Magnesium Amounts Used in Sleep Studies (2026)
Not medical advice. This summarizes the placebo-controlled magnesium sleep trials, the NIH limits, the labels manufacturers file with the NIH, and Amazon prices as of the date shown below. Talk to a clinician about sleep problems; ask first if your kidney function is reduced.
Quick answer
Magnesium sleep studies used 250–500 mg of elemental magnesium a night. These are the amounts studied, not recommendations. The newest and largest trial (155 adults, 2025) used 250 mg as magnesium bisglycinate; the older trial in 46 seniors used 500 mg. The NIH limit for magnesium from supplements is 350 mg a day. Ask your clinician about any dose.
Read the Magnesium row on the Supplement Facts panel, not the big number on the front. Of the 833 magnesium labels we read, the median serving is 250 mg but the median day as directed is 399 mg, and 244 labels name oxide (about 4% absorbed) against 94 naming glycinate or bisglycinate. The lowest-cost tablet at 200 mg is Nature Made Magnesium Glycinate 200mg at $0.195 per 200 mg. See the three cheapest per 200 mg →
Want the whole intake picture first, by age and sex? The magnesium dosage guide has the RDA table and the calculator →
On this page
The three cheapest glycinates per 200 mg of elemental magnesium
Product links go to Amazon and we may earn a commission if you buy. It never changes which product we pick or what we say about it. How we choose.
200 mg is the unit used to compare cost here. Some glycinate bottles list a 400 mg serving, which is above the 350 mg NIH supplement limit. Cost per 200 mg is the Amazon pack price we last recorded divided by the total elemental magnesium in the pack, times 200. Cheapest first, from the 6 glycinates we track; the full ranking is on the cheapest glycinate page.
| Product | Per 200 mg | Elemental / serving | Serving | A year at 200 mg | Verification | Buy |
|---|---|---|---|---|---|---|
 BulkSupplements Magnesium Glycinate Powder | $0.117 | 300 mg | 2.2 g powder (3/4 tsp) | $43 | NSF/ANSI 173 (confirmed in registry) | Check price |
 Nature Made Magnesium Glycinate 200mg | $0.195 | 200 mg | 1 capsule | $71 | USP Verified (confirmed in registry) | Check price |
 Vitamin Shoppe Magnesium Glycinate 400 mg | $0.222 | 400 mg (133 mg per tablet) | 3 tablets | $81 | none stated | Check price |
How they compare: Nature Made Magnesium Glycinate 200mg is the cheapest tablet at $0.195 per 200 mg, at 200 mg per tablet. Nature Made Magnesium Glycinate 200mg is USP Verified (confirmed in the USP registry) at $0.195 per 200 mg, 1.0× the price; it is 200 mg a capsule. BulkSupplements Magnesium Glycinate Powder is cheapest of all at $0.117 if you will measure a powder, which is bitter and approximate. A year at 200 mg a day costs $43 to $176 across the 6 glycinates we track.
What the sleep trials actually dosed
Three papers carry the placebo-controlled evidence for magnesium and sleep. Their amounts are listed here as research, not as advice.
250 mg a day, as magnesium bisglycinate, for 4 weeks. The largest trial to date randomised 155 adults aged 18 to 65 who reported poor sleep to 250 mg of elemental magnesium as bisglycinate or placebo. The authors reported a small effect on Insomnia Severity Index scores (Cohen’s d 0.2) (Schuster 2025, PMID 40918053). This amount sits under the 350 mg limit.
500 mg a day for 8 weeks, in older adults. The trial most sleep articles cite randomised 46 people with primary insomnia to 500 mg of magnesium or placebo. Some sleep measures differed from placebo and total sleep time did not reach significance (Abbasi 2012, PMID 23853635). Note the dose: 500 mg is above the NIH supplement limit, taken under trial supervision, in people whose baseline intake was likely low.
Pooled, the results were small. A 2021 meta-analysis found only 3 randomised trials, all in older adults (151 people in total). It reported a small difference in sleep onset latency versus placebo and no statistically significant change in total sleep time; every trial was at moderate-to-high risk of bias and the evidence was graded low to very low (Mah 2021, PMID 33865376).
| Item | Value ( mg) |
|---|---|
| 2025 trial, bisglycinate (n=155) | 250 mg |
| NIH supplement limit | 350 mg |
| 2012 trial, older adults (n=46) | 500 mg |
Nothing between 250 and 500 mg has been tested against placebo for sleep, and the dosage guide explains why the limit and the trial doses disagree.
Which form of magnesium for sleep
Glycinate, also sold as bisglycinate. It is the form the 2025 trial used, it is among the best absorbed, and it is often described as gentler on the stomach. Oxide's fractional absorption has been measured at about 4% in commercial preparations (Firoz 2001, PMID 11794633), so a 400 mg oxide tablet delivers a fraction of the magnesium on its label. Citrate absorbs well and is cheaper, but it has an osmotic (laxative) effect (glycinate vs citrate).
One caution on the glycine argument. Glycine on its own improved subjective sleep in a small placebo-controlled trial, but at 3 g a night (Bannai 2012, PMID 22293292); a 200 mg magnesium glycinate serving carries roughly 1.2 g of glycine at most, since the compound is about 14% magnesium by weight. The glycine in a capsule is far below the amount studied on its own (the arithmetic).
