RetzlerRx® Magnesium L-Threonate Powder with Magtein® — Berry Flavor

Brain-focused magnesium support for cognition, memory, mental clarity, relaxation and healthy sleep-wake cycles, in an easy-to-mix berry flavor.*

RetzlerRx® Magnesium L-Threonate Powder — Berry Flavor features Magtein®, a patented and clinically studied form of magnesium L-threonate developed for brain-focused magnesium supplementation.*

Magnesium is involved in hundreds of biochemical reactions throughout the body, including nerve signaling, cellular energy production, muscle function and metabolic regulation. Magnesium L-threonate is different from many commonly used magnesium forms because much of the interest surrounding it has centered specifically on cognition, memory and neurological function.

The berry-flavored powder provides an alternative for adults who prefer mixing their magnesium into water or another beverage rather than taking multiple capsules. For some people, the flavored option may also make a consistent daily routine easier to maintain.

What Is Magnesium L-Threonate?

Magnesium L-threonate is a specialized magnesium compound formed from magnesium and threonic acid. This formula uses Magtein®, a branded magnesium L-threonate ingredient that has been studied in human clinical trials examining cognition, memory and sleep-related outcomes.

The important distinction is not that magnesium L-threonate is automatically the “best” form of magnesium for everyone. Different forms can make sense for different purposes.

If the goal is broad magnesium replacement, digestive regularity or general muscle support, another form may be perfectly reasonable. Magnesium L-threonate becomes particularly interesting when the reason for using magnesium is cognitive function, memory or brain-focused neurological support.*

Why Magtein®?

Magtein® has attracted attention because it has been studied differently from many ordinary magnesium supplements. Researchers have specifically examined cognitive performance, working memory, episodic memory, reaction time and sleep-related outcomes.

That does not make magnesium L-threonate a treatment for Alzheimer's disease, dementia, cognitive impairment or insomnia.

It does make it one of the more interesting magnesium forms when the clinical conversation is centered on brain-focused nutritional support.*

What Does the Human Research Show?

The evidence is encouraging, but it deserves to be described without turning it into more than it is.

A randomized, double-blind, placebo-controlled trial published in 2026 studied 100 adults ages 18 to 45 who reported dissatisfaction with their sleep. Participants received 2 grams of Magtein® daily or placebo for six weeks.

Compared with placebo, the Magtein® group had greater improvement in overall cognition measured with the NIH Toolbox, with stronger effects in working memory and episodic memory. Reaction time also improved.

The sleep findings were less consistent. Participants reported improvement in sleep-related impairment, but several other subjective sleep measures did not differ significantly from placebo, and wearable measurements did not show an overall improvement in objective sleep outcomes.

That distinction matters. We would not take a positive cognitive study and turn it into the claim that magnesium L-threonate has been proven to “fix sleep.”

An earlier randomized controlled trial in 80 adults with self-reported sleep problems found improvements in several subjective measures of daytime function and some sleep measures recorded with an Oura Ring after magnesium L-threonate supplementation.

Another randomized study evaluated a formula combining Magtein® with phosphatidylserine and vitamins C and D in 109 healthy adults. The combination improved several measures of memory compared with placebo, although because multiple ingredients were used, those findings cannot be attributed to magnesium L-threonate alone.

There is enough human research to make magnesium L-threonate clinically interesting. There is not enough evidence to turn it into a miracle brain or sleep supplement.

These studies evaluated Magtein® or Magtein®-containing formulations under specific research conditions. They should not be interpreted as proof that this finished RetzlerRx® product prevents or treats neurological disease, cognitive decline or a sleep disorder.

Magnesium and the Larger Brain-Health Picture

One supplement cannot carry the weight of brain health.

Cognitive function is influenced by vascular health, blood pressure, glucose regulation, sleep, physical activity, hearing, mood, medications, hormones, nutrition and other factors. Magnesium may be useful within that larger picture, but it should not replace the work of identifying what is actually driving a cognitive complaint.

Our article Magnesium and Brain Function: A Neuroplasticity Perspective looks more closely at magnesium's role in neuronal signaling, synaptic plasticity, nervous-system regulation and cognitive resilience.

