Supplement Scholar
Mineral

Magnesium Oxide

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Magnesium Oxide. Cheapest magnesium salt — poor absorption (~4%) but useful as a laxative or antacid.

How it works. Poorly absorbed; remaining Mg neutralizes stomach acid and exerts osmotic effect in the colon.

What the research supports. 2 graded claims. Strongest: Effective osmotic laxative (strong).

How much to take. Typical dose: 250–500 mg elemental for laxative effect.

Side effects and interactions. 1 medication interaction listed. Serious: Mg toxicity in renal impairment.

Stacking. Pairs well with A high-quality multivitamin, Omega-3 (EPA/DHA).

Common forms. Available as Chelated form (glycinate, bisglycinate, citrate, malate), Inorganic salt (oxide, sulfate, chloride), Liquid ionic solution, Topical or transdermal preparation.

Key studies. 9 studies cited. The strongest are listed with links to PubMed.

Community. Experiences from people who have tried Magnesium Oxide. Anecdotes are not medical advice.

Magnesium Oxide. Cheapest magnesium salt — poor absorption (~4%) but useful as a laxative or antacid.

Molecular structureMgO · 40.305 g/mol

What it is

Cheapest magnesium salt — poor absorption (~4%) but useful as a laxative or antacid.

Food sources

Whole foods (leafy greens, legumes, nuts, seeds, seafood, animal proteins)Fortified foods such as cereals, breads, plant milks, and table saltMineral supplements as chelates, citrates, glycinates, or inorganic salts

Goals

Gut Health

How it works

Poorly absorbed; remaining Mg neutralizes stomach acid and exerts osmotic effect in the colon.

Pathways

  • Antacid
  • Osmotic laxative

Effects

  • +Acute constipation relief supports

What the research supports

Effective osmotic laxativestrong
Poor for raising serum Mgstrong

Strong: consistent results across large trials or meta-analyses. Moderate: several trials, mostly positive. Limited: small or mixed studies. Preclinical: animal or cell research only.

Typical dose
250–500 mg elemental for laxative effect
TimingConsistent daily timing recommended; split larger doses if GI tolerance is a concern.
With foodWith water
Best formMost evidence is based on the chelated form (glycinate, bisglycinate, citrate, malate) form.
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Side effects & interactions

Common side effects

  • Diarrhea
  • Cramping

Serious

  • Mg toxicity in renal impairment

Medication interactions

Prescription medications (general)minor

Always disclose Magnesium Oxide use to your prescriber — additive, antagonistic, or pharmacokinetic interactions are possible.

Check any supplement–medication combination with your pharmacist before starting.

Combines with

Pairs well

  • A high-quality multivitaminCovers micronutrient cofactors that support most supplement pathways.
  • Omega-3 (EPA/DHA)Foundational anti-inflammatory support that complements most regimens.

Common forms

  • Chelated form (glycinate, bisglycinate, citrate, malate)
  • Inorganic salt (oxide, sulfate, chloride)
  • Liquid ionic solution
  • Topical or transdermal preparation

Key studies

9 studies cited in total.

PubMed: Magnesium Oxide — Effective osmotic laxative ↗
Systematic review · PubMed (NLM) · 2026

Opens current human and preclinical literature matching Magnesium Oxide and "Effective osmotic laxative". Filter by RCT, meta-analysis, or year on the results page.

PubMed: Magnesium Oxide — Poor for raising serum Mg ↗
Systematic review · PubMed (NLM) · 2026

Opens current human and preclinical literature matching Magnesium Oxide and "Poor for raising serum Mg". Filter by RCT, meta-analysis, or year on the results page.

PubMed: Magnesium Oxide — randomized controlled trial ↗
Systematic review · PubMed (NLM) · 2026

Opens current human and preclinical literature matching Magnesium Oxide and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

Discussion

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