Verdict, decision matrix, deep dives, sourcing notes & full sources

Magnesium L-Threonate (Magtein)

The only magnesium salt with credible evidence for raising brain (CSF) magnesium beyond what oral Mg from other forms achieves. | Compound

Aliases (5)

Mg L-threonate · Magtein · MgT · Magnesium threonate · L-Threonic acid magnesium salt

TYPICAL DOSE

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▸ Overview TL;DR

The only magnesium salt with credible evidence for raising brain (CSF) magnesium beyond what oral Mg from other forms achieves. Developed at MIT (Liu / Slutsky / Tonegawa 2010) and clinically licensed as Magtein. One B-tier human RCT (Liu 2016) shows cognitive improvement in older adults with subjective memory complaints over 12 weeks at 1.5-2 g/day Magtein. For Dylan: confirmed-in-use at 3 caps/day in V4 (Source Naturals Magtein), pairing with Mg glycinate for systemic Mg coverage. The brain-penetrant angle is the key value-add — most Mg forms barely move CSF concentration; Magtein measurably does.

▸ Mechanism of action

Magnesium L-threonate is a chelate of magnesium with L-threonic acid (a vitamin C metabolite). The pharmacology rides on the threonate counter-ion, not on any unique elemental Mg property.

The CSF-penetration claim:

Most magnesium salts (oxide, citrate, glycinate, malate, sulfate) raise serum Mg modestly but do not measurably raise CSF Mg in animal or human studies
Magtein raises CSF Mg by ~15% in rats at equivalent oral doses (Slutsky 2010)
The mechanism is debated: hypothesized that L-threonate alters the BBB transporter chemistry for Mg, or that the chelate survives gut passage and is taken up into brain tissue more efficiently
L-threonate itself crosses the BBB and may have independent neurotrophic effects

Why CSF Mg matters:

Mg is the physiological gatekeeper of NMDA receptors — it sits in the channel pore in a voltage-dependent block, preventing excitotoxic Ca²⁺ influx
CSF Mg deficiency is implicated in chronic pain sensitization, migraine, and cognitive decline
Animal models (Slutsky 2010, Sun 2016) show Magtein increases hippocampal synaptic density (synapsin I, PSD-95) and rescues age-related memory decline in rats

Other Mg roles (shared with all Mg forms):

Cofactor for >300 enzymes including ATP synthesis, DNA replication, glucose metabolism
Required for muscle relaxation, vascular tone, sleep architecture
Antagonizes calcium influx (the basis for the migraine-prevention and muscle-cramp use cases)

▸ Pharmacokinetics No data

Pharmacokinetics data not available for this compound.

No half-life mentions found in the source notes.

▸ What to expect Generic

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Week 1

Tolerability and dose-response.
2

Week 2-4

Early effect window.
3

Week 4-8

Peak benefit assessment.
4

Week 8+

Cycle decision point.

▸ Side effects + safety

Common (>10%): Loose stool at high doses (>3 g Magtein/day); generally less than Mg oxide
Less common (1-10%): Mild headache during initial week; vivid dreams
Rare-serious (<1%): Hypotension at very high Mg doses (irrelevant at Magtein practical doses); renal Mg overload only in severe CKD
Specific watch periods: None unique to Magtein

▸Interactions8 compounds

citicoline:Synergistic
Both NMDA-modulators; Mg is the channel block, citicoline supports membrane substrate. Already paired in V4.
agmatine:Synergistic
Mg is voltage-dependent NMDA block; agmatine adds GluN2B-preferential channel block. Clean overlap.
lithium-orotate:Synergistic
Both are GSK-3β / brain-protection adjuncts; complementary not redundant
n-acetyl-cysteine:Synergistic
Glutamate modulation upstream; complementary
L-tryptophan / glycine (sleep):Synergistic
Mg supports sleep architecture; tryptophan/glycine supply substrate for serotonin/melatonin and GABAergic tone
DHA / fish oil:Synergistic
Membrane fluidity + Mg-dependent enzymes both upstream
High-dose calcium supplements (>1 g/day) at the same dose:Avoid
Compete for absorption; separate by 2 h
Quinolone or tetracycline antibiotics:Avoid
Mg chelates and reduces antibiotic absorption; separate by 2-4 h