Magnesium citrate
Magnesium citrate is safe for most adults with healthy kidneys and has moderate evidence for preventing migraine at about 600 mg of magnesium a day; it is also sold over the counter as a saline laxative for occasional constipation, although we found no trial of the citrate form itself for that use. Its sleep evidence is weak: in the one citrate trial, sleep improved just as much on placebo.
The main caution is kidney disease, because magnesium can build up to harmful levels, and a single laxative dose holds far more magnesium than the daily upper limits for supplements.
At a glance
Last reviewed 10 October 2026What it's used for
Evidence is rated per use. The same ingredient can be strong for one thing and traditional for another.
| Use | Evidence | What the research shows |
|---|---|---|
| Migraine preventionCompare remedies for headaches → | Moderate | In a 12-week placebo-controlled trial of 81 adults with migraine, 600 mg (24 mmol) magnesium a day as trimagnesium dicitrate cut attack frequency by 41.6% in weeks 9 to 12, against 15.8% on placebo; 18.6% of those on magnesium had diarrhoea. A 2018 systematic review of five trials rated magnesium 'possibly effective' (grade C), with one of its two highest-quality trials positive, and named 600 mg magnesium dicitrate as a safe, low-cost option.1,2 |
| Occasional constipation (laxative)Compare remedies for digestion → | Limited | Magnesium citrate oral solution is sold over the counter in the US as a saline laxative; the label says it generally produces a bowel movement in half an hour to 6 hours. A 2021 systematic review graded magnesium-containing laxatives as moderate evidence and described citrate as more strongly osmotic than hydroxide or oxide, but the trials behind that grade used magnesium-rich mineral water and magnesium oxide, not citrate. We found no placebo-controlled trial of magnesium citrate for constipation, so we rate the citrate form 2.3,4 |
| Raising low magnesium levels | Limited | In a 7-week trial of 100 adults over 51 with poor sleep, 320 mg magnesium a day as citrate did not change serum magnesium across the whole group, but in the 37 people whose serum magnesium was low at the start, it raised levels while placebo did not. A 1990 study in healthy volunteers found citrate dissolved far better than magnesium oxide and raised urine magnesium (a marker of absorption) more after a single dose.5,6 |
| Poor sleep / insomnia symptomsCompare remedies for sleep → | Limited | The only citrate trial we found (100 adults over 51, 320 mg magnesium a day for about 7 weeks) saw sleep-quality scores improve from 10.4 to 6.6 whether people took magnesium or placebo, and a later review rated it at high risk of bias. That review's pooled 17-minute faster sleep onset in older adults came from two magnesium oxide trials, not citrate, and the evidence was graded low to very low.5,7 |
How much
Ranges below are what studies used and what supplements commonly contain. They are not a recommendation for you. Start at the low end.
How people take it
Safety
Who should avoid
- Kidney disease — magnesium can build up; the label says ask a doctor first
- Magnesium- or sodium-restricted diet — the label says ask a doctor first
- Abdominal pain, nausea or vomiting — ask a doctor before using it as a laxative
- Needing a laxative for over a week, or rectal bleeding — see a doctor
- Pregnancy and breastfeeding — the label says ask a health professional
- Children under 12 — lower label doses; under 2, ask a doctor
Known interactions
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Questions people ask
How fast does magnesium citrate work for constipation?
The US label says the oral solution generally produces a bowel movement within half an hour to 6 hours. It is meant for occasional constipation: the label says not to use it for more than a week unless a doctor advises it.
Is magnesium citrate better absorbed than other forms?
Better than magnesium oxide, on limited evidence: one 1990 study found citrate dissolved far better and raised urine magnesium more after a single dose. We found no independent study comparing citrate with glycinate or other forms, so we make no claim beyond oxide.
How much magnesium citrate is too much?
For supplements, the EU upper limit is 250 mg of magnesium a day and the US limit is 350 mg, both set to avoid diarrhoea; food magnesium does not count. A laxative dose of the solution holds about 1.9 to 2.9 g of magnesium, which is why the label limits it to short-term use and says to ask a doctor first if you have kidney disease.
Does magnesium citrate help you sleep?
Probably not more than a placebo, on the evidence we found. In the one citrate trial, people's sleep scores improved by the same amount on magnesium and on placebo, and reviews of magnesium for sleep rate the evidence low to very low.
Sources (10)
- Randomised controlled trial Peikert A, Wilimzig C, Köhne-Volland R. Prophylaxis of migraine with oral magnesium: results from a prospective, multi-center, placebo-controlled and double-blind randomized study. Cephalalgia. 1996.
- Systematic review von Luckner A, Riederer F. Magnesium in Migraine Prophylaxis-Is There an Evidence-Based Rationale? A Systematic Review. Headache. 2018.
- Systematic review Rao SSC, Brenner DM. Efficacy and Safety of Over-the-Counter Therapies for Chronic Constipation: An Updated Systematic Review. Am J Gastroenterol. 2021.
- Regulator label DailyMed. Magnesium Citrate (magnesium citrate) oral solution, Geri-Care Pharmaceuticals Corp: OTC drug label. Updated June 2026.
- Randomised controlled trial Nielsen FH, Johnson LK, Zeng H. Magnesium supplementation improves indicators of low magnesium status and inflammatory stress in adults older than 51 years with poor quality sleep. Magnes Res. 2010.
- Bioavailability study Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr. 1990.
- Systematic review and meta-analysis Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis. BMC Complementary Medicine and Therapies. 2021.
- Regulator opinion Scientific Committee on Food, European Commission. Opinion of the Scientific Committee on Food on the Tolerable Upper Intake Level of Magnesium. 2001.
- Review Costello R, Rosanoff A, Nielsen F, West C. Perspective: Call for Re-evaluation of the Tolerable Upper Intake Level for Magnesium Supplementation in Adults. Advances in Nutrition. 2023.
- Randomised crossover trial Attinger MC, von Felten S, Rodrigues CL, Krützfeldt J, Risch L, Bonzon J. Single Center, Open-Label, Randomized Crossover Trial on Drug-Drug Interactions of Levothyroxine/Magnesium-Citrate and Levothyroxine/Magnesium-Aspartate in Healthy Subjects-The ThyroMag Trial. Clin Transl Sci. 2025.
Last reviewed 10 October 2026 · Next review April 2027 · How we rate evidence
Reader notes
Experiences and questions from readers, read by an editor before they appear. They are personal accounts, not evidence, and are not medical advice.