About 70 mg, if the product is pure magnesium bisglycinate. Bisglycinate is 14.1% magnesium by weight at most, so 500 mg of the compound supplies at most 70.5 mg of elemental magnesium.
Commercial grades that hold water assay lower, roughly 11 to 13%, which works out to 55 to 65 mg. If a label claims substantially more than 70 mg from 500 mg, the product is drawing magnesium from a second, denser source as well.
Why 14.1% is a ceiling rather than a grade
Magnesium glycinate is magnesium bonded to two glycine molecules, written Mg(C2H4NO2)2. Its molar mass is 172.42 g/mol. Magnesium itself weighs 24.305 g/mol. Divide one by the other and you get 14.10%.
That fraction is fixed by the molecule. No manufacturer can raise it, no purity grade exceeds it, and no lot of genuine bisglycinate will ever test above it. Glycine is simply heavy, and you swallow two of them for every magnesium ion you absorb.
This is why magnesium glycinate capsules tend to be large, and why a meaningful daily dose often needs two of them.
Worked figures for common label weights
| Compound on the label | At 14.1% | At 12% |
|---|---|---|
| 250 mg | 35 mg | 30 mg |
| 500 mg | 70 mg | 60 mg |
| 550 mg | 78 mg | 66 mg |
| 800 mg | 113 mg | 96 mg |
| 1000 mg | 141 mg | 120 mg |
| 2000 mg | 282 mg | 240 mg |
What it means if your label says more
Suppose a jar states 500 mg of magnesium glycinate providing 110 mg of elemental magnesium. That is 22%, well above the ceiling. The arithmetic is telling you something real: the capsule contains magnesium from another compound, most often magnesium oxide, which is about 60% magnesium by weight and therefore lifts the average.
The trade calls this a buffered or blended grade. It is a normal ingredient sold by major chelate manufacturers, and it is permitted in India, the European Union, Canada and the United States. A blend is not a defect.
What matters is whether the label admits it. If the front of the jar says 100% chelated and the ingredient list names only one magnesium source, the arithmetic and the claim contradict each other. Undeclared blending is the thing worth objecting to, and it has triggered a recall in Canada and class action settlements in the United States.
Check any label in ten seconds. Our magnesium label calculator takes the compound weight and the elemental figure from any jar, works out the percentage, and tells you whether that number is possible for a single ingredient or only for a blend.
How to find the right number on the pack
- Find the compound weight. This is the large number on the front, such as "Magnesium Glycinate 500 mg". It is the weight of the whole compound, glycine included.
- Find the elemental magnesium. Look in the nutritional information panel for a line reading "elemental magnesium" or "providing X mg magnesium". This is the only figure your body acts on.
- Divide the second by the first. Multiply by 100 for the percentage, then compare it against 14.1%.
If a product states only the compound weight and never gives an elemental figure, treat that as a reason to look elsewhere. You cannot dose what the label will not tell you.
How much do you actually need?
The ICMR-NIN (2020) recommended dietary allowance for magnesium is 440 mg a day for adult men and 370 mg for adult women, counting food as well as supplements. Most people get a reasonable share from dal, leafy vegetables, nuts and whole grains, so a supplement is usually closing a gap rather than supplying the whole requirement.
A common supplemental range is 100 to 300 mg of elemental magnesium a day. The tolerable upper intake level for supplemental magnesium is 350 mg a day for adults, and magnesium from food does not count toward it. Absorption also falls as the dose rises, so splitting an amount across the day absorbs a greater share of it than one large dose.
Related reading: 22% vs 14% magnesium glycinate, and what the percentage actually means. Is buffered magnesium glycinate bad?
This article is educational and is not medical advice. Magnesium supplements are not intended to diagnose, treat, cure or prevent any disease. Consult a qualified healthcare professional before starting any supplement, particularly if you are pregnant, breastfeeding, have kidney disease, or take prescription medicines. Percentages are calculated from standard atomic weights; commercial lots vary with moisture content.