Magnesium Glycinate 400 mg: What a Serving Really Delivers
Not medical advice. This is label arithmetic against the NIH intake limits and the labels manufacturers file with the NIH, plus Amazon prices as of the date shown below. Talk to a clinician before starting magnesium, especially if your kidney function is reduced; it can interact with some antibiotics and bisphosphonates.
Quick answer
“400 mg magnesium glycinate” is two different doses depending on which number the label means. If the Supplement Facts row that says Magnesium reads 400 mg, you get 400 mg of magnesium, which is 50 mg above the NIH’s 350 mg limit for magnesium from supplements. If the 400 mg is the weight of the compound, you get about 56 mg of magnesium, because bisglycinate is only 14.1% magnesium. Of the 57 labels named glycinate that we read, the median serving delivers 220 mg and 36.8% deliver 400 mg or more.
Read the panel row, then buy by cost per milligram. The cheapest 400 mg of elemental magnesium as glycinate we track is BulkSupplements Magnesium Glycinate Powder at $0.234; the cheapest in a capsule or tablet is Nutricost Magnesium Glycinate 210 mg at $0.348. See every glycinate ranked per 400 mg →
Every magnesium glycinate we track, ranked by cost per 400 mg of 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.
The dose column is the Supplement Facts magnesium row (elemental), never the compound weight; cost per 400 mg is the pack price divided by the total elemental magnesium in the bottle, times 400. “Units per 400 mg” is how many capsules or tablets it takes. Cheapest first; prices are the Amazon price we last recorded for the exact pack (see the date below).
| Product | Per 400 mg | Mg per serving | Per unit | Units per 400 mg | Days at 400 mg | Price | Verification | Buy |
|---|---|---|---|---|---|---|---|---|
 BulkSupplements Magnesium Glycinate Powder | $0.234 | 300 mg / 2.2 g powder (3/4 tsp) | scoop | measure | 85 | $19.97 | NSF/ANSI 173 (confirmed in registry) | Check price |
 NOW Magnesium Bisglycinate Powder | $0.301 | 250 mg / 1 level teaspoon (~2.9 g) | scoop | measure | 48 | $14.69 | listing says NPA GMP Certified, Non-GMO Project Verified; we did not find it in a public registry | Check price |
 Nutricost Magnesium Glycinate 210 mg | $0.348 | 210 mg / 3 capsules | 70 mg | 6 | 63 | $21.95 | none stated | Check price |
 Nature Made Magnesium Glycinate 200mg | $0.390 | 200 mg / 1 capsule | 200 mg | 2 | 30 | $11.70 | USP Verified (confirmed in registry) | Check price |
 NOW Magnesium Glycinate 200 mg | $0.435 | 200 mg / 2 tablets | 100 mg | 4 | 60 | $26.12 | listing says NPA GMP Certified; we did not find it in a public registry | Check price |
 Vitamin Shoppe Magnesium Glycinate 400 mg | $0.443 | 400 mg / 3 tablets | 133 mg | 4 | 45 | $19.94 | none stated | Check price |
 Nature's Bounty High Absorption Magnesium Glycinate 240 mg | $0.444 | 240 mg / 2 capsules | 120 mg | 4 | 36 | $15.97 | none stated | Check price |
 Doctor's Best High Absorption Magnesium | $0.466 | 200 mg / 2 tablets | 100 mg | 4 | 30 | $13.99 | none stated | Check price |
 KAL Magnesium Glycinate 350 mg | $0.472 | 350 mg / 4 VegCaps | scoop | – | 52 | $24.79 | none stated | Check price |
 Thorne Magnesium Glycinate | $0.963 | 120 mg / 1 capsule | 120 mg | 4 | 27 | $26.00 | NSF/ANSI 173 (confirmed in registry) | Check price |
The spread is $0.234 to $0.963 per 400 mg, 4.1× from cheapest to priciest, for the same element in the same salt. 1 of the 10 products print 400 mg as the serving, and each of those is a multi-tablet serving, not one; 1 of the 10 show a USP mark on the listing; the verification column shows which we confirmed in a public registry. The powders win on price because you are not paying for capsules, and lose on precision because a level teaspoon is a rough dose.