For the broader clinical perspective, see Cognitive Function, Brain Health, and Longevity. Brain health is not just about supplements. It is also about cardiovascular risk, metabolism, sleep, exercise, hormones and the other systems that help determine how the brain ages.

Berry or Unflavored: Which One Makes More Sense?

The active magnesium form is the reason to choose the product. Flavor is about preference and consistency.

The berry-flavored version may make more sense for someone who prefers the taste of a flavored drink and wants magnesium to become part of an evening or daily routine.

The unflavored version may be preferable for someone who wants the simplest taste profile or plans to mix the powder into another beverage.

Neither flavor is inherently “better” for brain health. The more useful choice is the one that fits the person's preferences and is likely to be used consistently.

Our article Magnesium L-Threonate Powder: The Brain-Focused Magnesium We Use at HormoneSynergy® discusses both powder options and how they may fit into a broader cognitive and sleep-support strategy.*

What About Sleep?

Magnesium is frequently marketed as a sleep supplement. The evidence is more nuanced than the marketing.

Magnesium participates in nervous-system regulation and normal sleep physiology, and magnesium L-threonate has been studied in adults with sleep concerns. But poor sleep can also result from sleep apnea, restless legs, medications, alcohol, chronic stress, hormonal changes, circadian disruption, pain and many other causes.

A magnesium supplement should not be expected to compensate for an untreated sleep disorder.

For a broader discussion of magnesium, sleep and metabolic health, read Magnesium for Metabolic Health and Sleep: A Longevity Medicine Perspective.

How Is Magnesium L-Threonate Different From Magnesium Glycinate?

These two forms are frequently compared as though one must be better. That is not a particularly useful way to look at them.

Magnesium L-threonate is generally selected when cognition, memory and brain-focused neurological support are the priority.*

Magnesium glycinate is commonly selected for broader magnesium supplementation, relaxation, muscle function and gastrointestinal tolerability.*

For some people, glycinate may make more practical sense. For others, the brain-focused clinical research behind magnesium L-threonate is the reason to choose it.

The better question is not, “Which magnesium is best?”

It is, “Why are you taking magnesium?”

Who May Consider This Formula?

RetzlerRx® Magnesium L-Threonate Powder — Berry Flavor may be considered by adults interested in nutritional support for:

• Memory and cognitive performance*
• Mental clarity and focus*
• Healthy neurological function*
• Learning and cognitive resilience*
• Relaxation and a healthy stress response*
• Healthy sleep-wake cycles*

Persistent brain fog, progressive memory problems, significant changes in concentration or ongoing sleep disruption deserve appropriate medical evaluation. A supplement should not delay assessment of symptoms that are worsening or interfering with normal function.

Why a Berry-Flavored Powder?

Magnesium L-threonate typically requires a larger amount of ingredient material than some other forms of magnesium. For people who do not want to add several capsules to an already crowded supplement routine, powder can be a practical alternative.

The berry flavor is designed for people who prefer their magnesium mixed with water as a flavored daily drink rather than an unflavored powder.

There is no clinical advantage to choosing berry solely because it is flavored. The advantage is practical: a supplement only has the opportunity to help if it is actually used consistently.

Suggested Use

Mix according to the current product label directions or use as directed by your healthcare professional.

Individual magnesium needs vary, particularly when other magnesium-containing supplements are being used at the same time. Follow the current label for the correct serving size, amount of liquid and complete directions for this berry formulation.

Important Cautions

Consult a qualified healthcare professional before using supplemental magnesium if you are pregnant or breastfeeding, take prescription medications or have a chronic medical condition.

Kidney function matters. The kidneys play an important role in regulating magnesium balance. Individuals with impaired kidney function should seek medical guidance before using supplemental magnesium.

Magnesium can also interfere with the absorption of certain medications when taken at the same time, including some antibiotics and thyroid medications. Medication timing should be reviewed with a physician or pharmacist when appropriate.

If you already use another magnesium-containing supplement, consider total supplemental magnesium intake rather than looking at each product in isolation.

Why RetzlerRx®?

RetzlerRx® is built around a simple principle: the form of an ingredient matters.

