What Is Magnesium L-Threonate and How Does It Work?

Magnesium helps power more than 300 different chemical reactions in the body, from converting food into energy to keeping nerves and muscles working properly.³It's one of the most essential minerals we need, and yet around half of the US population falls short of the recommended daily intake.²

Supplementation can help close that gap, and there are many well-absorbed forms of magnesium available for general health needs.⁴ But when it comes to brain health, many magnesium supplements have limited ability to cross the blood-brain barrier (the tightly controlled filter that decides what reaches brain tissue). So even if you're supplementing, much of that magnesium may never reach the brain cells that need it.

That gap between blood levels and brain levels is what magnesium L-threonate was created to address. Magtein®, the patented and clinically studied form, uses a different transport pathway that may move magnesium into the brain more effectively than standard forms. And recent clinical research suggests it's working, with a 2025 study finding meaningful improvements in memory, attention, and overall cognitive performance within six weeks.²

This article covers what magnesium L-threonate is, how it reaches the brain, what clinical research has found, how to take it, and how it compares to other forms of magnesium supplements.

Key Takeaways

Most forms of magnesium have a hard time reaching the brain. Magnesium L-threonate uses the brain's own glucose transporters to help carry more magnesium across the blood-brain barrier.²
Magtein® is the patented, clinically studied form of magnesium L-threonate.*
Some benefits like better sleep and daytime alertness may show up within the first few weeks of daily use.¹
In a 2026 published study, six weeks of daily Magtein use was associated with a statistically significant improvement on a research-based measure of cognitive age.²

What Does Magnesium Do in the Body?

Magnesium helps convert food into energy, supports nerve and muscle function, plays a role in blood pressure and blood sugar regulation, and is needed to produce DNA and the antioxidant glutathione.³

Because it touches so many systems, running low might show up as general symptoms like fatigue, weakness, muscle cramps, or loss of appetite.³

Magnesium and Sleep

Magnesium's relationship with sleep has been a growing area of research, and there are a few reasons why:⁶

Magnesium helps regulate GABA, a neurotransmitter that calms neural activity and promotes relaxation, making it easier for the brain to wind down at the end of the day.
It also appears to play a role in the production of melatonin, the hormone that helps set your body's sleep-wake cycle.

A large longitudinal study following nearly 4,000 young American adults found that higher magnesium intake was associated with better sleep quality and a lower likelihood of sleeping fewer than seven hours per night.⁶ Other research has found that low plasma magnesium levels are more common in people who are sleep deprived.¹

These findings help explain why magnesium supplementation has become popular for sleep support, though results have varied depending on the form of magnesium used.² That variability is part of what makes the form you choose worth paying attention to.

Magnesium and the Brain

Magnesium is especially important for how the brain functions. It helps brain cells send and receive chemical signals, supports the enzymes that keep those cells functioning, and contributes to the processes behind learning, memory, and focus.*

One area where magnesium is especially relevant is at the synapses, the connection points between brain cells where new information gets processed and stored. Research in animal models suggests that higher magnesium levels in the brain can support both the number of synaptic connections and the brain's ability to strengthen and reorganize them over time.⁵ Magnesium also helps brain cells produce the energy they need to stay active and responsive, which is especially important because brain cells are some of the most energy-hungry cells in the body.*

The challenge is that the brain is a hard place for magnesium to reach because the blood-brain barrier is extremely selective, and most supplemental forms of magnesium have limited ability to cross it.²

What Is Magnesium L-Threonate?

Magnesium L-threonate, or simply magnesium threonate, is a compound that pairs magnesium with L-threonic acid, a substance your body already produces naturally when it metabolizes vitamin C.⁵ That pairing is what makes this form different from other magnesium supplements.

