Magnesium L-threonate is the only form proven to increase brain magnesium levels. But glycinate is cheaper and better for sleep. Which should you take?
This is one of those topics where the conventional wisdom doesn’t quite hold up.
This is one of those topics where the conventional wisdom doesn’t quite hold up.
The Key Difference: Blood-Brain Barrier
Magnesium threonate (Magtein) was specifically engineered at MIT to cross the blood-brain barrier. A 2010 study in Neuron (Bhatt et al.) showed it increased brain magnesium by 15% while other forms showed no brain uptake. [1]
Related: evidence-based supplement guide
Magnesium glycinate does NOT meaningfully cross the blood-brain barrier. It raises serum magnesium effectively and the glycine component promotes GABA activity (explaining its sleep benefits).
Head-to-Head Comparison
| Factor | Mg Glycinate | Mg L-Threonate |
|---|---|---|
| Brain penetration | Minimal | Proven (15% increase) |
| Sleep quality | Strong evidence | Moderate |
| Cognitive function | No direct evidence | 2 human RCTs positive |
| Anxiety | Good (via glycine/GABA) | Limited data |
| Muscle/cramps | Excellent | Poor (low elemental Mg) |
| Elemental Mg per dose | ~100mg per capsule | ~48mg per capsule |
| Cost (monthly) | $10-15 | $30-45 |
| GI tolerance | Excellent | Excellent |
The Evidence for Threonate
Liu et al. (2022) conducted a 12-week RCT with 109 adults aged 50-70. Threonate group showed significant improvements in working memory, executive function, and processing speed vs placebo. Effect size was moderate (Cohen’s d = 0.45). [3]
When to Choose Each
- Choose Glycinate if: Sleep is your priority, you have muscle cramps, you want general magnesium repletion, or you’re budget-conscious
- Choose Threonate if: Cognitive decline is your concern, you’re 50+, or you want neuroprotective benefits specifically
- Choose Both if: You can afford it — glycinate at night for sleep, threonate in the morning for cognition. No interaction concerns
Ever noticed this pattern in your own life?
Sound familiar?
Dosing Protocol
Glycinate: 200-400mg elemental magnesium, 30 min before bed
I believe this deserves more attention than it gets.
Threonate: 144mg elemental Mg (2g Magtein), split morning and afternoon
Disclaimer: Consult your healthcare provider before starting any supplement, especially if taking medications. [2]
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Last updated: 2026-04-06
Your Next Steps
- Today: Pick one idea from this article and try it before bed tonight.
- This week: Track your results for 5 days — even a simple notes app works.
- Next 30 days: Review what worked, drop what didn’t, and build your personal system.
Disclaimer: This article is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with any questions about a medical condition.
About the Author
Written by the Rational Growth editorial team. Our health and psychology content is informed by peer-reviewed research, clinical guidelines, and real-world experience. We follow strict editorial standards and cite primary sources throughout.
