Magnesium glycinate vs citrate
Choose magnesium citrate when you want the form with a published absorption edge and you can tolerate looser stools. Choose magnesium glycinate when citrate or oxide bothers your stomach. Neither form is proven better for sleep in a head-to-head trial. Oxide is the one that is absorbed poorly. Count elemental magnesium, not the weight of the salt.
These two salts solve different complaints. Magnesium citrate pulls water into the gut. Magnesium glycinate is the chelate people switch to when they want less of that effect.
Absorption
A randomized comparison found citrate more bioavailable than other common magnesium preparations (PMID 14596323). Tests of US commercial products put oxide at the low end of absorption (PMID 11794633). A later review of intestinal absorption reaches the same practical conclusion: the compound on the label changes the dose you actually take up (PMID 29123461).
Sleep and constipation are different jobs
If the goal is sleep, read best magnesium for sleep. The short version is that glycinate won the marketing, not a head-to-head sleep trial. If the goal is constipation, citrate is the form that matches that effect, and the dose should stay in a range you can live with. Kidney disease is a reason to ask before either one.
Certified bottles, where a public list actually named them, are in certified magnesium products compared.
Sources
- Walker AF, et al. Mg citrate found more bioavailable than other Mg preparations. Magnes Res. 2003. PMID: 14596323.
- Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res. 2001. PMID: 11794633.
- Schuchardt JP, Hahn A. Intestinal absorption and factors influencing bioavailability of magnesium — an update. Curr Nutr Food Sci. 2017. PMID: 29123461.