How much magnesium glycinate can you safely take per day?
The official limit is 350 mg of elemental magnesium per day from supplements, but more recent research suggests that higher doses do not cause diarrhoea in most people. How much magnesium glycinate specifically can be taken safely has not been well studied, so use the 350 mg elemental magnesium figure as your guideline and check your label.
The official safety limit for magnesium supplements is 350 mg per day (elemental magnesium). That limit was established in 1997 based on the risk of diarrhoea. More recent data add nuance to that picture: at doses ranging from 128 to 1200 mg per day, most studies found no significant difference in diarrhoea compared with a placebo. Seven out of ten studies identified found no such difference, and only a minority had participants drop out due to diarrhoea. Researchers therefore argue for a higher limit, but that official revision has not yet taken place.
For magnesium glycinate specifically, safety information is thin. A small 12-week study in healthy older adults found no significant side effects, but that study was small and was primarily designed to measure solubility, not to establish dosing limits. Notably, magnesium glycinate in that study turned out to dissolve less well during digestion than some other forms of magnesium, which may affect actual absorption. What that means in practical terms for how much you absorb cannot be stated with confidence on the basis of these data.
Practically speaking, no specific safety limit has been established for magnesium glycinate as a standalone form. The existing limit of 350 mg elemental magnesium per day applies to all supplement forms combined. Keep in mind that the amount of elemental magnesium in a glycinate capsule is lower than the total weight of the capsule, because the glycinate portion also contributes to that weight. Always check the label for how much elemental magnesium a dose contains, not how much magnesium glycinate is listed.
This answer draws on a broad literature analysis (1997-2022) on magnesium safety, and on one small 12-week randomised study in older adults who used magnesium glycinate as a comparator product. Safety data specific to magnesium glycinate are sparse: no study has investigated dosing limits for this form exclusively. The researchers behind the literature analysis state themselves that the official limit of 350 mg is outdated and should be revised, but that revision has not yet occurred.