Magnesium threonate and magnesium glycinate are both well-absorbed forms of magnesium, but they’re not competing for the same job. Threonate is specifically researched for cognitive function and brain health. Glycinate is the more versatile daily supplement — better absorbed than most forms, gentle on the gut, and significantly cheaper.
For most UK adults looking to support sleep, reduce muscle tension, or address general magnesium deficiency, glycinate is the more practical choice. Here’s what the research actually shows for each.
What Is Magnesium Threonate?
Magnesium threonate (often sold as Magtein, the patented form) is magnesium bound to threonic acid, a metabolite of vitamin C. It was developed specifically to cross the blood-brain barrier more effectively than other magnesium forms.
A 2010 study published in Neuron (Slutsky et al.) found that raising brain magnesium levels using magnesium-L-threonate improved synaptic density and memory performance in animal models. A 2016 clinical trial (Liu et al., Journal of Alzheimer’s Disease) found it may support cognitive performance in older adults with mild cognitive impairment.
The research is promising but limited. Most trials are small, short-term, and funded by parties with commercial interests in Magtein. It’s a genuinely interesting compound, not hype, but it’s not yet proven to a standard you’d compare with, say, the sleep evidence for glycinate.
What Is Magnesium Glycinate?
Magnesium glycinate is magnesium chelated to glycine, an amino acid. Chelation significantly improves absorption in the small intestine compared to inorganic forms like oxide or carbonate. For more on how chelation works, see our guide to chelated magnesium.
Glycine itself has calming properties — it modulates GABA receptors and supports sleep onset by reducing core body temperature. That makes glycinate useful beyond just correcting a magnesium deficiency.
It’s also one of the gentlest forms on the digestive system, which matters if you’ve had problems with oxide or citrate supplements causing loose stools.
How They Compare
| Feature | Magnesium Threonate | Magnesium Glycinate |
|---|---|---|
| Primary research area | Cognitive function, memory | Sleep, anxiety, general deficiency |
| Blood-brain barrier penetration | Higher (by design) | Standard |
| Elemental magnesium per dose | Lower (~7% of compound weight) | Higher (~11% of compound weight) |
| Gut tolerance | Good | Excellent |
| Evidence base | Promising but limited | Stronger for sleep and relaxation |
| Typical monthly cost (UK) | £30–£60+ | £10–£20 |
Dosing: What You’re Actually Getting
One thing most comparison articles gloss over is how much elemental magnesium you’re actually absorbing from each form.
Threonate delivers roughly 7% of its weight as elemental magnesium in practice. A typical daily dose of 1.5–2g of magnesium threonate provides only around 145mg of actual magnesium. The rest is threonic acid, which is the part doing the brain-specific work.
Glycinate (bisglycinate) delivers around 11% elemental magnesium by weight in practice. But the real advantage is absorption efficiency. Because the magnesium is chelated to glycine, it’s taken up through amino acid transport pathways in the gut rather than competing with other minerals for absorption. You get more from less.
The NHS doesn’t set a specific RDA for magnesium, but most adults in the UK need somewhere between 270mg and 400mg daily from all sources combined (food and supplements). If you’re already eating a reasonable diet, you don’t necessarily need to hit the upper end of that range through supplementation alone.
Magnesium Glycinate vs Threonate for Anxiety
This is one of the most common questions in this comparison, and the answer is fairly clear: glycinate is the better-supported option for anxiety.
Magnesium plays a direct role in regulating the hypothalamic-pituitary-adrenal (HPA) axis, your body’s central stress response system. Low magnesium levels are associated with increased cortisol output and heightened stress reactivity. Correcting a deficiency can help restore normal stress signalling.
With glycinate, you get a second mechanism: glycine is an inhibitory neurotransmitter that acts on GABA receptors. That’s the same pathway targeted by anti-anxiety medications, though the effect from supplemental glycine is much milder.
Threonate’s research focuses almost entirely on cognitive outcomes — memory, executive function, synaptic plasticity. There’s no meaningful clinical data on its effects on anxiety specifically. If anxiety or stress management is your primary reason for supplementing, glycinate is the more evidence-based choice.
Side Effects and Gut Tolerance
Both forms are well tolerated, but they differ in one practical way: the laxative threshold.
All magnesium forms can cause loose stools at high doses. The threshold depends on how much unabsorbed magnesium reaches the colon. Poorly absorbed forms like magnesium oxide hit that threshold quickly. Glycinate, because it’s absorbed through a different pathway, is one of the least likely forms to cause digestive issues.
Threonate is also generally well tolerated, though some users report drowsiness or headaches at higher doses. Because the elemental magnesium content is low, gut issues are uncommon.
Neither form has significant safety concerns at standard doses. If you’re taking other medications or have kidney problems, check with your GP before starting any magnesium supplement.
