Independent supplement ratingsUS and Canada · Updated weekly
A ratings desk for a category that has spent thirty years grading its own homework.
A ratings desk for a category that has spent thirty years grading its own homework.
Magnesium L-threonate is sold almost entirely on a cognitive angle — the idea that it crosses into the brain better than other forms. That story rests largely on animal research; the human evidence for memory or cognition is limited and early, not settled.
It's also a low-elemental form: the big milligram number on the tub is mostly the threonate carrier, so the actual magnesium dose is smaller than it looks, at a much higher price per milligram.
If your goal is general magnesium sufficiency, glycinate or citrate do it for far less. Threonate is a speculative buy for the brain claim specifically — pay attention to the elemental figure before you decide it's worth the premium. Research on PubMed →
Glycinate, unless you are specifically buying the brain claim and accept the evidence is thin. L-threonate is marketed on the argument that it raises magnesium in the central nervous system, and the human research behind that is limited. It is also the weakest form by arithmetic: a 2,000 mg dose of the compound delivers only around 144 mg of elemental magnesium, against 200 mg or more from a smaller, cheaper glycinate capsule.
The same as magnesium generally, and generally milder because the elemental dose is low: loose stools and stomach upset are the common ones, and they arrive faster the more unabsorbed magnesium reaches the bowel. Some users report drowsiness, which is unsurprising given it is usually taken in the evening. Anyone with reduced kidney function should not supplement magnesium without medical advice.
For most people, no. It is several times the price per gram of elemental magnesium of the well-absorbed alternatives, for a benefit that rests on a small human evidence base. If your goal is meeting your daily magnesium target, a cheaper form does it better. That is why it carries a C on our evidence scale rather than an A.
Reviewed by the NFS editorial team · Educational only — not medical advice.