Magnesium bound to L-threonic acid, a vitamin C metabolite, developed specifically on the claim that it raises magnesium concentrations in the brain more effectively than other salts. It supplies only about 8% elemental magnesium.
Magnesium threonate is the most expensive magnesium on the shelf and the one with the least human evidence supporting its distinguishing claim. The brain-magnesium finding comes from rodent work by the group that developed and patented the compound. Human trials number in the low single digits: a small study in adults with cognitive impairment and a handful of short studies on sleep and cognition, several funded by the ingredient supplier, none independently replicated, none measuring brain magnesium in people. It also supplies less elemental magnesium per capsule than any other common form, so as a way of correcting magnesium intake it is poor value on its own terms.
Sold as
Capsule, Powder, Branded Magtein, Component of nootropic blends
Standardised to
Usually sold as a branded ingredient with a stated elemental magnesium content around 8% — a product without this marker may not resemble what was studied.
Regulation: Subject to the same 350 mg/day supplemental magnesium upper limit as other forms. Sold as a dietary supplement with no pre-market efficacy review; the brain-penetration claim has never been assessed by a regulator.
What the research used
The amounts, forms and durations published trials of Magnesium L-threonate actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Roughly 144 mg of elemental magnesium. From a small trial in adults with cognitive impairment, funded by the ingredient developer, with high dropout and no independent replication.
Studied for Typical retail supplement
1000–2000 mg
Not enough
Salt weight, daily
The elemental magnesium figure — usually 72–144 mg — is the one that matters for magnesium status, and is often far smaller than the number printed largest on the bottle.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
🌙Evening
Not enough
Commonly dosed in the evening or split between afternoon and bedtime, following the trial protocols. No timing comparison has been made.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
The evidence in depth
Best supported: Limited
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
A small trial in adults with cognitive complaints reported improvement on composite cognitive measures. It was funded by the compound's developer, had substantial dropout, and has not been independently replicated. The brain-magnesium mechanism has only been demonstrated in rodents.
What may be going on: Rodent work reported that this salt raises cerebrospinal fluid magnesium and increases synaptic density in the hippocampus. Neither has been shown in humans.
Limited evidence. Early human work, or mostly lab and animal research.
There is not enough evidence that magnesium threonate improves sleep. The few short studies reporting sleep benefits are small, supplier-supported and use subjective questionnaires.
Not enough evidence. Not enough human research to say anything useful yet.
No source is attached to this association yet, so it is rated not enough evidenceby default. It is listed because people commonly ask about it — not because there is evidence for it.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Too much
Kidney impairment
As with every magnesium salt, impaired kidney function allows magnesium to accumulate, with potentially serious cardiovascular and neuromuscular effects.
Worth knowing
Very low elemental magnesium for the price
At roughly 8% elemental magnesium and several times the cost of citrate, this is the least efficient way to raise magnesium intake. Anyone buying it for magnesium status specifically is paying a large premium for a small amount.
Worth knowing
The distinguishing claim rests on rodent data
Brain magnesium elevation, synaptic density and memory improvement were demonstrated in rats. The human evidence does not test the mechanism at all, and the trials that exist come from parties with a commercial interest.
Interaction
Same medicine interactions as other magnesium salts