Magnesium L-threonate and magnesium glycinate are both chelated magnesium forms, but they are not interchangeable in a formula. The difference that matters at the bench is how much elemental magnesium each gram of powder actually delivers.
Elemental magnesium content
| Form | Approx. elemental Mg | Grams of powder per 100 mg elemental |
| Magnesium L-threonate | ~8.3% | ~1.2 g |
| Magnesium bisglycinate | ~14% | ~0.7 g |
| Magnesium citrate (anhydrous) | ~16% | ~0.6 g |
| Magnesium oxide | ~60% | ~0.17 g |
The figures above are calculated from molecular weight, not measured. Always confirm the declared elemental content on the supplier specification sheet, because hydrate form and residual moisture shift the real number.
What that means for capsule load
A two-capsule serving with a 1000 mg fill can carry roughly 83 mg of elemental magnesium as L-threonate, or about 140 mg as bisglycinate. To reach 300 mg elemental from L-threonate alone you need close to 3.6 g of powder, which does not fit a two-capsule serving. That is why L-threonate products are often dosed at a lower elemental figure per serving, or blended with a second, denser carrier.
Handling and sensory differences
- Solubility. Both dissolve readily, but L-threonate solutions are less likely to leave a chalky mouthfeel at high concentration.
- Taste. Glycinate carries a faint sweetness; L-threonate is closer to neutral, which matters in stick packs and gummies.
- Hygroscopicity. Both pick up moisture. Blending and filling rooms should stay below 45% RH, and the powder should be released from the sealed liner only at the filling station.
- Compaction. L-threonate compacts less readily than glycinate, so direct compression formulas usually need a binder or a roller-compacted granulate.
Choosing between them
The decision is usually driven by three constraints rather than by preference:
- Serving size. If the label claims a high elemental figure in one or two capsules, glycinate or citrate carries it more easily.
- Label positioning. L-threonate is a distinct ingredient and needs its own specification, its own assay method and its own cost line.
- Blend partners. Glycinate blends cleanly with taurate, citrate and malate. L-threonate is usually kept as the single magnesium source so the declared figure stays easy to audit.
What to ask a supplier for
- Assay method, and the elemental magnesium figure derived from it
- Identity of the chelating agent, confirmed by FTIR or NMR, not only by the label
- Heavy metals, microbiological limits and loss on drying, per batch
- Particle size distribution, if the material goes into direct compression
- Statement on hydrate form and on any carrier or anticaking agent present
Both forms, one supply chain
We supply magnesium L-threonate and magnesium glycinate from the same group, with the specification sheet issued before the first order and a COA with each batch. If you are reformulating an existing magnesium SKU and want the elemental figures checked against your current label, send the panel and we will work through the numbers with you.