Magnesium and thyroid function: what's the link?
Magnesium is required for the conversion of T4 to active T3 and for normal TSH signalling. Some studies show lower thyroid antibodies with adequate magnesium intake. If you take levothyroxine, separate it from magnesium by at least 4 hours.
Last updated 27 June 2026
The thyroid-magnesium connection
Selenium, zinc, iron, and magnesium are all required for healthy thyroid hormone synthesis and conversion. Magnesium deficiency is more common in people with hypothyroidism and Hashimoto's.
Dosing with levothyroxine
Levothyroxine must be taken on an empty stomach. Magnesium can reduce its absorption if taken too close. Standard advice: levothyroxine 30–60 min before breakfast, magnesium with dinner or at bedtime.
Frequently asked
- Will magnesium affect my TSH?
- Indirectly, by supporting normal thyroid function — but it does not replace medication.
- Best form for thyroid?
- Glycinate is best tolerated alongside other supplements.
Educational content — not medical advice. Health claims comply with EU Regulation 1924/2006 and the Union Register of authorised claims (Regulation 432/2012). Food supplements are not a substitute for a varied, balanced diet and a healthy lifestyle. Always consult your GP or pharmacist before changing supplements, particularly if you take prescription medication or have kidney disease.