A 2,000 mg serving of magnesium L‑threonate prints an elemental magnesium figure in the low hundreds of milligrams. Often around 144 mg.
People read that and assume a misprint. It is not one. It is the lowest magnesium fraction of any form in common use, and it is the beginning of the comparison rather than an objection to it.
What is the difference between magnesium threonate and magnesium glycinate?
Different partners, different fractions. L‑threonate is magnesium bound to threonic acid, a sugar-acid derivative. Glycinate is magnesium chelated to two glycine molecules. Threonate carries about 8% magnesium by weight. A bisglycinate carries about 14%. So a gram of threonate delivers a little over half what a gram of glycinate does.
That fraction is fixed by formula weight rather than by branding, and it is the reason threonate labels print serving sizes in the thousands of milligrams. The compound is large and the magnesium inside it is not.
How much magnesium is in each form?
Divide the elemental figure on the panel by the compound weight. The result is the fraction, and every form has a ceiling it cannot exceed. A finished capsule normally lands under its ceiling because of bound water and excipients, so a product landing above one is the thing worth catching.
| Form | Magnesium by weight |
|---|---|
| Magnesium oxide | about 60% |
| Magnesium citrate | about 16% |
| Magnesium malate | about 15% |
| Magnesium bisglycinate | about 14% |
| Magnesium L‑threonate | about 8% |
These are formula-weight fractions — arithmetic on the compound, not results from a laboratory. Run them forward: 2,000 mg of threonate is around 144 to 160 mg of elemental magnesium, and 2,500 mg of glycinate is around 275 mg. The larger printed number is the smaller dose.
What is threonate actually sold on?
Not the fraction, which is its worst number. It is sold on a property claimed for the compound specifically — that this partner carries magnesium somewhere other forms do not. That is a mechanism claim about a molecule, and it is the entire premium. Strip it out and a buyer is paying several times the price for half the magnesium.
We do not carry the form and we are not going to argue either side of a literature we do not sell on. What we will do is put the fraction next to the price, because that half of the decision is arithmetic and it is available to anyone holding the bottle.
Which form makes sense for a nightly dose?
For a dose taken every night for a year, the deciding variables are tolerance, the elemental figure and the price per milligram of magnesium. A chelated form such as glycinate wins the last two by a wide margin. Threonate is a defensible purchase only if its specific claim is the thing being bought.
Night Work is 275 mg of elemental magnesium from 2,500 mg of magnesium glycinate, three capsules, one form. 275 ÷ 2,500 is 11%, under the roughly 14% ceiling for a bisglycinate. No second form, no blend, and nothing in the capsule whose quantity is not printed.
What the research does not show
The form-specific literature is younger and thinner than the literature it is compared against. Magnesium’s established physiological roles rest on decades of work. The claims particular to one partner molecule rest on much less, and the gap between those two bodies of evidence is not visible on a bottle.
Cross-form absorption comparisons do not support decimal-point precision. The studies are small, use different methods and different endpoints, and disagree with each other. The direction of the chelated-versus-inorganic comparison is reasonably consistent. Nothing beyond a direction is supportable.
What we will stand on is magnesium’s established roles — normal muscle function, normal nervous-system function, normal energy metabolism.* Those are the honest basis for taking it, and they belong to the mineral rather than to any one partner molecule.
More in this cluster: bisglycinate against glycinate, and the buffered blend, glycinate against oxide, and the 350 mg supplemental ceiling. Night Work’s measured figures are on Testing & Certification.