Magnesium glycinate vs threonate: when each makes sense

Magnesium is the most over-recommended supplement on the internet. The question isn''t whether to take it - most adults run mild deficiencies - it''s which form, at what dose, for what outcome. Glycinate and threonate are the two we stock; here''s the decision tree.

Magnesium glycinate

Chelated with the amino acid glycine. High bioavailability (~80% absorbed). Calming, sleep-supporting, well-tolerated even at higher doses. Take it for: sleep onset, muscle relaxation, anxiety reduction, general magnesium repletion. Standard dose: 200-400mg elemental, 30-60 minutes before bed.

Magnesium L-threonate (Magtein)

The only form that meaningfully crosses the blood-brain barrier. Bioavailability for systemic magnesium is moderate, but the cognitive marker uptake is the highest of any form studied. Take it for: cognitive support, memory consolidation, age-related cognitive decline prevention. Standard dose: 1,000-2,000mg of the threonate (which delivers ~144-288mg elemental magnesium).

What we''d skip

Magnesium oxide is the cheapest form and the one most commonly found in mass-market multivitamins. Absorption is around 4%. If a product just says "magnesium" without specifying the form, assume oxide and assume you''re mostly buying laxative.

Stacking

You can stack glycinate (PM, for sleep) with threonate (AM or split, for cognitive support). Total elemental magnesium should stay under ~500mg/day from supplements unless you have a confirmed clinical deficiency. Excess is excreted, but high doses can cause GI distress.