Magnesium threonate

non-nutrient/non-botanicalthreonate

What is it

Magnesium L-threonate (sold as Magtein) is a chelated form of magnesium bound to threonic acid, a metabolite of vitamin C. It was developed at MIT specifically to enhance magnesium delivery to the brain and is most commonly marketed for cognitive function, sleep, and memory.

How it works

Like other magnesium forms, magnesium L-threonate provides elemental magnesium to support hundreds of enzymatic reactions involved in energy metabolism, neuromuscular function, and protein synthesis. What sets it apart is preclinical evidence that the threonate carrier may facilitate transport across the blood-brain barrier, raising magnesium concentrations in cerebrospinal fluid more effectively than other forms in animal studies. In rodent studies, magnesium L-threonate increased brain magnesium levels and was associated with improvements in synaptic density, NMDA receptor function, and various measures of learning and memory. Whether these brain-specific effects also occur in humans at typical supplement doses remains uncertain, but the form is widely used for cognitive and sleep support based on this mechanism. The elemental magnesium content of magnesium L-threonate is relatively low (about 7-8% by weight), so larger total doses are needed to deliver the same elemental magnesium as other forms.

Evidence for 5 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Cognitive function and memory

Grade C

Moderate evidence

A small randomized trial in older adults with cognitive impairment showed improvements in working memory and executive function with 1,500-2,000 mg/day of magnesium L-threonate. Animal studies show robust effects on synaptic density and learning. Human evidence is preliminary.

Sleep quality

Grade C

Moderate evidence

Some small trials and many user reports describe improved sleep onset and quality with evening dosing. Magnesium itself supports GABAergic and parasympathetic tone, which may explain effects regardless of form.

Anxiety

Grade C

Moderate evidence

Magnesium supplementation in general has modest evidence for anxiety reduction; whether L-threonate offers brain-specific advantages is unproven. Most data come from animal studies.

Migraine prevention

Grade C

Moderate evidence

Magnesium broadly has evidence for migraine prevention. L-threonate has not been specifically studied for this indication but may be a reasonable choice for those wanting brain-targeted dosing.

ADHD / focus

Grade D

Mixed evidence

Some small studies suggest magnesium status may influence attention. L-threonate specifically lacks clinical evidence for ADHD.

2 commercial forms

Magtein (branded magnesium L-threonate)

Patented form with the most preclinical research on brain magnesium uptake.

The form used in nearly all clinical research. Most third-party products are based on Magtein.

Generic magnesium L-threonate

Chemically equivalent to Magtein but may vary in quality control.

Often more affordable. Quality varies by manufacturer.

Dosage

Typical supplement doses are 1,000-2,000 mg of magnesium L-threonate per day, providing 144-288 mg of elemental magnesium. The dose used in human cognitive studies is 1,500-2,000 mg/day, often divided into morning and evening doses. The RDA for total elemental magnesium is 400-420 mg/day for men and 310-320 mg/day for women, with a UL of 350 mg from supplements (the UL applies to supplemental magnesium and does not include food sources).

When and how to take it

Magnesium L-threonate is often dosed twice daily, with a smaller dose in the morning and a larger dose 1-2 hours before bedtime. The evening dose is favored for its potential to support sleep and overnight magnesium delivery to the brain. Take with or without food. Separate from antibiotics, thyroid medication, and bisphosphonates by at least 2-4 hours.

Safety

Magnesium L-threonate is generally well-tolerated. Because of its lower elemental magnesium content, it tends to cause less GI upset and diarrhea than magnesium oxide or citrate. Side effects can include drowsiness or headache. Total supplemental magnesium should stay below 350 mg of elemental magnesium per day from non-food sources unless directed otherwise.

Who should be cautious

People with kidney impairment should not supplement magnesium without clinician guidance, since impaired excretion can cause dangerous accumulation. Pregnant and lactating women should consult their clinician. The form has not been widely studied in children. People on medications listed above should separate dosing.

Interactions

Magnesium can reduce absorption of tetracycline and quinolone antibiotics, bisphosphonates, and levothyroxine if taken simultaneously; separate by 2-4 hours. May enhance effects of muscle relaxants and certain blood pressure medications. Combined with other magnesium supplements, can push total intake too high. Diuretics, proton pump inhibitors, and aminoglycosides can lower magnesium status.

Frequently asked questions

Is magnesium threonate really better for the brain?⌄

Animal studies clearly show it raises brain magnesium levels more than other forms. Human evidence is limited but suggestive. If brain effects are your goal, it is a reasonable choice; for muscle, sleep, or constipation, other forms work as well or better.

How much elemental magnesium am I getting?⌄

Magnesium L-threonate is only about 7-8% elemental magnesium. A 2,000 mg dose provides roughly 144-160 mg of elemental magnesium, less than the same weight of magnesium citrate or oxide.

When should I take it?⌄

Many users take a smaller dose in the morning and a larger dose 1-2 hours before bed to support sleep and overnight brain magnesium delivery.

Can I combine it with other magnesium?⌄

Yes, but watch total elemental magnesium intake. Keep total supplemental magnesium under 350 mg/day unless directed by a clinician.

Is it worth the price?⌄

Magnesium L-threonate is significantly more expensive than other magnesium forms. If you specifically want brain-targeted dosing for cognition or sleep, it may be worthwhile. For general magnesium support, cheaper forms work fine.

References

  • Magnesium L-threonate cognitive trial — PubMed (Liu et al.) link
  • Magnesium L-threonate - Wikidata — Wikidata link

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.