Magnesium
Essential mineral involved in 300+ enzymatic reactions. FDA RDI for adults 4+ is 420 mg per day. Common forms include glycinate, citrate, and oxide.
FDA Reference Data
About Magnesium
Magnesium is a mandatory-declaration mineral when present in supplement products. FDA RDI is 420 mg/day for adults 4+. Different salt forms have varying bioavailability and elemental magnesium content: Magnesium Glycinate is ~14.1% elemental Mg by weight; Magnesium Citrate is ~11.2%; Magnesium Oxide is ~60.3% (but poorly absorbed). On Supplement Facts labels, the declared amount must be elemental magnesium (not the salt weight), per 21 CFR 101.36(b)(2)(ii).
Common Supplement Forms
Note: When a salt form is used, the Supplement Facts panel must declare the elemental amount (e.g., “Magnesium 141 mg 34%”), not the salt weight. The salt name appears in the ingredient list below the panel. See %DV calculator for calculation details.
Frequently Asked Questions
What is the FDA RDI for magnesium?
The FDA RDI for magnesium is 420 mg per day for adults and children 4 years and older (21 CFR 101.9(c)(8)(iv)). This value is based on the National Academies Recommended Dietary Allowance (RDA). The %DV on Supplement Facts labels is calculated as: (declared elemental magnesium / 420) × 100, rounded to the nearest whole percent.
Do I declare the salt weight or elemental magnesium on my Supplement Facts label?
FDA 21 CFR 101.36(b)(2)(ii) requires declaration of elemental magnesium, not the salt weight. For example, if your formula contains 1000 mg of Magnesium Glycinate (~14.1% elemental Mg), the Supplement Facts panel should declare "Magnesium 141 mg 34%" — not "Magnesium Glycinate 1000 mg". The salt form may appear in the ingredient list separately.
Which magnesium form has the highest bioavailability?
Magnesium Glycinate and Magnesium Citrate have the highest documented bioavailability. Magnesium Oxide has high elemental content (~60%) but very poor absorption (~4% bioavailable). For supplement formulations targeting efficacy, glycinate or citrate forms are typically preferred despite their lower elemental percentage per milligram of salt.
How does ReguSift handle magnesium salt-to-element conversion?
ReguSift automatically converts magnesium salt weights to elemental magnesium values using built-in conversion factors (e.g., 1000 mg Magnesium Glycinate → 141 mg elemental Mg). This conversion is applied once in the pipeline to prevent exponential factor application. The declared amount on the Supplement Facts panel reflects elemental magnesium, and %DV is calculated against the 420 mg RDI.
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Building a supplement with Magnesium?
ReguSift extracts ingredients from your COA, calculates %DV, formats proprietary blends, and generates a print-ready Supplement Facts label — including Magnesium auto-formatted per FDA 21 CFR 101.36.