Elemental Magnesium: How to Read the Number on the Label
Elemental magnesium is the mineral itself, as distinct from the weight of the compound carrying it. A label reading “magnesium glycinate 1,000 mg” describes compound weight; “magnesium (as glycinate) 200 mg” describes elemental. The %DV column is calculated on the elemental figure, so it works as a cross-check.
The single most useful skill in this category is telling the difference between the weight of a magnesium compound and the weight of the magnesium inside it. Labels are not consistent about which they show, and the gap between the two can be large.
Two numbers, one bottle
A supplement facts panel may show any of the following:
- Magnesium (as magnesium glycinate) 100 mg — the clearest format. The 100 mg is elemental magnesium; the bracket tells you the source compound.
- Magnesium glycinate 1,000 mg — the weight of the compound. The elemental magnesium is a fraction of this, and the panel is not telling you what fraction.
- Magnesium bisglycinate 1,000 mg (providing 200 mg elemental magnesium) — both, which is what you want.
The %DV shortcut
Where a panel shows a percentage of Daily Value for magnesium, that percentage is calculated on elemental magnesium. It is therefore a reliable cross-check: if a product claims 1,000 mg but shows a modest %DV, the large number is compound weight.
Serving size, again
Every figure on the panel describes one serving, and the serving is stated at the top — frequently as two or three capsules. A product listing 200 mg elemental magnesium per serving of three capsules delivers roughly 67 mg per capsule. Two products can look identical on the shelf and differ threefold in what a single capsule contains.
A worked comparison
Product A: serving size 2 capsules, magnesium (as bisglycinate) 200 mg, 120 capsules. That is 60 servings at 200 mg elemental.
Product B: serving size 1 tablet, magnesium oxide 500 mg, 100 tablets. The panel shows no elemental figure, but the %DV indicates a substantially higher elemental content than the compound weight alone would suggest for a chelated form. That is 100 servings — but of a different form, at a different elemental dose.
Neither is “better” from these numbers alone. The point is that you cannot compare them until both are expressed as elemental magnesium per serving, and cost is calculated per serving rather than per bottle.
Next
See types of magnesium for what each compound is, and our magnesium comparison to filter products by form and strength.
References
- NIH Office of Dietary Supplements — Magnesium (Health Professional Fact Sheet)
- U.S. FDA — Daily Value on the Nutrition and Supplement Facts Labels