Magnesium L-Threonate vs Glycinate (2026)

Quick Answer: Choose magnesium L-threonate (often Magtein®) if your main goal is cognition or brain-related research interest; human trials used about 1 to 2 g of Magtein per day (roughly 75 to 145 mg elemental magnesium, depending on the product). Choose magnesium glycinate (bisglycinate) if you want a generally well-tolerated magnesium form for everyday replenishment or sleep support; the largest glycinate sleep trial used 250 mg elemental magnesium for 4 weeks and found a small insomnia-score benefit, mainly in people who ate little magnesium. Both count toward the NIH supplemental magnesium upper limit of 350 mg a day for adults. Neither replaces medical care for insomnia, memory loss or deficiency. People with kidney disease should not use magnesium supplements without medical advice.

Magnesium L-Threonate vs Glycinate: Comparison Chart

	Magnesium L-threonate (Magtein®)	Magnesium glycinate (bisglycinate)
What it is	Magnesium salt of L-threonic acid; marketed for brain magnesium delivery	Magnesium chelated to two glycine molecules; marketed for absorption and calm/sleep
Typical studied dose	1–2 g Magtein/day (about 75–145 mg elemental Mg in cited trials)	Often 200–250 mg elemental Mg/day in sleep research; labels vary
Best studied for	Cognition in older or sleep-dissatisfied adults (small RCTs); some sleep-wearable and questionnaire findings	Sleep/insomnia scores; general magnesium replenishment with fewer GI complaints than some salts
Elemental Mg per typical scoop/capsule set	Often lower elemental Mg for the same compound weight (Magtein ~75 mg elemental Mg per gram of Magtein in one sleep trial label description)	Higher elemental Mg per serving is common (e.g., 200–250 mg)
NIH adult supplemental UL	350 mg/day elemental magnesium from supplements (food does not count toward UL)
Who often prefers it	Adults focused on memory/cognition research findings	Adults focused on sleep, stress wind-down or general magnesium intake
Cost	Usually higher per mg elemental magnesium	Usually lower per mg elemental magnesium

Sources: NIH ODS magnesium fact sheet; Liu et al. 2016 MMFS-01 trial; Hausenblas et al. 2024 Magtein sleep RCT; Frontiers Magtein 2025 cognition/sleep RCT; 2025 Nature and Science of Sleep bisglycinate RCT.

What Each Form Actually Is

Magnesium L-threonate is a magnesium salt paired with L-threonic acid (a vitamin C metabolite). Brand-name Magtein® is the form used in most published human trials. The marketing claim is better delivery of magnesium into the brain. Animal work by Slutsky, Liu and colleagues in Neuron (2010) reported learning and memory benefits in rats when brain magnesium was raised with this compound; that paper is preclinical, not a human dosing guide.

Magnesium glycinate (also labeled bisglycinate or glycinate chelate) binds magnesium to glycine. You take it primarily for the magnesium; glycine is the carrier. NIH’s Office of Dietary Supplements notes that Supplement Facts list elemental magnesium, not the weight of the whole compound. For how much glycine comes along for the ride, see our magnesium glycinate vs glycine for sleep comparison.

Both are dietary supplements, not FDA-approved drugs for cognition or insomnia. For the broader form landscape (citrate, oxide, malate and more), see magnesium types compared.

What Human Trials Show for L-Threonate

Cognition (Liu / MMFS-01, 2016)

In a randomized, double-blind, placebo-controlled trial, adults aged 50–70 with cognitive complaints took MMFS-01 (a Magtein-based formula) or placebo for 12 weeks. Dose was about 1.5 g/day for people 50–70 kg and 2 g/day for people 70–100 kg. Treated participants (n = 23) improved on a composite of cognitive tests versus placebo (n = 21), with the authors reporting p = 0.003 and Cohen’s d = 0.91 for overall cognitive ability. Sleep and anxiety effects could not be determined because of strong placebo responses. This is a small study; it does not prove Magtein treats dementia.

Sleep and daytime function (Hausenblas et al., 2024)

Eighty adults aged 35–55 with self-reported sleep problems took 1 g/day Magtein (two 500 mg capsules, about 2 hours before bed; authors state Magtein contains about 75 mg elemental magnesium per gram) or placebo for 21 days. Versus placebo, Magtein improved several Oura ring metrics (including deep sleep score and REM sleep score) and some questionnaire items on next-day energy and mood. The trial was industry-supported; treat results as promising but not definitive.

Cognition and sleep in younger adults (Frontiers, 2025)

One hundred adults aged 18–45 with self-reported dissatisfied sleep took 2 g Magtein daily (1 g morning + 1 g about 2 hours before bed; authors state 145 mg elemental magnesium) or placebo for 6 weeks. Versus placebo, Magtein improved the NIH Toolbox Total Cognition Composite (p = 0.043), with larger effects on working and episodic memory, a reported 7.5-year reduction in estimated cognitive age, and faster reaction time (p = 0.031). Self-reported sleep-related impairment improved (p = 0.043), but several other sleep questionnaires and wearable sleep outcomes did not differ between groups. Resting heart rate fell and HRV rose versus placebo. Again, sample size is modest and Magtein is a branded ingredient.

Bottom line on threonate: a few RCTs suggest cognitive benefits at 1–2 g Magtein/day, with mixed sleep findings. Evidence is still limited compared with decades of general magnesium research.

