Magnesium labels compete on percent. Oxide often wins that contest and loses the one that matters, which is how much you absorb and whether it loosens your stools. Glycinate is the form most often discussed for sleep and for people who want a gentler stomach. Citrate is the form people reach for when constipation is the reason they are looking. Threonate appears in smaller studies around the brain and sleep, and that evidence is still limited.
This picker asks what you are comparing forms for, then names one form to read about. It does not return milligrams. A useful amount depends on diet, kidney function, and medicines such as levothyroxine, certain antibiotics, and bisphosphonates, which magnesium can bind if you take them at the same time.
Food magnesium and a capsule are different decisions. If a blood test or a clinician already set a target, follow that. The glycinate guide linked below is the place to see what sleep studies actually support.
The picker maps a goal to the form most often discussed for that job. Glycinate comes up for sleep and for people who want a gentler stomach. Citrate comes up when constipation is the reason. Oxide contains more elemental magnesium per gram but is absorbed poorly and upsets some stomachs. Threonate has small studies around brain and sleep, and the evidence is still limited.
This does not choose a dose, test your blood level, or clear an interaction with levothyroxine, antibiotics, or bisphosphonates. Magnesium from food and from a capsule are not the same decision.
Glycinate is the form most often discussed for sleep in consumer guides, and threonate appears in smaller studies. Neither is a sleep medicine. The linked glycinate article covers what the evidence does and does not show.
Oxide looks strong on a label because more of the powder is magnesium, but less of it is absorbed, and it is more likely to loosen stools. Percent on the label is not the same as what you absorb.
No. A useful dose depends on diet, kidney function, and medicines. Take that question to a clinician or a registered dietitian.