Guide
What is magnesium glycinate? A plain guide
Magnesium glycinate is magnesium bound to glycine, and the magnesium is only 11-14% of the compound's weight. Here's what it is, what elemental magnesium means, and what's actually established about it.
Magnesium glycinate is magnesium bound to two molecules of the amino acid glycine, sold as a supplement because it dissolves easily and is generally well tolerated. Its formula is C4H8MgN2O4, and magnesium is only about 11–14% of that compound's weight — the rest is glycine. What it does in the body is what magnesium does; the glycine is the delivery vehicle, not a separate benefit.
What magnesium glycinate actually is
Chemically, it's a chelate: one magnesium ion held by two glycinate molecules, molecular weight 172.42 g/mol (PubChem CID 84645). Manufacturers also sell hydrated or "buffered" versions that mix in a cheaper compound such as magnesium oxide, which changes the elemental percentage without necessarily changing the label's description. That's why the number worth checking on any bottle isn't the compound weight in big letters on the front — it's the elemental magnesium figure in the Supplement Facts panel.
Elemental magnesium: the number that actually counts
"Elemental" means the weight of the magnesium atom itself, separate from what it's bound to. Pure magnesium glycinate is a ceiling of about 14.1% magnesium by weight (24.3 g of magnesium's atomic weight ÷ 172.42 g/mol). A label at or under that ratio is consistent with being glycinate alone; a label well above it is getting some of its magnesium from something else.
| Figure | Amount | % of compound |
|---|---|---|
| Magnesium glycinate (compound) | 2,500 mg | 100% |
| Elemental magnesium (from that compound) | 275 mg | 11.0% |
| Theoretical ceiling for pure glycinate | — | ~14.1% |
A label that only prints the compound weight, with no elemental figure, is not telling you how much magnesium you're actually taking. Ours prints both.
What magnesium glycinate is typically used for
Magnesium itself contributes to normal muscle function, to normal energy-yielding metabolism (including the reduction of tiredness and fatigue), to normal nervous system and psychological function, and to electrolyte balance. Those are established nutrient roles, and they apply to magnesium generally, not to the glycinate form specifically.
What the category markets glycinate for — sleep, and better absorption or gentler digestion than other forms — is a separate question from what magnesium itself does, and the evidence for those two specific claims is weak. We go through the sleep literature in detail, including the trial closest to a glycinate dose, in magnesium glycinate and sleep: what the evidence actually shows. Short version: the broadest recent review rated the evidence low to very low certainty, and it does not support magnesium as a routine sleep treatment.
How it compares to other forms
No form of magnesium has been shown, in a well-powered trial in healthy adults, to be reliably better absorbed than the others. Glycinate has never beaten citrate: a 60-day trial in 46 healthy adults found citrate produced the highest blood magnesium of the forms tested, with an amino-acid chelate not outperforming it. A 2024 crossover study saw plasma magnesium rise after citrate and oxide but not after bisglycinate. A 2017 review of the absorption literature concludes the type of magnesium salt matters less than is often assumed — dose and a person's existing magnesium status matter more.
We lay out the full comparison, form by form, in types of magnesium compared. Each pairing also gets its own page: glycinate vs citrate, glycinate vs oxide, glycinate vs malate, glycinate vs L-threonate, glycinate vs taurate, glycinate vs chloride, gluconate, sulfate and orotate, and plain magnesium vs magnesium glycinate.
Dose and safety, briefly
Adults should generally keep magnesium from supplements under 350 mg a day; that upper limit is set at the level where loose stools become more likely, and it doesn't count magnesium already in food. A 2023 review of the underlying diarrhea data argued the limit may be conservative, finding no significant difference in diarrhea across most of the studies it examined at intakes of 128–1,200 mg a day. Our three-capsule serving delivers 275 mg of elemental magnesium, under the 350 mg mark. If you have kidney disease, are pregnant or nursing, or take prescription medication, ask your doctor before adding any magnesium supplement.
Questions people ask
What is magnesium glycinate good for?
The magnesium in it contributes to normal muscle function, normal energy-yielding metabolism, normal nervous system function and electrolyte balance. It is not shown to be better absorbed, gentler, or a sleep aid compared with other forms — those are separate, weaker claims worth checking before you buy on them.
What does magnesium glycinate do for the body?
It supplies elemental magnesium, which the body uses in hundreds of enzyme reactions, including those involved in muscle contraction, energy production and nerve signaling. The glycine component doesn't add a documented benefit beyond making the compound easy to formulate into a capsule.
What is the difference between magnesium glycinate and magnesium citrate?
Citrate is bound to citric acid rather than glycine, carries a higher elemental percentage (roughly 16% by weight), and is the only form with a positive human bioavailability trial against oxide in healthy adults. See magnesium glycinate vs citrate for the full comparison.
What is the difference between magnesium oxide and magnesium glycinate?
Oxide has the highest elemental percentage of any common form, around 60%, but the lowest measured absorption in the trials that have tested it. Glycinate has a lower elemental percentage and no proven absorption advantage over oxide in the whole-group results of the one direct human comparison. Details in magnesium glycinate vs oxide.
What is chelated magnesium glycinate?
"Chelated" describes the same thing as "glycinate": magnesium held by an organic molecule (here, glycine) rather than existing as a simple salt like oxide or chloride. "Chelated magnesium glycinate" is a redundant but common label phrase, not a different or superior product.
What is the best time to take magnesium glycinate?
There's no trial establishing an optimal time of day for magnesium glycinate specifically. The sleep trial closest to our dose (250 mg of bisglycinate) had participants take it before bed, but that was the study's protocol, not a demonstrated timing advantage — its own results were mostly null on secondary sleep measures.
What does magnesium glycinate help with?
The claims the evidence supports are about magnesium's general nutrient roles, not glycinate specifically: muscle function, energy metabolism and reduced tiredness, nervous system function, and electrolyte balance. Broader claims — sleep, cramps, anxiety — are not supported at typical supplement doses; see the linked evidence review for the sleep literature in detail.
Sources
- Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study In 46 healthy adults taking 300 mg a day for 60 days, citrate raised blood magnesium most; an amino-acid chelate did not beat it.
- Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection In 12 people after bowel surgery, one 100 mg dose of glycinate was absorbed about the same as oxide overall.
- Comparative Clinical Study on Magnesium Absorption and Side Effects After Oral Intake of Microencapsulated Magnesium (MAGSHAPE(TM) Microcapsules) Versus Other Magnesium Sources In 40 healthy adults given one dose, blood magnesium rose after citrate and oxide but not significantly after bisglycinate.
- Intestinal Absorption and Factors Influencing Bioavailability of Magnesium-An Update A 2017 review of magnesium absorption research concluded the type of magnesium salt matters less than is often claimed — the evidence for one form being reliably better absorbed than another is inconsistent.
- Perspective: Call for Re-evaluation of the Tolerable Upper Intake Level for Magnesium Supplementation in Adults In 7 of 10 trials between 128 and 1,200 mg a day, magnesium caused no more diarrhea than the comparison.
*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.
