Magnesium

Is magnesium used for constipation?

Updated 10 Nov 2026

Short answer

Yes. Magnesium is a main ingredient of some laxatives, such as milk of magnesia.[1] Magnesium salts that the gut does not absorb hold water in the bowel by osmosis and loosen stools.[1]

A 2023 review pooled 2 trials of magnesium oxide in adults with chronic constipation. 68% improved on magnesium oxide, against 19% in the control groups. People had 3.72 more bowel movements a week, and softer stools.[2] In a 2021 trial in 90 adults, one group took 1.5 g of magnesium oxide a day for 28 days. 68.3% of them improved, about as many as with senna (69.2%), against 11.7% with placebo.[3]

A 2023 guideline of two US gastroenterology societies gives magnesium oxide a conditional recommendation for chronic constipation. Polyethylene glycol and some other medicines got a strong recommendation.[4]

Laxative doses can be well above the US upper limit of 350 mg a day, but part of the magnesium is not absorbed.[1] People with kidney disease can build up too much magnesium and should ask a doctor first.[1]

Sources (4)

  1. Magnesium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  2. The effect of food, vitamin, or mineral supplements on chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials. van der Schoot A, Creedon A, Whelan K, Dimidi E Neurogastroenterol Motil, 2023. PMID 37243443
  3. Senna Versus Magnesium Oxide for the Treatment of Chronic Constipation: A Randomized, Placebo-Controlled Trial. Morishita D, Tomita T, Mori S, Kimura T, Oshima T, Fukui H, et al. Am J Gastroenterol, 2021. PMID 32969946
  4. American Gastroenterological Association-American College of Gastroenterology Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation. Chang L, Chey WD, Imdad A, Almario CV, Bharucha AE, Diem S, et al. Gastroenterology, 2023. PMID 37211380

More about magnesium

What is magnesium?Which foods are good sources of magnesium?What does elemental magnesium mean on a supplement label?What are magnesium's main benefits?Who is most likely to have low magnesium?Is magnesium safe?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.