What magnesium labels deliver, and why the front of the bottle misleads
Original research833 magnesium labels retrieved from the NIH Dietary Supplement Label Database on 2026-08-29, out of 39,884 it lists on the market, across 276 brands; 825 carried a parseable elemental dose.
The median label delivers 250 mg of elemental magnesium per serving, and 399 mg a day once you follow its own directions, because 234 of the 826 labels with directions tell you to take more than one serving a day. So a bottle can look like a 250 mg sleep dose on the panel and be a 399 mg day in practice, over the 350 mg limit without you ever deciding to go there. The second thing the shelf tells you is which form it is pushing: oxide appears on 244 labels, glycinate or bisglycinate on 94, so the form the sleep trial used takes more looking for.
| Item | Value ( mg) |
|---|---|
| Median serving | 250 mg |
| NIH supplement limit | 350 mg |
| Median day as directed | 399 mg |
The reading rule: find the Supplement Facts row named Magnesium, the elemental figure the trials and the limit refer to (“magnesium glycinate 1,000 mg” on the front is compound weight, about 140 mg of magnesium), then multiply by the servings a day the directions give. The table above is listed by that row.
How we read the labels
Method: 833 labels retrieved from the NIH Dietary Supplement Label Database (DSLD) v9 on 2026-08-29; 825 carried a parseable elemental dose and 779 also directed a daily amount. The census is the same one behind the dosage guide. What it cannot tell you: how many bottles of each form are sold, or whether a capsule contains what its label says, which is what the USP and NSF marks test.
Reading the label
- Amount: check the Magnesium row on the Supplement Facts panel (elemental magnesium) and how many servings a day the directions give. The NIH limit for supplements is 350 mg a day; the 500 mg trial amount is above it. Ask your clinician about any amount.
- Timing: follow the label; food blunts the loose-stool effect (best time to take magnesium).
- Spacing: 2 hours before or 4 to 6 hours after tetracycline and quinolone antibiotics, and away from large simultaneous calcium doses.
- Talk to a clinician first: anyone with reduced kidney function (eGFR under 60), and anyone with long-lasting sleep problems.
Frequently asked questions
What amounts have magnesium sleep studies used?
The trials used 250 to 500 mg of elemental magnesium a night: 250 mg as bisglycinate in the 155-adult 2025 trial and 500 mg in the 46-person 2012 trial in older adults. These are the amounts studied, not recommendations. The NIH limit for magnesium from supplements is 350 mg a day, and the 500 mg dose was given under trial supervision and is above the limit. Ask your clinician about any dose.
Which form of magnesium has been studied for sleep?
The newest and largest trial used glycinate (bisglycinate), which is among the best absorbed forms. Citrate absorbs well too but has a mild laxative effect; oxide is about 4% absorbed. The glycine it is bound to has its own small sleep evidence at 3 g a day, far more than a magnesium capsule supplies.
Is there an official magnesium dose for sleep?
No. The official numbers are the RDA (320 mg for women, 420 mg for men, from all sources) and the 350 mg supplement limit. The 2025 trial measured its effect at 4 weeks and the 2012 trial at 8. Ask your clinician about any dose.
What did the studies find about magnesium and sleep?
Small and mixed results. Pooling 3 trials in 151 older adults found a small difference in the time to fall asleep versus placebo and no statistically significant difference in total sleep time, and the review graded the evidence low to very low quality. The 2025 bisglycinate trial reported a small effect (Cohen's d 0.2). Talk to a clinician about sleep problems.
Why are some trial amounts above the NIH limit?
500 mg was the dose in the 2012 trial, given under supervision, and it is above the NIH's 350 mg limit for supplemental magnesium. Above the limit the usual result is loose stools. The limit does not apply to magnesium from food, and it matters most if kidney function is reduced. Ask your clinician before taking more than the limit.
Related guides
- Magnesium: what to buy and how much
- Magnesium dosage guide, by age, sex and goal
- Magnesium and sleep
- Best time to take magnesium
- Cheapest magnesium glycinate per 200 mg
- Glycinate vs citrate
- Best magnesium supplement overall
Sources
- Schuster J, Cycelskij I, Lopresti A, Hahn A. “Magnesium Bisglycinate Supplementation in Healthy Adults Reporting Poor Sleep: A Randomized, Placebo-Controlled Trial.” Nat Sci Sleep. 2025. PMID: 40918053
- Abbasi B, et al. “The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial.” J Res Med Sci. 2012. PMID: 23853635
- Mah J, Pitre T. “Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis.” BMC Complement Med Ther. 2021. PMID: 33865376
- Firoz M, Graber M. “Bioavailability of US commercial magnesium preparations.” Magnes Res. 2001. PMID: 11794633
- Bannai M, Kawai N. “New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep.” J Pharmacol Sci. 2012. PMID: 22293292
- NIH Office of Dietary Supplements. Magnesium fact sheet for health professionals. ods.od.nih.gov
- NIH Office of Dietary Supplements. Dietary Supplement Label Database. dsld.od.nih.gov (labels retrieved 2026-08-29).