.pub3 2013
Association between Serum Magnesium and Fractures: A Systematic Review and Meta-Analysis of Observational Studies PMID:36986033 DOI:10.3390/nu15061304 2023
A meta-analysis of methane-mitigation potential of feed additives evaluated in vitro PMID:38353472 DOI:10.1016/S0022-0302(23)00819-6 2024
Dietary Approaches to Stop Hypertension (DASH) for the primary and secondary prevention of cardiovascular diseases PMID:40326569 DOI:10.1002/14651858.CD013729.pub2 2025
Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies PMID:23719551 DOI:10.3945/ajcn.112.053132 2013
Inhaled magnesium sulfate in the treatment of acute asthma PMID:29182799 DOI:10.1002/14651858.CD003898.pub6 2017
Pharmacological interventions for benzodiazepine discontinuation in chronic benzodiazepine users PMID:29543325 DOI:10.1002/14651858.CD011481.pub2 2018
Medical Disclaimer: This interaction record is for informational and educational purposes only and does not constitute medical advice. Drug-supplement interactions can be dangerous. Always consult your healthcare provider or pharmacist before combining any supplement with prescription medications. Do not stop or change any medication without professional guidance.