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evidence · mechanism · dose
Supplements/Mineral

Magnesium Oxide

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

Gut Health

Overview

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

Natural sources
    Common forms

      Forms & variants of Magnesium

      Different chemical forms of Magnesium behave differently. Browse each form's mechanism, bioavailability, and best-use context.

      Parent
      Magnesium

      Essential cofactor in 300+ enzymatic reactions, from ATP production to muscle relaxation.

      Glycinate
      Magnesium Glycinate

      Chelated magnesium bound to glycine — best-tolerated form for sleep, calm, and muscle relaxation.

      Citrate
      Magnesium Citrate

      Highly bioavailable magnesium with a mild osmotic laxative effect — useful for constipation and repletion.

      Malate
      Magnesium Malate

      Magnesium + malic acid — favored for daytime energy and fibromyalgia-related fatigue.

      L-Threonate
      Magnesium L-Threonate

      Magnesium bound to L-threonic acid — the only form shown to meaningfully raise brain magnesium.

      Taurate
      Magnesium Taurate

      Magnesium + taurine — gentle on the gut with cardiovascular and glycemic synergies.

      Chloride
      Magnesium Chloride

      Topical and oral magnesium with good absorption — commonly used in 'magnesium oil' sprays.

      Orotate
      Magnesium Orotate

      Magnesium + orotic acid — studied specifically in heart failure and athletic populations.

      Sulfate (IV)
      Magnesium Sulfate (IV)

      Reference IV form used in eclampsia and acute asthma.

      Acetyl-taurate
      Magnesium Acetyl-Taurate

      Brain-penetrant Mg form combined with taurate for mood.

      Mechanism of action

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

      Pathways
      • · Antacid
      • · Osmotic laxative

      Effects on the body

      Supports
      Acute constipation relief

      Organ system effects

      Evidence-based benefits

      Effective osmotic laxative

      Strong evidence

      Poor for raising serum Mg

      Strong evidence

      Bioavailability ~4%.

      Potential side effects

      Common
      • · Diarrhea
      • · Cramping
      Rare
        Serious
        • · Mg toxicity in renal impairment

        Drug interactions

        No notable interactions reported.

        Supplement interactions

        Pairs well with

        None listed.

        Avoid combining with

        No specific avoidances listed.

        Dosing & bioavailability

        Typical dose
        250–500 mg elemental for laxative effect
        With food?
        With water

        Where to buy

        Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.

        Mineral
        Magnesium Ox…
        Amazon
        Wide selection · fast shipping
        Mineral
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        iHerb
        Global delivery · curated brands
        Mineral
        Magnesium Ox…
        Thorne
        Practitioner-grade · NSF tested

        Scientific evidence (9)

        RCTJ Neurogastroenterol Motil · 2019

        Magnesium oxide for constipation

        Mori H, et al.

        RCT of MgO in chronic constipation.

        Key findings

        Effective stool softener at 1.5 g/d.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: Magnesium Oxide — Effective osmotic laxative

        Live PubMed search

        Live results for "Magnesium Oxide Effective osmotic laxative" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

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

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: Magnesium Oxide — Poor for raising serum Mg

        Live PubMed search

        Live results for "Magnesium Oxide Poor for raising serum Mg" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

        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.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: Magnesium Oxide — randomized controlled trial

        Live PubMed search

        Live results for "Magnesium Oxide randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

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

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: Magnesium Oxide — meta-analysis

        Live PubMed search

        Live results for "Magnesium Oxide meta-analysis" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

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

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: Magnesium Oxide — pharmacokinetics

        Live PubMed search

        Live results for "Magnesium Oxide pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

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

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: Magnesium Oxide — safety adverse events

        Live PubMed search

        Live results for "Magnesium Oxide safety adverse events" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

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

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: Magnesium Oxide — dose response

        Live PubMed search

        Live results for "Magnesium Oxide dose response" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

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

        Open study
        Systematic reviewGoogle Scholar · 1970

        Google Scholar: Magnesium Oxide — clinical evidence

        Live Scholar search

        Cross-database citation index for Magnesium Oxide as it relates to "clinical evidence".

        Key findings

        Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.

        Open study
        Educational use only. This profile is not medical advice. Consult a qualified healthcare professional before starting any supplement, especially if you take prescription medication or have a chronic condition.