The two 400s: compound weight versus elemental magnesium
Magnesium glycinate (bisglycinate) is one magnesium atom bonded to two glycine molecules. By molar mass, magnesium is 14.1% of the compound, so a capsule holding 400 mg of magnesium bisglycinate contains about 56 mg of magnesium, and a serving that delivers 400 mg of magnesium has to contain about 2,840 mg of the compound, which is why 400 mg elemental servings are two or three large tablets or a heaped scoop of powder. Both numbers are honest; the problem is that the front of the bottle can print either one, and “magnesium glycinate 400 mg” sounds identical whichever it means.
The label row settles it. On a US Supplement Facts panel the row named Magnesium is elemental by regulation, whatever the source in parentheses says; that row is what the RDA (320 mg for women, 420 mg for men, from all sources) and the 350 mg supplemental upper limit refer to. A front label that says 400 mg next to a panel that says magnesium 56 mg is describing the compound; a panel that says magnesium 400 mg (as bisglycinate) is describing the dose. Our dosage guide covers the same distinction for citrate and oxide, and the cheapest glycinate page ranks the same products per 200 mg.
Is 400 mg of magnesium the right dose?
400 mg of elemental magnesium is above the supplement limit. The NIH sets 350 mg a day as the tolerable upper level for magnesium from supplements specifically (food magnesium does not count against it), because above that loose stools become common in healthy adults. The trials of magnesium used 200 to 400 mg a day, and the sleep trials in older adults used 320 to 500 mg (Mah 2021, PMID 33865376). These are amounts studied, not recommendations. Ask your clinician before taking more than the limit. Two smaller servings with food are usually easier on the gut than one large one, and the absorbed fraction falls as the dose rises.
Glycinate is priced for tolerability, not for a special dose. In a crossover trial, isotope-labelled magnesium diglycinate was absorbed better than magnesium oxide (Schuette 1994, PMID 7815675). In 46 healthy adults taking 300 mg a day for 60 days, the organic forms were absorbed better than oxide, which did not differ from placebo (Walker 2003, PMID 14596323), and a 2021 systematic review of bioavailability trials reached the same ranking, organic salts above the inorganic ones (Pardo 2021, PMID 34111673). None of those trials was run at 400 mg of glycinate, so the honest claim is that magnesium as glycinate is better absorbed than magnesium as oxide.
This page is for readers checking what a “400 mg” label means. Ask your clinician before taking more than 350 mg, and ask first if your kidney function is reduced, since magnesium clears slowly. A bottle whose front says 400 mg of the compound gives about 56 mg of magnesium.
We read 57 glycinate labels: 400 mg is the top quarter of the shelf, not the middle
Original research827 magnesium labels retrieved from the NIH Dietary Supplement Label Database on 2026-08-27; 57 whose product name says glycinate or bisglycinate, from 38 brands, were read for the elemental magnesium row, units per serving and other magnesium forms, and 149 with a glycinate row anywhere on the panel were read the same way. Every figure below was recomputed in two halves of the corpus and only the ones that agreed are printed.
Among the 57 labels named glycinate, the median serving delivers 220 mg of magnesium, the 75th percentile is 400 mg, and 36.8% deliver 400 mg or more. The median capsule or tablet carries 100 mg, so a 400 mg dose is typically 4 units, and 19.3% of labels named glycinate also carry another magnesium form on the panel, usually oxide or malate, which means the glycinate share of the dose is smaller than the name suggests. Across the wider set of 149 labels with a glycinate row, the median serving is 250 mg, the lower quartile 200 mg, 78.5% deliver at least 200 mg, 32.9% at least 400 mg, and 78.5% need two or more units for one serving. A serving of 400 mg is the top quarter of the glycinate shelf; the typical bottle is built around 200 to 250.
