Mineral
Magnesium Oxide
Also known as: MgO, Milk of magnesia
High elemental magnesium content but poor absorption (4%). Primarily useful as a laxative; not ideal for Mg repletion.
Primary uses
- Laxative
- Basic magnesium supplementation
- Constipation
- Strong laxative effect
How it works
- Only 4% absorbed
- Strong osmotic laxative effect
- High elemental content per weight
Dosage
- Typical range
- 400-500 mg (only ~20mg absorbed)
- Timing
- Any
- With food
- Optional
- Duration
- Better forms available
- Special populations
- Primarily as laxative
Forms
- Tablet
- Capsule
- Tablets
- Liquid (milk of magnesia)
- Capsules
Safety
Common side effects
- Diarrhea common
Contraindications
- Kidney disease
Known interactions
- Cautionwith calcium
High calcium can impair magnesium absorption
- Infowith magnesium
High-dose magnesium may slightly reduce zinc absorption
- Synergywith magnesium
Magnesium needed for vitamin D activation
- Synergywith melatonin
Complementary sleep support
- Synergywith glycine
Both support sleep through different mechanisms
- Cautionwith magnesium
Magnesium may enhance BP lowering effect
Evidence notes
Well-established laxative effect
Grade A: Multiple well-designed human trials support the main claims.
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Open the checkerMedical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider.