The winner isn't who you'd guess
The best value per gram of lab-verified elemental magnesium came from a brand most people have never heard of - not the best seller.
Test results published
Bought at retail, seals documented intact, analysed by ISO 17025 accredited labs. Watch the video for the verdicts - some of these results will surprise you.
On the bench
// Amazon UK's best sellers, bought at retail, one sealed batch each.
What the lab found
The best value per gram of lab-verified elemental magnesium came from a brand most people have never heard of - not the best seller.
Between the best and worst value products, the price per gram of magnesium your body actually gets differs by more than 10x.
Results ranged from 92% to 105% of the label. Which two fell short - and by how much - is in the full breakdown below.
The label trick to watch for
Pure magnesium glycinate is only about 13-14% elemental magnesium. The UK's top magnesium supplier told us levels above 14% are physically impossible - yet some labels imply far more from glycinate alone.
To hit bigger numbers, brands can quietly cut glycinate with magnesium oxide: 63% elemental on paper, but research puts its absorption at roughly 4%, versus 40-50% for glycinate.
The word "(buffered)" - or elemental claims the maths cannot support - usually means oxide is in the capsule, even when it never appears on the ingredients list.
My brand is launching a batch-test system where every batch must pass a 3rd party test before it ships - plus a magnesium supplement dosed with forms your body can actually absorb. No label tricks.
Quick answers
Each product was bought at retail on Amazon UK - two of each. One was shipped to an ISO 17025 accredited lab with the manufacturer's seal documented intact; the backup stays sealed in case a brand disputes the result.
No product was wildly off its elemental magnesium claim - but two came in under their label, and the full claimed-vs-found numbers are in the free results breakdown. The bigger issue was the forms of magnesium used.
It means the glycinate has been diluted with magnesium oxide - a cheaper form that shows a high elemental number on the label but is poorly absorbed by the body. It often is not listed in the ingredients.
For absorption, yes. Research cited in the video puts oxide absorption around 4%, against 40-50% for glycinate. Oxide's big label numbers mostly pass straight through you.
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