What Human Trials Show for Glycinate

The best trial of magnesium bisglycinate specifically for sleep was published in 2025 in Nature and Science of Sleep. In 155 adults aged 18–65 with poor sleep, 250 mg elemental magnesium as bisglycinate (30–60 minutes before bed) for 4 weeks produced a small improvement in Insomnia Severity Index scores versus placebo (ISI change about −3.9 vs −2.3; effect size about d = 0.2), with more benefit in people whose diets were low in magnesium.

For magnesium more generally (often oxide or citrate, not glycinate), a 2021 systematic review and meta-analysis by Mah and Pitre pooled three trials in 151 older adults and found people fell asleep about 17.36 minutes faster with magnesium; the gain in total sleep time was not statistically significant, and the authors rated evidence quality low to very low.

Glycinate is often chosen because many people find it gentler on the gut than oxide or citrate. NIH notes that magnesium carbonate, chloride, gluconate and oxide are the forms most often linked to diarrhea. Direct head-to-head RCTs of threonate versus glycinate for sleep or cognition are not listed in the sources we checked for this article.

Elemental Magnesium: Read the Label

Comparing bottles by compound weight is misleading. Magtein trials that used 1–2 g of Magtein delivered on the order of 75–145 mg elemental magnesium in the citations above. A glycinate bottle advertising 200–250 mg usually means 200–250 mg of elemental magnesium—often more magnesium mineral than a typical Magtein serving, at a lower price.

NIH RDAs for adults range from about 310 to 420 mg/day from all sources, depending on age and sex. An NHANES analysis cited by NIH found 48% of Americans get less magnesium from food and beverages than their Estimated Average Requirement. Food magnesium does not count toward the 350 mg/day Tolerable Upper Intake Level for supplemental magnesium.

Which Should You Take?

Pick L-threonate if cognition is your primary interest and you accept paying more per mg of elemental magnesium for the Magtein trial literature.
Pick glycinate if sleep, evening wind-down or affordable magnesium replenishment is the goal, especially if oxide upset your stomach.
Food first still matters: pumpkin seeds, chia, almonds, spinach and beans are among the higher-magnesium foods on the NIH ODS list.
Do not stack blindly. Add elemental magnesium across multivitamins, calm powders, Magtein and glycinate so the supplemental total stays at or under 350 mg/day unless a clinician directs otherwise.
For sleep timing questions that involve melatonin, see melatonin vs magnesium for sleep.

Safety, Side Effects and Interactions

Upper limit: 350 mg/day supplemental magnesium for adults (NIH). Excess often causes diarrhea, nausea or cramping.
Kidney disease: higher risk of magnesium toxicity when kidneys cannot clear magnesium; avoid unsupervised supplements.
Drug timing: NIH advises separating magnesium from bisphosphonates and from tetracycline or quinolone antibiotics; ask a pharmacist about diuretics and long-term PPIs.
Pregnancy and children: doses and forms should be clinician-guided; Magtein cognition trials enrolled adults, not pregnant people or kids.
Supplements are not FDA-approved to treat Alzheimer disease, insomnia disorder or psychiatric illness. Persistent sleep or memory problems need medical evaluation (ACP guidance favors CBT-I as first-line for chronic insomnia).

Doctor disclaimer: This article is for educational purposes and does not replace medical advice. Consult a licensed clinician before starting magnesium or any supplement—especially if you are pregnant, breastfeeding, have kidney disease, take prescription medicines or have unexplained memory or sleep symptoms.

Frequently Asked Questions

Is magnesium L-threonate better than glycinate?

It depends on the goal. Threonate (Magtein) has small RCTs aimed at cognition at about 1 to 2 g Magtein per day. Glycinate has a 2025 sleep RCT at 250 mg elemental magnesium with a small insomnia-score benefit, and it usually costs less per mg of magnesium. There is no large head-to-head trial of the two forms.

How much elemental magnesium is in Magtein?

It varies by product. One 2024 sleep trial stated Magtein contains about 75 mg elemental magnesium per gram; a 2025 Frontiers trial using 2 g Magtein daily described 145 mg elemental magnesium. Always read elemental magnesium on the Supplement Facts panel.

Which is better for sleep, threonate or glycinate?

Glycinate has a dedicated 155-person sleep trial showing a small benefit. Threonate sleep findings are mixed: some wearable and questionnaire improvements in short trials, but a 6-week Magtein study found limited group differences on several sleep measures. Food magnesium and sleep habits still matter more than form hype.

Can I take magnesium threonate and glycinate together?

Only if the combined elemental magnesium from all supplements stays at or under 350 mg a day for adults, unless a clinician advises otherwise. Stacking both is usually unnecessary.

What is the NIH upper limit for magnesium?

350 mg a day from supplements for adults and teens 9+. Food magnesium does not count toward that UL. Excess supplemental magnesium often causes diarrhea.

Who should avoid these supplements?

People with kidney disease should not take magnesium supplements without medical advice. Separate magnesium from bisphosphonates and certain antibiotics as NIH advises, and ask a clinician if you are pregnant, breastfeeding or have unexplained memory or sleep symptoms.

Sources

Also comparing: magnesium types, glycinate vs glycine, melatonin vs magnesium.