Magnesium
Involved in over 300 processes in the body. Most people quietly don't get enough.
Magnesium is a cofactor for hundreds of enzymes, including those involved in energy production, muscle function, and the regulation of blood pressure. The form matters considerably: magnesium oxide is cheap and widely used but absorbed poorly; glycinate and malate are gentler on digestion and better retained. Sleep quality and muscle recovery are the areas where people most often notice a difference after a few weeks of supplementing. Low dietary intake is common because modern food processing strips magnesium from grains and vegetables.
Reference values
Daily reference values from official nutrition authorities. These are population reference figures, not personal recommendations.
| RDA | Upper limit | Source |
|---|---|---|
| 270 mg | 350 mg | UK SACN DRVs (1991). UL: UK EVM's own supplement-only guidance is 400mg/day, but NIH ODS's 350mg/day supplement-only UL is used here instead — the lower, more conservative figure, consistent with the niacin fix's reasoning (flags supplemental magnesium intake sooner). Neither figure applies to dietary magnesium, which has no established UL. |
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| magnesium oxide | Lower | With food | Either | Strong |
| magnesium malate | Typical | Either | Either | Informational |
| magnesium citrate | Typical | With food | Either | Likely |
| magnesium l-threonate | Higher | Either | Evening | Possible |
| magnesium glycinate (bisglycinate) | Higher | Either | Evening | Strong |
How it pairs with other supplements
Works well with
Magnesium is required as a cofactor for the enzymes that activate vitamin D in the liver and kidney. Low magnesium status can blunt vitamin D effectiveness.
Magnesium is a cofactor for pyridoxal kinase, required to convert pyridoxine to its active coenzyme form PLP. Adequate magnesium status supports full B6 activation.
Taurine supports magnesium retention; combined benefit for cardiovascular function and blood pressure.
Both promote sleep quality through distinct mechanisms (glycine: NMDA-mediated thermoregulation; magnesium: GABA modulation).
Things to watch for
High-dose calcium supplementation (>500 mg per dose) modestly reduces magnesium absorption. Space by 2+ hours when both are taken as standalone supplements at supplement-tier doses.
Stack Almanac tracks which magnesium form you are taking and cross-checks your total intake against SACN reference values, including when you are getting it from multiple sources such as a multivitamin and a standalone supplement.
Track your Magnesium in Stack Almanac
Last reviewed: 2026-05-21. Reference values are adult-general RDAs from UK. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.