Magnesium Forms Compared for Sleep: Bisglycinate vs Citrate vs Oxide vs Threonate

Verdict: For nightly sleep use, magnesium bisglycinate is the best-balanced choice across absorption, tolerability, and sleep relevance. Citrate is well absorbed but has a laxative tendency that makes it less comfortable at bedtime, L-threonate is promising for brain-related outcomes but expensive and so far studied mainly in industry-funded trials, and oxide is cheap but poorly absorbed. The form matters more than the headline milligrams, because a high dose of a poorly absorbed form delivers very little usable magnesium.

Comparison at a glance

Form	Absorption	Tolerability	Sleep relevance	Elemental magnesium (approx.)	Best use
Bisglycinate (glycinate)	Good (amino acid chelate)	Gentle, minimal laxative effect	Form used in the most recent sleep RCT	~14% (varies by chelate grade)	Nightly sleep support
Citrate	Good	Mild laxative effect at higher doses	Indirect, via general magnesium status	~16%	Digestion, general top-up
Oxide	Poor (about 4% fractional absorption)	Laxative at higher doses	Weak, little usable magnesium delivered	~60% (but mostly unabsorbed)	Budget products, occasional constipation
L-threonate	Designed for brain bioavailability	Generally well tolerated	Improved subjective and objective sleep in one industry-funded RCT	~8%	Cognitive or brain-focused goals, premium price

Lunia Restore uses Magnesium Bisglycinate at 500 mg of the compound, which provides 90 mg of elemental magnesium. That is below the elemental dose used in the main bisglycinate sleep trial (250 mg), so it is best understood as a calming top-up within a stack rather than a standalone high-dose magnesium product. That is stated plainly rather than glossed over.

The elemental magnesium math

Every magnesium supplement is magnesium bound to a carrier molecule, and only part of the listed weight is actual (elemental) magnesium. The percentage of elemental magnesium is set by chemistry, by the weight of the magnesium relative to the weight of its carrier. As a rough guide, magnesium oxide is around 60% elemental by weight, citrate around 16%, bisglycinate around 14% (higher in some commercial chelate grades), and L-threonate around 8%. So a label showing 500 mg of a compound is not promising 500 mg of magnesium. A 500 mg bisglycinate dose, for example, delivers somewhere in the range of 70 to 90 mg of elemental magnesium depending on the chelate.

The twist is that the form with the most elemental magnesium on paper, oxide, is the one your body absorbs least. A study of US commercial preparations found magnesium oxide had only about 4% fractional absorption, far below organic forms (Firoz and Graber, 2001). A randomized, double-blind trial similarly found that organic forms, citrate and an amino acid chelate, were absorbed significantly better than oxide (Walker et al., 2003). So oxide's high elemental percentage is misleading: a lot of magnesium on the label, very little making it into the body.

The reasoning

For sleep, bisglycinate is the best-balanced pick because it combines good absorption with gentle tolerability and is the form behind the most relevant recent evidence. A 2025 randomized, double-blind, placebo-controlled trial found magnesium bisglycinate produced a modest but significant improvement in insomnia severity over four weeks (Schuster et al., 2025), and a meta-analysis of oral magnesium for insomnia in older adults found possible benefit while noting the underlying trials are mixed in quality (Mah and Pitre, 2021). The amino acid chelate also tends to sit easier in the gut than citrate.

Citrate is well absorbed and a reasonable everyday magnesium source, but its osmotic, mildly laxative effect (the same property that makes it useful for constipation) is the catch at bedtime. Oxide is the budget default and packs a lot of magnesium by weight, but its poor absorption means most of it is not used, which makes it the least efficient choice for raising magnesium status. L-threonate is the interesting newcomer for sleep because it is designed to be brain bioavailable, and a randomized controlled trial reported improvements in both subjective and objective sleep, though that study was industry funded and threonate products are more expensive (Hausenblas et al., 2024). For a nightly sleep supplement at a sensible price, bisglycinate remains the default, with threonate as a premium alternative for those prioritizing cognitive angles.

Frequently asked questions

What is the best form of magnesium for sleep?

Magnesium bisglycinate (often labeled glycinate) is generally the best form for sleep. It is well absorbed, gentle on the stomach without the laxative pull of citrate, and it is the form used in the most relevant recent sleep research. L-threonate is a reasonable premium alternative, while oxide is the least suitable because it is poorly absorbed.

Why is magnesium oxide so cheap if it does not absorb well?

Magnesium oxide is inexpensive to produce and contains a high percentage of elemental magnesium by weight, so a brand can print a large number on the label cheaply. The problem is that only about 4% of it is actually absorbed, so much of that headline number passes through unused. Better absorbed forms like bisglycinate cost more to make.

How much elemental magnesium does a 500 mg dose provide?

It depends entirely on the form, because elemental magnesium is only a fraction of the compound weight. A 500 mg dose of bisglycinate provides roughly 70 to 90 mg of elemental magnesium, while 500 mg of oxide would list far more elemental magnesium on paper but deliver very little once poor absorption is accounted for. Always read the elemental figure, not just the compound weight.

Is magnesium citrate or glycinate better for sleep?

For sleep specifically, glycinate (bisglycinate) is usually the better choice. Both are well absorbed, but citrate has a mild laxative effect at the doses needed to support magnesium status, which can be uncomfortable at bedtime. Citrate is a better pick when digestion is the main goal.

Is magnesium L-threonate worth it for sleep?

L-threonate is designed to be brain bioavailable and showed improvements in sleep quality in a randomized controlled trial, so it is a credible option, especially if cognitive benefits are also a priority. The caveats are that the supporting trial was industry funded, its elemental magnesium content is low, and it is typically more expensive than bisglycinate.

Sources

1. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research. 2001;14(4):257-262. PubMed: 11794633
2. Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research. 2003;16(3):183-191. PubMed: 14596323
3. Schuster J, et al. Magnesium Bisglycinate Supplementation in Healthy Adults Reporting Poor Sleep: A Randomized, Placebo-Controlled Trial. Nature and Science of Sleep. 2025;17:2027-2040. PubMed Central: PMC12412596
4. Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a Systematic Review and Meta-Analysis. BMC Complementary Medicine and Therapies. 2021;21:125. PubMed Central: PMC8053283
5. 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;8:100121. Sleep Med X, 2024; doi:10.1016/j.sleepx.2024.100121

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.