When Threonate Makes Sense
If your primary concern is cognitive performance — memory, focus, mental clarity — and you’re willing to pay a significant premium for a compound with early but specific brain-targeted research, threonate is worth considering.
It may also be relevant if you’re looking for a form that specifically raises cerebrospinal fluid magnesium levels, which standard supplementation does less effectively.
That said, be realistic about what the evidence currently supports. The 2016 Liu trial showed modest improvements in a specific cognitive test battery over 12 weeks. That’s encouraging but not a dramatic cognitive upgrade — and most participants in that trial had baseline cognitive impairment.
When Glycinate Makes More Sense
For most people over 40 taking magnesium to support sleep quality, reduce muscle tension, ease anxiety, or simply address dietary shortfall, glycinate is the better starting point. The evidence for magnesium and sleep is more established, and glycinate’s glycine component adds a second mechanism of action.
A 2021 systematic review in BMC Complementary Medicine and Therapies (Mah & Pitre) found oral magnesium supplementation was associated with improved sleep efficiency and sleep onset time in older adults. Much of that research used glycinate or similar bioavailable forms.
Glycinate also costs 2–4 times less than threonate for equivalent elemental magnesium. If cognitive support is a secondary goal rather than your primary reason for supplementing, that cost difference is hard to justify.
For a detailed look at how magnesium works for sleep specifically, see our post on magnesium for sleep.
Can You Take Magnesium Glycinate and Threonate Together?
Yes. There’s no interaction between the two forms, and some people do take both — glycinate in the evening for sleep and relaxation, threonate earlier in the day for cognitive support.
If you go this route, keep track of your total elemental magnesium intake from all sources. The upper supplemental limit generally cited is around 400mg of elemental magnesium per day. Going above that doesn’t cause serious harm in healthy adults, but it increases the chance of digestive discomfort.
For most people, starting with glycinate alone makes more sense. It covers the broadest range of benefits at the lowest cost. You can always add threonate later if cognitive support is a specific priority.
The Bottom Line
Neither form is universally better — they serve different purposes. Threonate is a specialist tool for people with a specific interest in brain magnesium levels. Glycinate is the more practical, better-evidenced daily supplement for sleep, recovery, anxiety, and general health.
If you’re not sure where to start, glycinate is the sensible default. Our Magnesium Glycinate is a vegan-certified pure bisglycinate chelate — no oxide blending, no fillers — providing 55mg elemental magnesium per capsule for efficient absorption.
FAQ
Q: Is magnesium glycinate or threonate better for sleep?
A: Glycinate has the stronger evidence base for sleep. Both the magnesium content and the glycine component support sleep quality — glycine helps lower core body temperature and modulate GABA, which are key to sleep onset. Threonate’s research focuses primarily on cognition, not sleep.
Q: Is magnesium threonate worth the extra cost?
A: Possibly, if your primary goal is cognitive support and you’re prepared to take it consistently for at least 12 weeks. For general magnesium supplementation, sleep, or gut-friendly daily use, glycinate offers better value without a meaningful trade-off in benefit.
Q: Can I take magnesium glycinate and threonate together?
A: Yes — there’s no interaction between them. Some people take glycinate in the evening for sleep and threonate in the morning for cognitive support. Just monitor your total elemental magnesium intake and stay at or below roughly 400mg per day from supplements to avoid digestive discomfort.
Q: Which form of magnesium is best for anxiety?
A: Glycinate is most commonly used for anxiety support. Glycine’s inhibitory neurotransmitter activity and magnesium’s role in regulating the stress response both contribute. Research on threonate for anxiety is limited.
Q: What is magnesium threonate used for?
A: Magnesium threonate (Magtein) is primarily researched for its ability to raise magnesium levels in the brain. Early human trials suggest it may support memory and cognitive function, particularly in older adults with mild cognitive decline.
Q: Is magnesium glycinate suitable for vegans?
A: Magnesium glycinate itself is typically vegan — it’s a mineral chelated to an amino acid (glycine), with no animal-derived ingredients. However, capsule materials vary by brand. Our Magnesium Glycinate is certified vegan.
References
- Slutsky I, et al. (2010). Enhancement of learning and memory by elevating brain magnesium. Neuron, 65(2), 165–177.
- Liu G, et al. (2016). Efficacy and safety of MMFS-01 for treating cognitive impairment in older adults. Journal of Alzheimer’s Disease, 49(4), 971–990.
- Mah J & Pitre T. (2021). Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies, 21, 125.
- Coudray C, et al. (2005). Study of magnesium bioavailability from ten organic and inorganic Mg salts. Magnesium Research, 18(4), 215–223.
- NHS. Vitamins and minerals — Magnesium.
This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting any supplement, especially if you are pregnant, have a medical condition, or take prescription medication.
