Each participant received three treatment conditions
Fifteen healthy adults received levothyroxine alone, with magnesium aspartate, and with magnesium citrate in a randomized crossover study. The magnesium preparations were powders, and the investigators measured thyroxine exposure over six hours. [1]
Exposure was 12% lower with aspartate. The 7% lower estimate with citrate was not statistically significant. Neither comparison directly measured long-term thyroid symptoms or dose requirements in people with hypothyroidism. [1]
Review the exact preparation and schedule
The findings do not prove that every magnesium tablet has the same effect as the tested powders. They also do not establish the best separation interval; the study compared simultaneous administration with levothyroxine alone. [1]
Ask the prescribing clinician or pharmacist how to arrange the specific products, particularly when stable thyroid results are important. Do not compensate by changing a levothyroxine dose independently. The authors reported no conflicts and no specific funding. [1]
An absorption result is not a dosing instruction
Imagine an interaction study reports lower hormone exposure. That is a reason to review administration, not a calculation telling someone to increase their prescription by the same percentage.
| Detail | Interpretation |
|---|---|
| 15 healthy adults | Limited population |
| Six-hour exposure | Pharmacokinetic endpoint |
| Long-term thyroid control | Not directly tested |
Sources for this article
- Single Center, Open‐Label, Randomized Crossover Trial on Drug–Drug Interactions of Levothyroxine/Magnesium‐Citrate and Levothyroxine/Magnesium‐Aspartate in Healthy Subjects—The ThyroMag Trial - PMC
Source consulted: 2026-09-19. This is a reference resource, not a claim that we conducted the studies or tested a product.