Magnesium for sleep is one of the most-searched supplement questions there is — and most of what gets written about it doesn't cite an actual trial. Here's one, published in 2026.
The trial
155 healthy adults reporting poor sleep took 250mg of elemental magnesium (as bisglycinate) plus 1,523mg of glycine nightly, or a placebo, for four weeks, in a randomized, placebo-controlled design.
The result
The primary outcome — Insomnia Severity Index — improved significantly more on magnesium: a 28% reduction from baseline, versus 18% on placebo. That's a real, statistically significant difference.
Why magnesium and glycine are plausible candidates
Neither ingredient was picked at random. Magnesium is a cofactor the nervous system leans on to keep itself from over-firing. A 2025 mechanistic review in Nature and Science of Sleep lays out two specific pathways: magnesium potentiates GABA-A receptor activity, which is the brain's main inhibitory signaling system and the same receptor family targeted by prescription sedatives, and it acts as a voltage-dependent blocker of NMDA receptors, damping the excitatory glutamate signaling that can keep a wired brain from downshifting at night.2 Put simply: more GABA-A activity and less NMDA activity both point the nervous system toward calm, which is the physiological state sleep onset requires.
Glycine has its own, separate line of human evidence — it isn't just riding along with magnesium in this trial. In a randomized, double-blind, cross-over study, adults with sleep complaints who took glycine before bed reported better subjective sleep quality, and the improvement correlated with actual polysomnographic changes in their recorded sleep architecture, not just self-report.3 A related trial from the same research group found glycine improved next-day performance and reduced fatigue in people who were deliberately sleep-restricted.4 One proposed mechanism is that glycine helps lower core body temperature around bedtime, which is itself part of the body's natural sleep-onset signal.
Because this trial dosed magnesium and glycine together, it cannot tell you how much of the 28% improvement came from the magnesium alone.
That's the honest limitation worth stating plainly. This was a combination-product trial, not a head-to-head test of magnesium versus glycine versus both together. The two ingredients have different, independently-supported mechanisms, which makes it plausible they're additive — but this specific dataset can't isolate each one's individual contribution to the 28% figure.
The honest size of the effect
The effect size was small (Cohen's d = 0.2). Secondary measures — daytime sleepiness, fatigue, mood — showed no significant difference between groups. This is a real, modest effect on one specific measure (insomnia severity), not evidence of a broader transformation in how people felt during the day.
Is this result typical, or an outlier?
It's worth checking this trial against the wider magnesium-and-sleep literature, since a single combination-product study sitting on its own is easy to either oversell or dismiss. A separate, earlier randomized, double-blind, placebo-controlled trial gave 46 elderly adults with primary insomnia 500mg of magnesium daily — no glycine — for eight weeks. It also found a statistically significant improvement in Insomnia Severity Index score (p = 0.006), along with improved sleep time, sleep efficiency, and sleep onset latency, plus favorable shifts in serum melatonin and cortisol.5 The population, dose, and duration all differ from the 2026 trial, so the two aren't directly comparable — but the direction and general modesty of the effect line up. That's a reasonable degree of consistency across two independent trials using different magnesium protocols in different populations, which is more reassuring than either result would be alone.
Why the form of magnesium matters
The 2026 trial used magnesium bisglycinate, and that choice isn't incidental. Magnesium salts differ substantially in how well they're absorbed and how well people tolerate them. A controlled comparison of magnesium citrate against magnesium oxide — one of the cheapest and most common forms on supplement shelves — found citrate produced a meaningfully larger rise in urinary magnesium excretion after dosing, a marker of how much was actually absorbed, while oxide performed poorly by comparison.6 Magnesium bound to glycine (bisglycinate, sometimes called glycinate) is generally reported to behave similarly to citrate on absorption, with the added practical advantage that it tends to cause less of the loose-stool, GI-upset effect that unabsorbed magnesium salts like oxide are known for — because more of the mineral is taken up in the small intestine rather than pulling water into the colon. This matters for a sleep supplement specifically: a form that causes GI discomfort before bed works against the goal, regardless of what's happening at the GABA-A receptor.
What this means in practice
If someone's main complaint is difficulty falling or staying asleep, this trial is a reasonable evidence basis for magnesium bisglycinate at this dose. If the goal is more energy or a better mood during the day, this particular trial doesn't support that — a different mechanism, or a different intervention, would be doing that work. And because the trial tested magnesium and glycine together, someone taking magnesium bisglycinate alone, without an added glycine dose, is working from a related but not identical evidence base — the mechanistic case for magnesium's own contribution is real, but the 28% figure specifically describes the combination, not magnesium in isolation.
What we take from this
We dose magnesium (glycinate form) in the range this and other sleep-focused trials tested. We describe the effect the way the trial describes it: real, modest, and specific to insomnia severity — not a cure for poor sleep. We also think it's worth being direct about what our own product does and doesn't replicate: Proco's Magnesium Glycinate is dosed at 275mg elemental magnesium and third-party tested every batch, which sits close to the elemental magnesium dose used in this trial — but it does not include the 1,523mg glycine dose the trial paired it with. Someone wanting to approximate this specific protocol would be adding a separate glycine source; we're not claiming our single-ingredient product reproduces the exact combination result above, and we'd rather say that plainly than let the citation imply more than it does.
This article is for informational purposes only and has not been evaluated by the FDA. It is not intended to diagnose, treat, cure, or prevent any disease, including insomnia. Speak with a healthcare provider before starting any new supplement, especially if you take medication or have an existing health condition.
References
- Nature and Science of Sleep / Dove Press (2026). Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. dovepress.com/magnesium-bisglycinate-supplementation-in-healthy-adults-reporting
- He C, Wang B, Chen X, Xu J, Yang Y, Yuan M (2025). The Mechanisms of Magnesium in Sleep Disorders. Nature and Science of Sleep. dovepress.com/the-mechanisms-of-magnesium-in-sleep-disorders
- Yamadera W, Inagawa K, et al. (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms. onlinelibrary.wiley.com/doi/10.1111/j.1479-8425.2007.00262.x
- Bannai M, Kawai N, Ono K, Nakahara K, Murakami N (2012). The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Frontiers in Neurology. pubmed.ncbi.nlm.nih.gov/22529837
- Abbasi B, Kimiagar M, Sadeghniiat K, Shirazi MM, Hedayati M, Rashidkhani B (2012). The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences. pubmed.ncbi.nlm.nih.gov/23853635
- Lindberg JS, Zobitz MM, Poindexter JR, Pak CY (1990). Magnesium bioavailability from magnesium citrate and magnesium oxide. Journal of the American College of Nutrition. pubmed.ncbi.nlm.nih.gov/2407766
Related reading
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- What the Research Actually Says About Nutrition and Attention
Proco Magnesium Glycinate is dosed at 275mg elemental magnesium, third-party tested every batch. Shop Magnesium →