Magnesium Glycinate vs. Citrate vs. Threonate
Three forms of magnesium, three different jobs. Picking the wrong one is why your $40 supplement isn't doing anything.
Magnesium is the second most common nutrient deficiency in U.S. adults after Vitamin D. The textbook says 320–420 mg/day from the RDA. Most adults get 60–70% of that. Chronic sub-optimal magnesium status is associated with poor sleep, muscle cramps, anxiety, migraines, and elevated blood pressure.
So supplementation makes sense for most people. The question is which form.
Magnesium isn't one thing. The form determines where it actually goes.
**Magnesium glycinate** is magnesium bound to glycine — a calming amino acid. Highly bioavailable, gentle on the gut, and useful for sleep and anxiety. The glycine itself contributes to the sedative effect. If you're taking magnesium at bedtime for sleep, this is the form.
**Magnesium citrate** is bound to citric acid. More laxative effect — at higher doses it's literally used as a bowel prep. For most people that's a downside, but for those with chronic constipation it's a feature, not a bug. Decent bioavailability, cheaper than glycinate.
**Magnesium L-threonate** is the only form shown to meaningfully cross the blood-brain barrier and raise CSF magnesium levels. The cognitive and memory effects in animal studies are striking; human data is thinner but suggestive. Used specifically for cognitive support, not sleep.
Magnesium oxide and citrate make up the majority of cheap drugstore multivitamin magnesium — both are poorly absorbed relative to the chelated forms. For IV protocols (Myers' Cocktail, Magnesium Drip), magnesium chloride or sulfate is used because it goes directly into circulation, sidestepping the absorption question entirely.
Buy what matches your purpose: glycinate for sleep, citrate for regularity, threonate for cognition.
