The Two Options
Head-to-Head Comparison
| Magnesium L-Threonate | Magnesium Glycinate | |
|---|---|---|
| Crosses blood-brain barrier | Yes (uniquely effective) | Limited (mostly peripheral) |
| Best for | Cognition, memory, brain sleep | Sleep, anxiety, muscles |
| Standard dose | 2 g/day (144 mg elemental) | 200-400 mg elemental |
| Time to effect (cognitive) | 4-12 weeks | Not primary use |
| Time to effect (sleep) | 2-4 weeks | 1-2 weeks |
| GI tolerance | Excellent | Excellent |
| Laxative effect | Minimal | Minimal |
| Cost per month | $30-50 | $10-20 |
| Best timing | Split AM/evening | Evening (with food) |
When to Choose Each
Choose Magnesium L-Threonate when:
- Cognitive function or memory is your specific goal
- You're over 50 with concerns about cognitive aging
- Your sleep issues come with cognitive symptoms (brain fog, mental fatigue)
- You want neuroprotective effects specifically
- Cost isn't a major concern
Choose Magnesium Glycinate when:
- Sleep, anxiety, or muscle relaxation are the goals
- You want general magnesium repletion
- Cost matters (typically 1/3 the price of threonate)
- You're combining with vitamin B6 for PMS support
- You don't need brain-specific effects
Verdict
Frequently Asked Questions
Is magnesium threonate really better for the brain?
Yes, with solid evidence. The Slutsky et al. 2010 Neuron paper demonstrated that L-threonate raises cerebrospinal fluid magnesium 15% in animal models, while seven other tested forms (including glycinate and citrate) did not. The mechanism involves the threonate transporter at the choroid plexus and glucose transporter-mediated CNS delivery. The 2025 Magtein human RCT in adults with self-reported sleep issues showed measurable cognitive and sleep improvements at 2 g/day over 6 weeks. No other magnesium form has demonstrated this brain-specific advantage.
Can I just take more glycinate to get the same brain effect?
No. The blood-brain barrier limitation is structural, not dose-dependent. Higher doses of glycinate raise blood and tissue magnesium more, but brain magnesium stays relatively constant because the BBB tightly regulates magnesium entry. The threonate carrier specifically enables brain penetration in a way more glycinate cannot replicate. If brain magnesium is your specific goal, threonate is the form that achieves it.
Is threonate worth 2-3x the price of glycinate?
Depends on your goal. For cognitive concerns, memory support, or brain-related sleep issues — yes, the brain penetration advantage justifies the cost. For general magnesium repletion, sleep, anxiety, or muscle issues — no, glycinate gives you the same peripheral effects at much lower cost. The honest framing: threonate is for specific brain goals, not a "premium" general magnesium.
Can I take threonate and glycinate together?
Yes, and many people do for combined effects. Common protocol: threonate 1-2 g during the day for cognitive support, glycinate 200-400 mg at bedtime for sleep. Total elemental magnesium across both should stay under 400-500 mg/day for most adults to avoid GI effects (though both forms are well-tolerated). The combination addresses both brain and peripheral magnesium needs.
Why is the threonate dose so much higher (2 g vs 400 mg)?
Because threonate has lower elemental magnesium content per gram. 2 g of magnesium L-threonate provides only ~144 mg of elemental magnesium (the rest is the threonate carrier). Compare to 2 g of magnesium glycinate which provides ~280 mg elemental. The threonate carrier itself is the active component for brain delivery, not the elemental magnesium total. So the comparison isn't apples-to-apples — threonate is more about delivery mechanism than total magnesium dose.
Which is better for sleep specifically?
Depends on the type of sleep issue. For racing thoughts, mental fatigue, or sleep with cognitive components — threonate may work better because it addresses brain magnesium. For muscle tension, restless legs, or general anxiety-related sleep issues — glycinate works better through peripheral nervous system effects. The 2025 Magtein RCT showed sleep improvements; multiple studies show glycinate helps sleep too. For most people without specific cognitive concerns, glycinate at bedtime is the more cost-effective choice.