Stool form and regularity

Nature Made Magnesium Oxide 250 mg

The form of magnesium the constipation trials used, sold as a plain 250 mg tablet.

Format: Tablet, once a day
Type: Magnesium
Cost: $0.04 a day
Customer rating: 4.7 out of 5 from 34,996 ratings from Amazon

What customers consistently report

Reliable, predictable bowel movements for people who take it for that
Better sleep and fewer night cramps, the reasons most buyers give
A low price for a long supply

Those are the themes that recur across the reviews. High review confidence — 4.7 from 34,996 Amazon ratings across the tablet sizes.

Why it might work

Magnesium oxide is poorly absorbed, and what stays in the bowel draws water into it osmotically, softening stool and speeding transit. That poor absorption is the point for constipation: more of the dose remains in the gut to do the job, which is why the trials used oxide rather than the better-absorbed citrate. Effect is usually within a day. The same mechanism causes diarrhea if the dose is too high, and the mineral that is absorbed has to be cleared by the kidneys.

What the research supports

Form-specific evidence at a higher dose than the label. A randomized, double-blind, placebo-controlled trial gave 1.5 g of magnesium oxide a day for 28 days to women with chronic constipation: overall symptoms improved in 70.6% against 25.0% on placebo, with more spontaneous bowel movements and a shorter colonic transit time (33 analyzed). A 2021 three-arm trial in 90 patients found 68.3% improved on the same dose against 11.7% on placebo. The 2023 AGA/ACG guideline gives magnesium oxide a conditional recommendation. No trial of this brand was found.

What the label discloses

Magnesium oxide supplying 250 mg of elemental magnesium per tablet, with cellulose, croscarmellose, stearic acid and a coating; no added sugar. Nature Made states USP verification on this product line, which is an independent check of identity and potency. The label carries a kidney-disease caution.

Who this tends to suit

We match this product to people reporting constipation, irregular bowel habits and a feeling of incomplete emptying. It fits someone whose priority is regularity or a steady daily routine. Whether it is the best fit for you depends on the rest of your answers — what you have already tried, what format you will take, and anything that has to be ruled out.

Where it may not fit

The label supports gluten-free, no added sweeteners and minimal ingredient list. We flag this product for anyone taking prescription medication, and the quiz removes it rather than recommending it in those cases. That is a caution about who should be deciding, not a claim about the product. A tablet only works if you will take it once a day, every day.

Side effects and what to be aware of

The label dose is one tablet (250 mg) a day and is sold for muscle and nerve support; the constipation trials used 1.5 g a day of magnesium oxide, about 900 mg of elemental magnesium or roughly three and a half of these tablets, and that is a dose to discuss with a doctor rather than copy from a website. Too much causes diarrhea. Anyone with kidney disease should not take magnesium for this without advice, because the kidneys clear it. The label says consult a physician if you take any medication, and it should be spaced from some antibiotics and other drugs.

Before you take this. Speak to a doctor or pharmacist first if you are taking prescription medication. Nothing on this page is medical advice, and no supplement diagnoses, treats, cures or prevents disease.

Buy it at iHerb

Is this the right one for you?

The quiz works out which of the products we have researched fits your symptoms, your routine and what you have already tried — and tells you plainly if none of them do.

Take the quiz →

Free. Private. Nothing to sign up for.