MineralPart of: Magnesium

Magnesium L-threonate

Also called magnesium threonate, MgT, L-TAMS, Magtein, MMFS-01

By Kymata Health editorial teamLast reviewed October 8, 2026 · What changed

Kymata Health may earn a commission from links on separate product pages. This page contains no product links. Educational reference, not medical advice.

Summary

Magnesium L-threonate is magnesium bound to L-threonic acid, about 8% elemental magnesium by weight. Small randomized trials of 1–2 g/day for 3 to 12 weeks report better scores on cognitive tests (grade C) and mixed results for sleep (grade C). The brain-magnesium rationale comes from rat studies.

Top graded outcomes:C evidence grade Overall cognitive performanceC evidence grade Sleep quality

Key facts

What it is
Magnesium salt of L-threonic acid, Mg(C4H7O5)2; sold under the trademark Magtein[2]
Elemental magnesium
8.3% of compound weight (anhydrous): 2 g compound ≈ 165 mg magnesium[2]
Studied outcomes
Overall cognitive performance ↑ (C); sleep quality: mixed (C)[3][4][5]
Studied doses
1–2 g/day of compound for 3–12 weeks[5][3]
Absorption
No head-to-head human absorption data; raised brain magnesium in rats[6]
RDA / upper limit
Adults 310–420 mg/day magnesium (all sources); UL 350 mg/day from supplements[1]
Evidence base
2 graded human outcomes on this page
Last reviewed
October 8, 2026

How it works

ProposedIn rats, magnesium L-threonate raised brain magnesium and increased hippocampal synapse density, alongside better learning and memory (animal data). Whether the same happens in people has not been measured directly; the human trials report test scores, not brain magnesium.[6]

What the human research says

Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.

At a glance: strongest evidence per outcome

Evidence at a glance: strongest human evidence per outcome
OutcomeGradeEffectStrongest evidenceRows
FocusGrade CImprovedRCT · n = 100 · 2025Form tested: magnesium L-threonate (Magtein)1 rowIncludes this form
SleepGrade CMixedRCT · n = 80 · 2024Form tested: magnesium L-threonate1 rowIncludes this form

Every graded row

Outcome
Form tested
Sort

Showing 2 of 2 outcomes. Human trials only.

OutcomeEffectGradeBest evidencePMID
Overall cognitive performanceImprovedGrade C

RCT · n = 100 · 2025

Adults aged 18–45 with self-reported dissatisfied sleep

Form: magnesium L-threonate (Magtein) · Dose: 2 g/day compound (≈165 mg magnesium) · Duration: 6 weeks

Greater improvement than placebo on the NIH Toolbox total cognition composite (p = 0.043) and reaction time; no difference on Raven's matrices.

41601871 (opens PubMed)Source [3]
Sleep qualityMixedGrade C

RCT · n = 80 · 2024

Adults aged 35–55 with self-reported sleep problems

Form: magnesium L-threonate · Dose: 1 g/day compound (≈83 mg magnesium) · Duration: 21 days

Ring-measured deep and REM sleep scores and several self-rated daytime measures improved versus placebo. In a 6-week trial of 2 g/day (n=100), ring-measured sleep did not differ and only some self-rated measures improved, so results are mixed.

39252819 (opens PubMed)Source [5]

Forms

FormElemental %Absorption (human data)GI toleranceStudied for
Magnesium glycinate (bisglycinate)14.1%[7]Mg(C2H4NO2)2, MW 172.42; Mg 24.305 g/mol (anhydrous)In 12 people with ileal resection, overall absorption of a 100 mg dose did not differ from oxide (23.5% vs 22.8%), but was higher in the 4 with the poorest oxide absorption (23.5% vs 11.8%).[8]Better tolerated than oxide by all 12 patients in that small crossover trial.[8]Insomnia severity in adults reporting poor sleep (one RCT).
Magnesium citrate16.2%[9]Trimagnesium dicitrate Mg3(C6H5O7)2, MW 451.12 (anhydrous)More soluble and more bioavailable than oxide by urinary magnesium in short studies; in a 60-day RCT (n=46) citrate gave the highest serum magnesium of the forms compared.[10][11]Diarrhea was reported by 18.6% of participants at 600 mg/day in a 12-week migraine trial.[12]Arterial stiffness and blood pressure (null), bone-turnover markers, migraine attack frequency.
Magnesium L-threonate8.3%[2]Mg(C4H7O5)2, MW 294.50 (anhydrous); commercial ingredient may differNo head-to-head human absorption data. Raised brain magnesium in rats (animal data).[6]Described as well tolerated in 3- to 6-week trials of 1–2 g/day.[5][3]Cognitive test performance and sleep quality (small RCTs).
Elemental magnesium in 1,000 mg of each form

Arithmetic from the elemental percentages in the table above. More elemental content per gram says nothing about absorption or tolerance.

Compound weight → elemental magnesium

500 mg magnesium glycinate (bisglycinate) ≈ 71 mg elemental magnesium

Arithmetic only, from the elemental fractions in the table above. US Supplement Facts panels list the elemental amount; front-of-pack claims sometimes give the compound weight. Real products vary with hydration state and buffering.

Studied doses

Doses studied in human trials ranged from 1 to 2 g/day of magnesium L-threonate (about 83 to 165 mg of elemental magnesium), for 3 to 12 weeks.[5][3][4][2]

Intake reference: Adult RDA 310–420 mg/day from all sources (by age and sex). Upper limit for supplemental magnesium: 350 mg/day for adults.[1] The upper limit covers supplements and medicines only, not magnesium in food. NIH ODS fact sheet (updated January 6, 2026).

These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.

Interactions

Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.

