Can you take Magnesium with Thyroid hormones?
This is general information, not medical advice. Supplements can interact with medicines and health conditions. Always check with your doctor or pharmacist before starting or changing supplements.
What the evidence says
Magnesium is a polyvalent cation, and levothyroxine can bind to polyvalent cations in the gut, forming a complex that your body absorbs poorly, which can lower the medication's effectiveness. A 2025 randomised crossover trial in healthy adults tested this directly: taking magnesium aspartate together with a levothyroxine dose significantly reduced how much levothyroxine reached the bloodstream (AUC reduced by 12%, with peak level also reduced and delayed); magnesium citrate showed a smaller, seven percent reduction that did not reach statistical significance in this study. Because the effect was clearest with one magnesium form and only a non-significant trend with another, and because the trial was small (15 healthy subjects, not people with hypothyroidism), it's reasonable to treat any magnesium supplement as a candidate for the same interaction rather than assume citrate is exempt. If you take levothyroxine, take your magnesium supplement at least 4 hours before or after your dose, and mention any new magnesium supplement to your doctor if your thyroid levels have been stable.
Keep at least 4 hours between them.
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We check against a limited set of medications. Absence of a warning here is not evidence of safety. Always confirm with your pharmacist.