Two bottles, both labelled 1000 mg
A 1000 mg tablet of magnesium glycinate carries about 141 mg of the mineral itself. The same 1000 mg of magnesium oxide carries roughly 603 mg, because magnesium is 60.3% of that compound by weight. Amino acid chelates hold far less, with taurate down at 8.9% and L-threonate at 8.3%, and that gap exists before absorption enters the conversation at all.
So the front of the bottle is a packaging decision, not a nutritional one. What you're buying is the elemental figure, the fraction that is the mineral and nothing else. Everything around it is carrier, and the carrier is not filler in a bad sense. Glycine and taurine are molecules with their own behaviour, but they are not magnesium.
Why chelation is not the same as better absorption
Chelation means the mineral is bound to an organic molecule, usually an amino acid, rather than sitting as an inorganic salt. Ligands like glycine and taurine are large, so they drag the elemental percentage down. They also change how the compound behaves in the gut, which is the part that actually gets discussed in marketing copy.
The NIH lists magnesium aspartate, citrate, lactate and chloride among the forms more easily absorbed by the body [1]. Oxide is not on that list. Published estimates put oxide absorption as low as 4% of the elemental fraction, and a 2025 trial in 155 adults with poor sleep used 250 mg of the mineral from bisglycinate [2][3]. One trial, one modest result. Absorption is one factor among several, and it sits next to dose, meal composition and your own gut rather than above them.
Which form tends to sit better with your stomach
Tolerance is individual, and we won't pretend otherwise. Oxide is the form most often linked with loose stools and digestive complaints, largely because a large amount arrives in the gut at once and draws water with it. Citrate does something similar at higher doses. Glycinate has the reputation of being the gentler option, and while that reputation runs slightly ahead of the head-to-head evidence, it is a reasonable place to start if you've had trouble before.
If you're taking 400 mg from oxide and your stomach objects, dropping to 200 mg and splitting the dose across two meals is a cheaper experiment than switching forms.
Cheaper still, eat more of it. One ounce of dry roasted almonds gives 80 mg. Half a cup of cooked black beans gives 60 mg, and a cup of cooked spinach lands near 78 mg. Food magnesium comes with fibre and protein attached, and it never provokes the gut the way a concentrated tablet can.
How to compare two labels in under a minute
Find the Supplement Facts panel and look for the word elemental. A line reading "Magnesium (as magnesium glycinate) 100 mg" states 100 mg of the mineral. A line reading "Magnesium glycinate 1000 mg" states the compound weight, which works out at about 141 mg. Same bottle, two very different numbers, and only one of them answers your question.
Then check the figure against your target. Adults need 400 mg to 420 mg a day from all sources if they're men, or 310 mg to 320 mg if they're women. Food supplies part of that. The tolerable upper limit of 350 mg applies to supplemental magnesium only, and it exists because of the gut rather than because the mineral is dangerous at ordinary intakes [1].
Two capsules of a 500 mg glycinate product might give you 140 mg. Two capsules of a 500 mg oxide product might give you 300 mg, and cost a third as much. Whether the second is better for you depends entirely on how your gut responds, and no label can tell you that.
Where our own capsule lands
Our product is a fully reacted chelate, and we print the elemental figure on the panel instead of burying it behind the compound weight. That makes the arithmetic visible and makes us easy to compare against anything else on the shelf. Judge us on the elemental figure and the form, and nothing else.
If you want 400 mg in a single daily capsule, ours is not the answer, and an oxide tablet will get you there for less money. If you want 100 mg to 150 mg that you'll actually keep taking every night for weeks, the trade looks different.
References
[1] National Institutes of Health, Office of Dietary Supplements. Magnesium fact sheet for health professionals. [2] Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research, 2001. [3] Randomised placebo-controlled trial of magnesium bisglycinate, 250 mg elemental, in adults reporting poor sleep. 2025.
Frequently asked questions
What is a chelated mineral?Show answerHide answer
A mineral bound to an organic molecule - an amino acid or an organic acid - rather than left as an inorganic salt.
Does chelation guarantee better absorption?Show answerHide answer
No. It is one factor among several, including dose and what else is in the meal.
Which form is easiest on the stomach?Show answerHide answer
Tolerance is individual. Oxide is the form most often associated with digestive complaints.
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.