While every form delivers elemental magnesium to the body, the L-threonic acid portion acts as a carrier that can reach the brain more readily. Preclinical research has shown that it travels through glucose transporters, the same channels the brain relies on to take in fuel, to carry magnesium across the blood-brain barrier and into brain tissue. Animal studies confirm that this leads to meaningfully higher magnesium concentrations in the brain compared to other supplemental forms.²

Magtein® is the patented form of magnesium L-threonate and the one used in published clinical trials on cognitive performance, sleep quality, and brain aging.^1,2,5 It's also the form featured in Metagenics' Magnesium L-Threonate supplement. Every batch is third-party tested for purity, potency, and contaminants.*

Magnesium L-threonate is designed to cross the blood-brain barrier, supporting brain cell connections and cellular energy for cognitive performance.*

What the Research Says About Magnesium L-Threonate Benefits

The most comprehensive study on Magtein to date is a 2025 randomized, double-blind, placebo-controlled trial published in Frontiers in Nutrition. The study followed 100 healthy adults between the ages of 18 and 45 who took 2 grams of Magtein daily for six weeks.²

Participants who took Magtein showed significant improvements on a cognitive test that measures things like working memory, the ability to recall past experiences, and processing speed. Those improvements were associated with statistically significant changes on a research-based measure of cognitive age compared to what would be expected for their age group.²The Magtein group also responded faster on timed tasks, suggesting sharper real-time mental processing.

On the sleep side, participants taking Magtein reported feeling less impaired by poor sleep during the day, and they experienced lower resting heart rate and improved heart rate variability (a measure of how well your body recovers and shifts between alertness and rest) during sleep. It's worth noting that the study did not find significant differences between groups on objective sleep measures tracked by wearable devices. The sleep-related benefits appeared to be more about how participants felt and functioned during the day than about measurable changes in sleep duration or sleep stages.

Research on Magtein® suggests benefits for cellular energy, working memory, focus, and overall cognitive performance.*

Is Magnesium L-Threonate Safe?

In the clinical trials on Magtein, the supplement was consistently well-tolerated. The 6-week trial reported no significant adverse events, and the 3-week trial recorded fewer adverse events in the Magtein group than in the placebo group.^1,2

Still, high doses of any form of magnesium can sometimes cause digestive discomfort like loose stools or nausea. The NIH sets the tolerable upper intake level for supplemental magnesium at 350 mg per day for adults.³ For context, the recommended daily dose of Metagenics Magnesium L-Threonate is well within that range.

One thing worth knowing about Metagenics specifically: every batch of Mag L-Threonate goes through independent third-party lab testing for purity, potency, and safety, including screening for heavy metals, contaminants, and microbes.* The product is made in GMP and NSF-certified facilities, and across their full product line, Metagenics runs over 200,000 quality tests per year.* The capsules are vegetarian, and the formula is non-GMO, gluten-free, lactose-free, and free from artificial preservatives.*

How Long Does It Take to See Results?

Based on the available clinical research, self-reported improvements like feeling more rested, more alert during the day, or in a better mood may appear within the first few weeks of daily use.¹ Scientifically measurable improvements have taken longer to develop in studies, with the most significant results appearing around the four-to-six-week mark.^2,5

What do these improvements actually feel like? The studies measured things like faster reaction times and better memory scores, but in everyday life that might look like recalling a name more easily, staying focused through a long meeting, or waking up feeling more clear-headed. Think of it like the difference between a day when you've had a good lunch and your afternoon coffee versus a day when you had to work through your lunch break.

What to Expect

Results vary by person, but some studies have observed:

Weeks 1-2: Early, self-reported improvements in deep sleep quality and daytime alertness¹
Weeks 3-4: Gradual improvements in memory and cognitive function⁵
Week 6: Significant measurable improvements in overall cognitive function²

How to Take Magnesium L-Threonate

The recommended daily dose of Metagenics Mag L-Threonate is three capsules, providing 2 grams of Magtein® and 144 mg of elemental magnesium (35% of the daily value).*

Take one easy-to-swallow capsule in the morning and two capsules approximately two hours before bedtime, or as directed by your healthcare practitioner.* If you're already taking another form of magnesium for general health, check with your healthcare practitioner about your total daily intake.

