Moderate interactionModerateSeparate by 4h
Magnesium oxide and Levothyroxine: interaction, severity and spacing
Magnesium oxide and Levothyroxine interact because magnesium salts bind levothyroxine and reduce its absorption when taken at the same time. Take them 4 hours apart. Moderate risk.
Last reviewed: 2026-09-20Reviewed by: StackingRight clinical review
The interaction in detail
| Pair | Magnesium oxide and Levothyroxine |
|---|---|
| Type | Nutrient–drug interaction |
| Severity | Moderate |
| Required spacing | 4 hours minimum |
| Onset | At the time of dosing |
Mechanism
Magnesium salts bind levothyroxine and reduce its absorption when taken at the same time.
What to do
Leave at least 4 hours between levothyroxine and magnesium.
How to fit both into one day
Levothyroxine
morningempty stomach
Levothyroxine needs an empty stomach and gastric acid for full absorption. Take it 30-60 minutes before breakfast with plain water, and keep calcium, iron and coffee at least 4 hours away.
Putting Magnesium oxide in the morning and Levothyroxine in the morning satisfies the 4-hour separation without disrupting either one's absorption window.