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Magnesium L-Threonate (Magtein)

Evidence Level
Moderate
2 Clinical Trials
4 Documented Benefits
3/5 Evidence Score

Magnesium L-threonate is the magnesium salt of L-threonic acid, sold most often under the branded name Magtein. It is the one magnesium form shown to cross the blood-brain barrier and raise magnesium levels in the brain in meaningful amounts, which is why it is chosen when the goal is cognition, memory, or a racing mind rather than general magnesium repletion. Human trials report improvements in cognitive performance, sleep quality, and daytime functioning, though the studied doses are high (1,000 to 2,000 mg of the compound) and deliver only about 144 mg of elemental magnesium. It is gentle on the gut but the most expensive magnesium form.

Studied Dose 1,000 to 2,000 mg of magnesium L-threonate per day (about 144 mg elemental magnesium), commonly split into two or three doses with a portion in the evening.
Active Compound Magnesium L-threonate, the magnesium salt of L-threonic acid (branded as Magtein); about 7.2% elemental magnesium by weight.

Benefits

Cognition and Memory

Magnesium L-threonate is the magnesium form best studied for the brain. In a randomized trial in older adults with cognitive complaints (MMFS-01), it improved overall cognitive scores versus placebo, with the largest gains in those who started with greater executive-function deficits.

Supported by Trial 1

Sleep Quality

Randomized controlled trials in adults with self-reported sleep problems found that magnesium L-threonate improved sleep quality and next-day functioning, with reports of more restful sleep and better mood on waking.

Supported by Trial 2

Brain Magnesium Delivery

Unlike most forms, L-threonate raises magnesium concentrations in the brain and cerebrospinal fluid in preclinical work, which is the basis for using it when the target is mental rather than muscular or digestive.

Supported by Trial 1, Trial 2

Calm and a Quieter Mind

By supporting healthy magnesium status and the balance between excitatory NMDA and calming GABA signaling, it may help with stress and a busy mind at bedtime. It is not a treatment for an anxiety disorder.

Supported by Trial 1, Trial 2

Mechanism of action

1

Crosses the Blood-Brain Barrier

The threonate carrier enables magnesium uptake into the central nervous system, raising brain and cerebrospinal-fluid magnesium where most other forms have limited reach.

2

Synaptic Density and Plasticity

Elevating brain magnesium increased synapse density and enhanced learning and memory in preclinical models, by supporting NMDA-receptor function and synaptic plasticity.

3

NMDA and GABA Modulation

Like all magnesium, it dampens excitatory NMDA-receptor signaling and supports inhibitory GABA tone, shifting the nervous system toward calm and easier sleep onset.

Clinical trials

1
MMFS-01 in Older Adults with Cognitive Impairment
PubMed

Randomized, double-blind, placebo-controlled trial. Liu G et al., J Alzheimers Dis 2016;49(4):971-90.

Older adults aged 50 to 70 with cognitive complaints and anxiety.

Magnesium L-threonate (MMFS-01) significantly improved overall cognitive ability versus placebo, with the largest effect in participants who had greater baseline executive-function deficits.

2
Sleep Quality and Daytime Functioning RCT
PubMed

Randomized controlled trial. Hausenblas HA et al., Sleep Med X 2024;8:100121.

Adults with self-reported sleep problems.

Magnesium L-threonate improved self-reported sleep quality and daytime functioning versus placebo over the study period.

Side effects and drug interactions

Common Potential side effects

Generally well tolerated and gentle on the stomach, with little of the laxative effect seen with citrate or oxide.
High capsule load: the studied dose is 1,000 to 2,000 mg of the compound, usually two to three capsules per day.
Occasional headache, drowsiness, or restlessness; taking part of the dose earlier in the day can help.
Excess magnesium from any form can cause diarrhea, though this is less common with threonate.

Important Drug interactions

Bisphosphonates (alendronate, risedronate): magnesium reduces their absorption; separate doses by at least 2 hours.
Tetracycline and fluoroquinolone antibiotics: magnesium binds them and lowers absorption; space several hours apart.
Reduced kidney function: magnesium can accumulate; use only under medical supervision.

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Frequently asked questions about Magnesium L-Threonate (Magtein)

What is magnesium L-threonate good for?

It is the magnesium form best studied for the brain. It crosses into the central nervous system and is used for memory, focus, and a racing mind, with trials also reporting better sleep quality. For general sleep and anxiety on a budget, magnesium glycinate is the more common first choice.

How much magnesium L-threonate should I take?

Studies use about 1,000 to 2,000 mg of the compound per day, which provides roughly 144 mg of elemental magnesium. It is usually split into two or three doses, with part taken in the evening. Keep your total magnesium intake sensible and check with your doctor if you have kidney problems.

What is Magnesium L-Threonate (Magtein)?

Magnesium L-threonate is the magnesium salt of L-threonic acid, sold most often under the branded name Magtein. It is the one magnesium form shown to cross the blood-brain barrier and raise magnesium levels in the brain in meaningful amounts, which is why it is chosen when the goal is cognition, memory, or a racing min…

What is the recommended dosage of Magnesium L-Threonate (Magtein)?

The clinically studied dose for Magnesium L-Threonate (Magtein) is 1,000 to 2,000 mg of magnesium L-threonate per day (about 144 mg elemental magnesium), commonly split into two or three doses with a portion in the evening.. Always follow product labeling and consult a healthcare provider for personalized dosing recommendations.

What is Magnesium L-Threonate (Magtein) used for?

Magnesium L-Threonate (Magtein) is studied for cognition and memory, sleep quality, brain magnesium delivery. Magnesium L-threonate is the magnesium form best studied for the brain. In a randomized trial in older adults with cognitive complaints (MMFS-01), it improved overall cognitive scores versus placebo, with the largest gains in those who started with g…

References(4 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Slutsky I, Abumaria N, Wu LJ, et al. Enhancement of learning and memory by elevating brain magnesium. Neuron. 2010;65(2):165-77. doi: 10.1016/j.neuron.2009.12.026.PubMedUsed to support: Foundational preclinical work showing magnesium L-threonate raises brain magnesium and enhances learning, memory, and synapse density.
  2. Liu G, Weinger JG, Lu ZL, et al. Efficacy and Safety of MMFS-01, a Synapse Density Enhancer, for Treating Cognitive Impairment in Older Adults: A Randomized, Double-Blind, Placebo-Controlled Trial. J Alzheimers Dis. 2016;49(4):971-90. doi: 10.3233/JAD-150538.PubMedUsed to support: Randomized trial in older adults showing magnesium L-threonate (MMFS-01) improved overall cognition versus placebo.
  3. Hausenblas HA, Lynch T, Hooper S, et al. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: A randomized controlled trial. Sleep Med X. 2024;8:100121. doi: 10.1016/j.sleepx.2024.100121.PubMedUsed to support: Randomized controlled trial showing improved sleep quality and daytime functioning with magnesium L-threonate.
  4. Lopresti AL, Smith SJ. The effects of magnesium L-threonate (Magtein) on cognitive performance and sleep quality in adults: a randomised, double-blind, placebo-controlled trial. Front Nutr. 2025;12:1729164. doi: 10.3389/fnut.2025.1729164.PubMedUsed to support: Recent randomized, double-blind trial of Magtein evaluating cognitive performance and sleep quality in adults.