Medicines

  • Oral bisphosphonatesNIH fact sheete.g. alendronate (Fosamax)Magnesium-rich supplements or medicines can reduce bisphosphonate absorption; NIH ODS notes separating them by at least 2 hours.[1]
  • Tetracycline and quinolone antibioticsNIH fact sheete.g. doxycycline, ciprofloxacin, levofloxacinMagnesium can form insoluble complexes with these antibiotics; NIH ODS notes taking the antibiotic at least 2 hours before or 4–6 hours after magnesium.[1]
  • Potassium-sparing diureticsNIH fact sheete.g. amiloride, spironolactoneReduce urinary magnesium excretion.[1]

Medicines that can lower levels

  • Loop and thiazide diureticsNIH fact sheete.g. furosemide, bumetanide, hydrochlorothiazideLong-term use can increase urinary magnesium loss and lead to depletion.[1]
  • Proton pump inhibitors (long-term)FDA safety communicatione.g. esomeprazole, lansoprazoleUse typically longer than a year can cause low blood magnesium; in about 25% of cases FDA reviewed, supplements did not correct it and the PPI was stopped.[17][1]

Other supplements

  • High-dose zincPK studye.g. 142 mg/day zinc (as zinc sulfate)Lowered magnesium absorption and magnesium balance in a metabolic-ward study of adult men.[18]

Who should be careful

Kidney problems
The risk of magnesium toxicity rises with impaired kidney function, because the kidneys remove excess magnesium.[1]
High intakes and digestive effects
High doses from supplements or medicines often cause diarrhea, nausea and abdominal cramping. The adult upper limit for supplemental magnesium is 350 mg/day; very large doses from laxatives or antacids (typically over 5,000 mg/day) have caused toxicity.[1]
Pregnancy and breastfeeding
The RDA is 350–400 mg/day in pregnancy and 310–360 mg/day during lactation (all sources), and the 350 mg/day upper limit for supplemental magnesium still applies.[1]
Children
Upper limits for supplemental magnesium are lower: 65 mg/day at ages 1–3 and 110 mg/day at ages 4–8.[1]

Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.

Frequently asked questions

What is Magtein?

Magtein is a trademarked magnesium L-threonate ingredient. The trials on this page tested Magtein or magnesium L-threonate formulations at 1–2 g/day of the compound.[3][5]

How much elemental magnesium is in magnesium L-threonate?

About 8.3% by weight for the anhydrous compound, so 2 g carries roughly 165 mg of magnesium. That is less magnesium per gram than glycinate (14.1%) or citrate (16.2%).[2][7][9]

Does magnesium L-threonate get into the brain?

In rats it raised brain magnesium. That has not been measured directly in human trials, which report cognitive test scores and sleep outcomes instead.[6]

Does magnesium L-threonate improve sleep?

Results are mixed. A 21-day trial of 1 g/day found better ring-measured deep and REM sleep scores than placebo; a 6-week trial of 2 g/day found no difference in ring-measured sleep and improvement in only some self-reported measures.[5][3]

Sources

  1. [1]Magnesium: Fact Sheet for Health Professionals (updated January 6, 2026). NIH Office of Dietary Supplements, 2026. fact-sheet
  2. [2]Magnesium L-threonate (CID 45489777): C8H14MgO10, MW 294.50. PubChem, NIH, 2026. database
  3. [3]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. RCT PMID 41601871
  4. [4]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. RCT PMID 26519439
  5. [5]Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: A randomized controlled trial.. Sleep Med X, 2024. RCT PMID 39252819
  6. [6]Enhancement of learning and memory by elevating brain magnesium.. Neuron, 2010. animal-study PMID 20152124
  7. [7]Magnesium glycinate (CID 84645): C4H8MgN2O4, MW 172.42. PubChem, NIH, 2026. database
  8. [8]Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection.. JPEN J Parenter Enteral Nutr, 1994. crossover-RCT PMID 7815675
  9. [9]Trimagnesium dicitrate (CID 6099959): C12H10Mg3O14, MW 451.12. PubChem, NIH, 2026. database
  10. [10]Magnesium bioavailability from magnesium citrate and magnesium oxide.. J Am Coll Nutr, 1990. PK-study PMID 2407766
  11. [11]Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study.. Magnes Res, 2003. RCT PMID 14596323
  12. [12]Prophylaxis of migraine with oral magnesium: results from a prospective, multi-center, placebo-controlled and double-blind randomized study.. Cephalalgia, 1996. RCT PMID 8792038
  13. [13]Magnesium malate (CID 164748): C4H4MgO5, MW 156.38. PubChem, NIH, 2026. database
  14. [14]Magnesium taurate (CID 13343447): C4H12MgN2O6S2, MW 272.6. PubChem, NIH, 2026. database
  15. [15]Magnesium oxide (CID 14792): MgO, MW 40.305. PubChem, NIH, 2026. database
  16. [16]Bioavailability of US commercial magnesium preparations.. Magnes Res, 2001. PK-study PMID 11794633
  17. [17]FDA Drug Safety Communication: Low magnesium levels can be associated with long-term use of proton pump inhibitor drugs (PPIs). U.S. Food and Drug Administration, 2011. safety-communication
  18. [18]Inhibitory effects of zinc on magnesium balance and magnesium absorption in man.. J Am Coll Nutr, 1994. PK-study PMID 7836627

What changed

  1. October 8, 2026 · all · new pageFirst published.Writer: Kymata Health editorial team · No credentialed reviewer yet

How we write, grade and correct these pages: editorial and evidence policy.

Supplement & Nutrient Encyclopedia. Educational information only; it is not medical advice and does not replace a clinician. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Statements about supplements have not been evaluated by the FDA.