The recommended daily dose is three capsules: one in the morning and two approximately two hours before bedtime.*

If you're pregnant, nursing, taking medication, or managing a health condition, check with your healthcare practitioner before adding any new supplement.

Magnesium L-Threonate vs. Magnesium Glycinate

Magnesium glycinate pairs magnesium with the amino acid glycine and is one of the more bioavailable forms of supplemental magnesium.⁴ It's commonly recommended for general magnesium replenishment, muscle relaxation, and sleep support.* Magnesium L-threonate was developed more specifically to cross the blood-brain barrier and support cognitive function.

The key difference comes down to where each form was designed to work. Glycinate is well-absorbed in the gut and widely used for whole-body magnesium needs, while magnesium threonate was specifically developed to increase magnesium levels in the brain. Neither one is better in an absolute sense; they just have different strengths and different research behind them. Exploring the different types of magnesium supplements and their intended uses can help you pick the best one for your specific needs.

Frequently Asked Questions

Can magnesium threonate help with brain fog?

Some research suggests it may help. Study participants taking Magtein showed improvements in the kinds of cognitive functions people often associate with brain fog, like working memory and processing speed. ²

Can magnesium L-threonate help with anxiety?

Magnesium L-threonate is designed primarily for cognitive support, not as an anxiety treatment. That said, research on Magtein has found improvements in sleep quality, daytime alertness, and mood,¹ and poor sleep is closely linked to increased feelings of stress and anxiety. By supporting better sleep, Magtein may indirectly help with some of the factors that contribute to anxiety.

Can I take magnesium L-threonate with other supplements?

Check with your healthcare practitioner about your full supplement routine. The elemental magnesium in Metagenics Magnesium L-Threonate falls well within the NIH's tolerable upper intake level for supplemental magnesium.³

The Bottom Line

If you've read this far, you probably came in with a question about whether magnesium L-threonate is worth trying. The research is still growing, but what's been published so far is encouraging, particularly for people who want to be proactive about cognitive health. And unlike a lot of wellness trends that rely on how something feels, the clinical research on Magtein® has measured real, quantifiable improvements in cognitive function.²

Metagenics offers Magtein in a straightforward daily supplement as well as part of a more comprehensive brain health daily pack for people who want broader nutritional support. If sleep and stress are also on your radar, it's worth browsing the full stress, mood, and sleep category to see what else might fit.

Want to learn more about magnesium and supplementation? Try these articles next:

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

References

Hausenblas HA, Lynch T, Hooper S, Shrestha A, Rosendale D, Gu J. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: A randomized controlled trial. Sleep Medicine: X. 2024;8:100121.
Lopresti, Adrian & Smith, Stephen. (2026). The effects of magnesium L-threonate (Magtein) on cognitive performance and sleep quality in adults: a randomised, double-blind, placebo-controlled trial. Frontiers in Nutrition. 12. 1729164. 10.3389/fnut.2025.1729164.
National Institutes of Health Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. Updated January 6, 2026. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
Pardo, M. R., Garicano Vilar, E., San Mauro Martín, I., & Camina Martín, M. A. (2021). Bioavailability of magnesium food supplements: A systematic review. Nutrition, 89, 111294. https://doi.org/https://doi.org/10.1016/j.nut.2021.111294
Zhang, C., Hu, Q., Li, S., Dai, F., Qian, W., Hewlings, S., Yan, T., & Wang, Y. (2022). A Magtein®, Magnesium L-Threonate, -Based Formula Improves Brain Cognitive Functions in Healthy Chinese Adults. Nutrients, 14(24), 5235. https://doi.org/10.3390/nu14245235
Zhang, Y., Chen, C., Lu, L., Knutson, K. L., Carnethon, M. R., Fly, A. D., Luo, J., Haas, D. M., Shikany, J. M., & Kahe, K. (2022). Association of magnesium intake with sleep duration and sleep quality: findings from the CARDIA study. Sleep, 45(4), zsab276. https://doi.org/10.1093/sleep/zsab276