| Item | Value ( mg) |
|---|---|
| Median per unit | 100 mg |
| Median per serving | 220 mg |
| 75th percentile serving | 400 mg |
| Supplement upper limit | 350 mg |
How we read the labels
Method: 827 labels retrieved from the NIH Dietary Supplement Label Database on 2026-08-27; 57 labels named glycinate or bisglycinate were analysed (labels sold as magnesium whose product name says glycinate or bisglycinate; Supplement Facts magnesium row is elemental mg per serving; per unit = per serving / units per serving), plus 149 labels with a glycinate row anywhere on the panel. The 102 labels the broader magnesium census classifies as glycinate by primary form (median 232.5 mg per serving) are a descriptive count from a separate read and not a validated finding. The census is published as open data at /magnesium/glycinate-400-mg.json (CC BY 4.0). What it cannot tell you: sales volume per label, whether a product contains what its label says (that is what USP marks are for), or anything about products that have not filed with the NIH.
Magnesium glycinate products compared per 400 mg
Want a one-capsule serving? The best glycinate guide ranks by form and verification, and the sleep research guide lists the amounts used in trials.
Frequently asked questions
Does "400 mg magnesium glycinate" mean 400 mg of magnesium?
Only if the Supplement Facts row that says Magnesium reads 400 mg. Magnesium bisglycinate is about 14.1% magnesium by weight, so 400 mg of the compound carries roughly 56 mg of magnesium, and 400 mg of elemental magnesium takes about 2,840 mg of the compound. The front of the bottle can print either number. The panel row is the one the RDA (320 mg women, 420 mg men) and the 350 mg supplement limit refer to.
Is 400 mg of magnesium glycinate too much?
400 mg of elemental magnesium from a supplement is 50 mg above the NIH's 350 mg upper limit for supplemental magnesium, the level above which loose stools become common in healthy adults. It is inside the 200 to 400 mg range the trials used. Ask your clinician before taking more than the limit, especially if your kidney function is reduced. 400 mg of the compound (about 56 mg of magnesium) is well below the limit.
How many capsules is 400 mg of magnesium glycinate?
Among the 57 labels named glycinate we read, the median capsule or tablet carries 100 mg of elemental magnesium, so 400 mg is typically 4 units. In our catalog it runs from 2 to 6 capsules or tablets depending on the product, and the powders measure it as a scoop or teaspoon. A bottle that says 400 mg per serving usually means two tablets, not one.
What is the cheapest magnesium glycinate per 400 mg?
BulkSupplements Magnesium Glycinate Powder at $0.234 per 400 mg of elemental magnesium, a powder you measure with a teaspoon. The cheapest capsule or tablet is Nutricost Magnesium Glycinate 210 mg at $0.348. The priciest, Thorne Magnesium Glycinate, costs 4.1 times as much for the same elemental dose. Price per bottle tells you nothing until you divide by the magnesium in it.
Does glycinate absorb better than other forms at 400 mg?
Better than oxide, on the trials that compared them: organic forms were absorbed better than oxide, which did not differ from placebo in healthy adults. No trial shows glycinate beating citrate, and none was run at exactly 400 mg. The absorbed fraction falls as the dose rises.
Related guides
- Magnesium: what to buy and how much
- Magnesium dosage guide
- Cheapest magnesium glycinate per 200 mg
- Best magnesium glycinate
- Glycinate vs citrate
- Best magnesium supplement, ranked
- Magnesium side effects
Sources
- Schuette SA, Lashner BA, Janghorbani M. “Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection.” JPEN J Parenter Enteral Nutr. 1994. PMID: 7815675
- Walker AF, et al. “Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study.” Magnes Res. 2003. PMID: 14596323
- Pardo MR, et al. “Bioavailability of magnesium food supplements: A systematic review.” Nutrition. 2021. PMID: 34111673
- Mah J, Pitre T. “Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis.” BMC Complement Med Ther. 2021. PMID: 33865376
- NIH Office of Dietary Supplements. “Magnesium Fact Sheet for Health Professionals.” ods.od.nih.gov (RDA and the 350 mg supplemental upper limit).
- NIH Office of Dietary Supplements. Dietary Supplement Label Database. dsld.od.nih.gov (labels retrieved 2026-08-27).