A bottle marked 1,000mg of magnesium glycinate contains about 140mg of magnesium. Both numbers are true.
Minerals are not sold as pure minerals. Magnesium, zinc and iron are all bound to something else — an acid, an amino acid, a salt — to make them stable and absorbable.
That means every mineral supplement has two weights:
- Compound weight — the whole molecule, mineral plus what it is bound to
- Elemental weight — the mineral itself
Only the elemental weight is the dose. The compound weight is always the larger number, which is why it is usually the one on the front.
The magnesium example
Magnesium glycinate is roughly 14% elemental magnesium by weight. So:
1,000mg of magnesium glycinate contains about 140mg of magnesium.
A label reading "Magnesium Glycinate 1,000mg" is accurate. A shopper comparing it against a product stating "Magnesium 200mg" would reasonably read the first as five times the size. It is actually the smaller dose.
Telling them apart
The Supplement Facts panel is where the answer is, and the wording is precise:
- "Magnesium ... 200mg" — elemental. This is the dose.
- "Magnesium Glycinate ... 1,500mg" — compound weight.
- "Magnesium (as magnesium bisglycinate) ... 200mg" — elemental, with the form named. This is the clearest way to write it.
The %DV column is a useful cross-check. The Daily Value for magnesium is 420mg, so a product showing 48% DV contains about 200mg elemental regardless of what the front of the bottle says.
Glycinate and bisglycinate are the same compound
Worth saying plainly, because we sell both names. Magnesium bisglycinate is magnesium bound to two glycine molecules — the "bis" names the two. "Magnesium glycinate" is the everyday name for the same thing. A product using one name is not carrying a different active ingredient from a product using the other.
Where they genuinely differ is format and what else is in the tub, not chemistry.
Why the forms differ
Different magnesium compounds do carry different proportions of elemental magnesium, and they are not interchangeable:
| Form | Roughly elemental |
|---|---|
| Magnesium oxide | ~60% |
| Magnesium citrate | ~16% |
| Magnesium glycinate / bisglycinate | ~14% |
| Magnesium L-threonate | ~8% |
Oxide looks best on that table and is among the least well absorbed of the common forms — a high elemental percentage does not mean a high absorbed amount. This is exactly why one number in isolation is not enough.
What we do
Both of our magnesium products state 200mg of elemental magnesium per serving, drawn from 1,500mg of magnesium glycinate, with the compound weight shown so you can see where the number comes from. One is a capsule, one is a flavored powder. Same compound, same elemental dose, different format.
If you want the rest of the panel decoded, read how to read a label.