Does magnesium oxide make you poop?
Yes, at laxative doses. Magnesium oxide is the form doctors use for constipation, and it beat a placebo in trials. One everyday tablet is a smaller push. Pick yours:
MAYBE, especially if you take more than one.
Oxide is about 60% magnesium by weight, so one 500 mg tablet is roughly 300 mg, close to the 350 mg limit. It absorbs poorly, and what stays in the gut pulls water with it.
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 oxide make you go?
The meter says what should happen. Your bowels get a vote too.
Why it works
It barely absorbs, so it stays in the gut
Oxide is one of the least absorbed forms of magnesium. NIH lists it among the forms most often reported to cause diarrhea, because the leftover magnesium holds water in the bowel.
It beat placebo
In a small trial of people with chronic constipation, about 71% improved on magnesium oxide against 25% on a placebo.
Gut doctors recommend it
The 2023 US constipation guideline from the two main gastroenterology societies suggests magnesium oxide for chronic constipation, alongside fiber and senna.
Sources: Mori, Tack & Suzuki, Nutrients 2021 (review); AGA-ACG constipation guideline 2023; NIH Office of Dietary Supplements, Magnesium fact sheet.