Can I Take These?

Can You Take Levothyroxine and Magnesium Together?

Magnesium-hydroxide antacid products (not standalone magnesium supplements) can reduce levothyroxine absorption.

MonitorEvidence: Moderate

What the interaction means

Levothyroxine's FDA label names "Antacids - Aluminum & Magnesium Hydroxides" specifically, stating: "Gastric acidity is an essential requirement for adequate absorption of levothyroxine. Sucralfate, antacids and proton pump inhibitors may cause hypochlorhydria, affect intragastric pH, and reduce levothyroxine absorption. Monitor patients appropriately."

Why it may happen

Reduced gastric acidity from magnesium-hydroxide-containing antacids impairs levothyroxine absorption, per the label.

Practical context

This is specifically about magnesium-hydroxide *antacid* products (e.g. Milk of Magnesia-type formulations), not standalone elemental magnesium supplements (oxide, citrate, glycinate -- the typical supplement forms). No specific spacing interval is given for this group (unlike the label's separate calcium carbonate/ferrous sulfate 4-hour instruction); the label's guidance here is to monitor thyroid function.

What the sources say

Levothyroxine Sodium Capsules — FDA Prescribing Information — YARAL Pharma, Inc. (via DailyMed, U.S. National Library of Medicine)

Last reviewed 2026-08-23

Medical information disclaimer: this information is general and educational. It does not diagnose conditions, prescribe treatment, or determine whether a combination is safe for you personally. Follow your prescription label and ask a pharmacist or clinician before starting, stopping, or combining products. Full disclaimer.

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