Magnesium

What are magnesium's main benefits?

Updated 10 Nov 2026

Short answer

Taken by mouth, magnesium has the best evidence for four uses:

  • Constipation. In 2 trials of magnesium oxide, 68% of adults with chronic constipation improved, against 19% in the control groups.[1]
  • Blood pressure. A 2025 review of 38 trials found 2.81 mmHg lower systolic and 2.05 mmHg lower diastolic blood pressure. The drop was larger in people with high blood pressure who took blood pressure medicines, and not significant in people with normal blood pressure.[2]
  • Migraine. US neurology and headache societies rate magnesium as probably effective for preventing migraine.[3] A 2025 review found 1.66 fewer migraine days a month.[4]
  • Blood sugar. In people with diabetes or at high risk of it, magnesium lowered fasting blood sugar in a 2021 review.[5] A 2026 review found a small effect: fasting glucose 3.60 mg/dL lower and HbA1c 0.15 percentage points lower.[6]

Other expected benefits have weak support. For sleep, a 2026 review of 12 trials found inconsistent results with low to very low certainty.[7] A Cochrane review found magnesium unlikely to prevent leg cramps in older adults.[8] In athletes, a review found no gain in muscle strength or power.[9]

Many large magnesium trials tested it as a hospital medicine, not as a supplement. Magnesium sulphate lowered the risk of eclampsia (seizures) by 58% in 10,141 women with pre-eclampsia.[10] An infusion during heart surgery gave fewer heart attacks and rhythm problems in 250 patients with a thickened heart wall.[11] A magnesium sulphate drink cleaned the bowel before colonoscopy as well as the standard solution in 1,174 older adults.[12]

Sources (12)

  1. 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
  2. Magnesium Supplementation and Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Argeros Z, Xu X, Bhandari B, Harris K, Touyz RM, Schutte AE Hypertension, 2025. PMID 41000008
  3. Evidence-based guideline update: NSAIDs and other complementary treatments for episodic migraine prevention in adults: report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society. Holland S, Silberstein SD, Freitag F, Dodick DW, Argoff C, Ashman E Neurology, 2012. PMID 22529203
  4. Effects of selected dietary supplements on migraine prophylaxis: A systematic review and dose-response meta-analysis of randomized controlled trials. Talandashti MK, Shahinfar H, Delgarm P, Jazayeri S Neurol Sci, 2025. PMID 39404918
  5. Oral Magnesium Supplementation for Treating Glucose Metabolism Parameters in People with or at Risk of Diabetes: A Systematic Review and Meta-Analysis of Double-Blind Randomized Controlled Trials. Veronese N, Dominguez LJ, Pizzol D, Demurtas J, Smith L, Barbagallo M Nutrients, 2021. PMID 34836329
  6. Comprehensive Effects of Magnesium Supplementation on Cardiometabolic Risk Factors: A Systematic Review and Dose-Response Meta-Analysis. Mohammadi S, Palermo A, Ojani P, Alaghemand N, Pirayvatlou PS, Mirkarimi M, et al. Nutrients, 2026. PMID 42588058
  7. Magnesium Supplementation for Sleep in Adults: A Systematic Review of Randomized Controlled Trials. Lopresti AL, Smith SJ, Drummond PD J Diet Suppl, 2026. PMID 42661485
  8. Magnesium for skeletal muscle cramps. Garrison SR, Korownyk CS, Kolber MR, Allan GM, Musini VM, Sekhon RK, et al. Cochrane Database Syst Rev, 2020. PMID 32956536
  9. The effect of magnesium supplementation on muscle fitness: a meta-analysis and systematic review. Wang R, Chen C, Liu W, Zhou T, Xun P, He K, et al. Magnes Res, 2017. PMID 29637897
  10. Do women with pre-eclampsia, and their babies, benefit from magnesium sulphate? The Magpie Trial: a randomised placebo-controlled trial. Altman D, Carroli G, Duley L, Farrell B, Moodley J, Neilson J, et al. Lancet, 2002. PMID 12057549
  11. The perioperative effect of magnesium sulfate in patients with concentric left ventricular hypertrophy undergoing cardiac surgery: A double-blinded randomized study. Soliman R, Abukhudair W Ann Card Anaesth, 2019. PMID 31274484
  12. Low-dose of magnesium sulfate solution was not inferior to standard regime of polyethylene glycol for bowel preparation in elderly patients: a randomized, controlled study. Ge F, Kang X, Wang Z, Zhu H, Liao L, Wang M, et al. Scand J Gastroenterol, 2023. PMID 35920250

More about magnesium

What is magnesium?Which foods are good sources of magnesium?What does elemental magnesium mean on a supplement label?Who is most likely to have low magnesium?Is magnesium safe?Does magnesium help you sleep?

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