In short
Magnesium is one mineral sold as a dozen products, and the difference is the carrier it is bound to. The carrier changes three things: how much elemental magnesium you get, how well it absorbs, and how the gut tolerates it. Bisglycinate is the evening choice, easy on the system, with a 2025 randomised trial behind the sleep use. Malate suits the day. Citrate absorbs well but moves the bowels. Oxide is cheap and poorly absorbed. Threonate has the best story and the thinnest human evidence. Ranked by evidence for a purpose, not by hype.
Every magnesium bottle contains the same ion. Everything that differs, absorption, tolerance, and the job it suits, comes from what the ion is bound to.
01Why the form matters
Two numbers decide a magnesium product: elemental content and absorption. The carrier dilutes the mineral, which is why 1300 mg of magnesium bisglycinate delivers 156 mg of elemental magnesium, and it gates uptake: in comparative studies, organic salts like citrate absorb meaningfully better than magnesium oxide, whose bioavailability is among the lowest measured.12 The carrier also decides tolerance, because unabsorbed magnesium stays in the gut and pulls water with it. That is the entire physiology of the category, and it sorts the forms cleanly by purpose.
02The forms, side by side
| Form | Absorption | Gut tolerance | Best suited to | Evidence for that use |
|---|---|---|---|---|
| Bisglycinate | Good | Easiest | Evening, sleep support | Direct 2025 RCT |
| Malate | Good | Good | Daytime repletion | Moderate: absorption data, authorised claims |
| Citrate | Good | Laxative at dose | Repletion where bowels tolerate it | Moderate: comparative absorption trials |
| Threonate | Good | Good | Marketed for the brain | Limited: strong animal story, thin human data |
| Oxide | Poor | Laxative | Low cost, occasional use | Limited for repletion; established as laxative |
03For evening and sleep
The evening job wants absorption without stimulation of the gut, which is bisglycinate's case: magnesium bound to glycine, absorbed well, and easy on the digestive system at larger doses. It now has a direct test in its own lane: a 2025 randomised placebo controlled trial of magnesium bisglycinate in adults with poor sleep found improvements in self reported sleep measures.3 One trial is one trial, and it is the right form tested the right way, which is more than most of the category can say.
04For daytime and energy metabolism
The daytime job is repletion behind the authorised claims magnesium actually holds in the EU: normal energy yielding metabolism, normal muscle function, normal nervous system function, and the reduction of tiredness and fatigue.4 Malate serves it well: solid absorption, good tolerance, and a carrier that belongs to the body's own energy cycle. The claims belong to the magnesium, not the carrier, and this page will not pretend otherwise; the carrier's job is to deliver the mineral without cost.
05The threonate question
Magnesium L-threonate carries the category's best story: engineered to raise brain magnesium, with striking results in animal models. The human record is thinner: a 2024 randomised trial in adults with self assessed sleep problems reported improvements in sleep quality and daytime functioning, and the cognitive claims still rest largely on the animal work.5 Limited grade, honestly held: promising, premium priced, and not yet the human evidence base its marketing implies. It is not in this formulation because the evening job already has a directly tested form at a full dose.
06The marketing corrections
The honest corrections
Three corrections the category needs. Chelated is chemistry, not magic: it describes the bond, and bisglycinate's advantage is measured tolerance and absorption, not the word. Milligrams on the front of a label are usually the compound, not the mineral: always read the elemental number, which is why this formulation states both. And no form of magnesium is a sedative; the evening use is support for normal function, within the authorised claims, not a knockout drop.
In the system
The formulation runs the two-form conclusion of this page: malate in the daytime layer, 80 mg elemental, and bisglycinate in the evening layer, 156 mg elemental. The full reasoning is in the forms of magnesium. Build your protocol →
Sources
Next in this thread
The forms of magnesiumThe two forms this system chose, and the jobs they were chosen for.→How we handle evidence. This comparison ranks forms by evidence for a purpose, grades threonate's gap between story and data, and corrects the category's labelling habits. Educational content, not medical advice.