Magnesium oxide has the HIGHEST elemental magnesium per weight (60%) but the LOWEST bioavailability (~4%). Most passes through unabsorbed — acting as an osmotic laxative. Useful FOR constipation (Milk of Magnesia). NOT useful for correcting magnesium deficiency. The cheapest form, which is why it's in most 'magnesium' products. If a label says 'magnesium' without specifying the form, it's almost always oxide. Our assessment: laxative, not a supplement. --- *Reviewed by the Dose AI Research Team and Clinical Advisory Board* *Last updated: 2026-04-06*
Based on independent third-party laboratory analysis
Category pass rate: ~80% of magnesium products passed independent laboratory testing. However, form accuracy is a MAJOR issue — some brands label one form but contain a different (cheaper) form.
Contamination risk: Low risk category. Heavy metals rarely an issue in mineral supplements at tested doses.
Reviewed by the Scan Dose Research Team and Clinical Advisory Board | Last updated:
Not medical advice. Based on published clinical research and systematic reviews.