Magnesium is one of the few supplements where a real deficiency is statistically common — roughly a third of adults in Central Europe don't hit the recommended intake. The form you pick decides whether your supplement does anything.
The four main forms
Glycinate: bound to the amino acid glycine, well tolerated, mildly calming. First pick if you dose in the evening or sleep quality matters.
Citrate: bound to citric acid, high bioavailability, mildly laxative. Useful if you're prone to constipation, less ideal before training.
Threonate: the only form that meaningfully crosses the blood-brain barrier. Studies suggest cognitive effects but are small and largely manufacturer-funded.
Oxide: the cheapest and worst. Bioavailability below 4%. Sits in almost every drugstore effervescent — a major reason "magnesium did nothing for me" is true so often.
Our recommendation
For 90% of readers: 300 mg of elemental magnesium as glycinate in the evening. Reliable levels, well tolerated, under 20 cents a day. Use threonate only if cognition is explicitly the goal.