We look for meaningful ingredient forms, clinically relevant doses, responsible formulation and appropriate quality standards. The goal is not to make every supplement sound essential. It is to have a reason for the product to exist.

Magnesium L-threonate does not need to replace every other magnesium formulation. Its place is more specific: brain-focused magnesium support backed by a growing human research literature involving the Magtein® ingredient.*

Medicine, Not Marketing

Brain health is an easy place to sell fear.

People are understandably concerned about memory, cognitive decline and maintaining independence as they age. That makes it even more important not to turn an interesting nutrient into a promise it cannot support.

Magnesium L-threonate is interesting. Human trials are encouraging. Neither statement means it prevents Alzheimer's disease, reverses cognitive decline or treats insomnia.

Long-term cognitive health still rests much more heavily on cardiovascular risk reduction, blood-pressure control, metabolic health, restorative sleep, exercise, adequate nutrition, hearing and sensory health, social connection and appropriate medical evaluation.

Supplements belong in support of that plan, not in place of it.*

Learn More

• Magnesium L-Threonate Powder: The Brain-Focused Magnesium We Use at HormoneSynergy®
• Magnesium and Brain Function: A Neuroplasticity Perspective
• Cognitive Function, Brain Health, and Longevity
• Magnesium for Metabolic Health and Sleep
• HormoneSynergy® Longevity Medicine Resource Library
• Explore RetzlerRx® Longevity Supplements

Video: Dr. Kath Retzler Explains Magnesium L-Threonate

Selected Clinical Resources

• 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. Frontiers in Nutrition. 2026.
• Hausenblas HA, et al. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: a randomized controlled trial. Sleep Medicine: X. 2024.
• Zhang C, et al. A Magtein®, Magnesium L-Threonate-Based Formula Improves Brain Cognitive Functions in Healthy Chinese Adults. Nutrients. 2022.

Frequently Asked Questions

What does magnesium L-threonate support?

Magnesium L-threonate is commonly used in formulations intended to support cognitive function, memory, mental clarity, healthy neurological function, relaxation and healthy sleep-wake cycles.*

What is Magtein®?

Magtein® is a patented magnesium L-threonate ingredient that has been evaluated in human clinical trials examining cognitive performance, memory and sleep-related outcomes.

Has Magtein® been studied in humans?

Yes. Randomized controlled human trials have evaluated Magtein® or magnesium L-threonate-containing formulations for cognition, memory and sleep-related outcomes. The evidence is encouraging but does not establish magnesium L-threonate as a treatment or preventive therapy for neurological disease or sleep disorders.

Does magnesium L-threonate prevent Alzheimer's disease?

No. Magnesium L-threonate has not been proven to prevent, treat or reverse Alzheimer's disease or other forms of dementia.

Is magnesium L-threonate better than magnesium glycinate?

Not universally. Magnesium L-threonate is generally selected when cognitive and brain-focused support is the priority.* Magnesium glycinate is commonly selected for broader magnesium supplementation, relaxation, muscle function and gastrointestinal tolerability.* The appropriate form depends on why magnesium is being used.

Is magnesium L-threonate primarily a sleep supplement?

No. Sleep is one area of study, but magnesium L-threonate is better viewed as a brain-focused magnesium form with research involving cognition, memory, neurological function and sleep-related outcomes. It is not a sedative and should not be expected to treat an underlying sleep disorder.

What flavor is this product?

This version of RetzlerRx® Magnesium L-Threonate Powder is berry flavored. An unflavored version is also available for people who prefer a more neutral powder.

Is the berry version more effective than the unflavored version?

No clinical advantage is claimed for berry flavor. Flavor is primarily a matter of preference and consistency. The reason to choose the berry version is that some people simply prefer drinking a flavored magnesium powder.

How do I take it?

Mix according to the current product label directions or use as directed by your healthcare professional. Follow the current berry product label for serving size and complete mixing instructions.

Can I take it with another magnesium supplement?

Possibly. Using more than one magnesium product increases total supplemental magnesium intake. Diet, kidney function, medications and other supplements should be considered when determining how much supplemental magnesium is appropriate.