Does magnesium make you poop?
Depends which one, and how much. The laxative bottle is built to, and works within hours. A glycinate capsule barely touches you. Pick yours:
YES, that's its job.
The label says it usually works in 30 minutes to 6 hours. Half a bottle (5 fl oz) carries about 1,400 mg of magnesium: four times the daily supplement limit, on purpose.
How much magnesium is in one dose
Daily limit from supplements: 350 mg (NIH)
The black line is the 350 mg daily supplement limit. Amounts are elemental magnesium, the number the limit counts.
Did magnesium make you go?
The meter says what should happen. Your bowels get a vote too.
Why it works
It pulls water into your gut
Magnesium your body doesn't absorb stays in the bowel and holds water there. More water means softer, faster stool. That's exactly how the laxative bottle works.
The form changes everything
Some forms dissolve and absorb well (citrate, chloride, lactate); others, like oxide, absorb poorly and hang around in the gut. Forms also differ in how much magnesium they actually carry per milligram.
Past 350 mg, expect the runs
NIH puts the daily limit for magnesium from supplements and medicines at 350 mg for adults. Go well over it and diarrhea, nausea and cramps are the usual result. Magnesium from food doesn't count toward it.
Sources: NIH Office of Dietary Supplements, Magnesium fact sheet; MedlinePlus, Magnesium citrate; Magnesium citrate oral solution, Drug Facts label.