Magnesium Glycinate vs Citrate: Which to Take

For constipation, choose magnesium citrate: it is sold as an over-the-counter saline laxative that usually works within 30 minutes to 6 hours¹. For sleep, neither is proven, but glycinate has the better result: one trial in 155 adults found a small benefit², while a citrate trial in 100 older adults found none beyond placebo³.

Citrate also has more human absorption data⁴. Neither form is likely to prevent ordinary night-time leg cramps in older adults⁵. Both are forms of magnesium, so the label's elemental magnesium dose matters more than the salt for most uses.

The difference is what the magnesium is bound to. Glycinate pairs each magnesium atom with two molecules of the amino acid glycine⁶. Citrate pairs magnesium with citric acid⁷.

Glycinate is an amino-acid chelate, and part of it may be absorbed intact through the small intestine's dipeptide transporters⁸. Citrate dissolves well in water and in stomach acid⁹. NIH names citrate, with aspartate, lactate and chloride, among the forms that tend to be absorbed better than magnesium oxide; its fact sheet does not rate glycinate¹⁰.

Side by side, from the sources cited in this guide^{6, 7, 1, 2}:

• Magnesium by weight: about 14.1% for glycinate (molecular weight 172.42) and 16.2% for citrate (molecular weight 451.12).
• Amount for 250 mg of magnesium: about 1.8 g of glycinate or 1.5 g of citrate, so the same dose takes a little more glycinate.
• Also delivers: glycine (glycinate) or citrate, a natural acid (citrate).
• Best-tested use: sleep for glycinate, in one trial; occasional constipation for citrate, as a labelled laxative.
• Gut effect: citrate draws water into the bowel at laxative doses; glycinate is not sold or labelled as a laxative.

Citrate has the stronger human data, but no study shows the gap between citrate and glycinate matters for health. Most trials compared each form against magnesium oxide, not against each other.

• Citrate vs oxide, 1990: oxide was only 43% soluble even in strong acid, while citrate was 55% soluble in plain water, and urinary magnesium rose more after citrate⁹.
• Three forms for 60 days, 2003: in 46 healthy adults taking 300 mg a day, citrate and an amino-acid chelate were absorbed better than oxide, and citrate gave the highest blood levels⁴.
• Citrate vs oxide, 2019: in 14 men given a single 400 mg dose, only citrate raised 24-hour urinary magnesium significantly¹¹.
• Four forms in one day, 2024: in 40 adults, a single dose of citrate raised plasma magnesium at 4 hours, while bisglycinate gave no significant rise¹².
• Glycinate vs oxide, 1994: in 12 people with part of the small bowel removed, absorption averaged 23.5% vs 22.8%, but glycinate absorbed twice as well in the 4 worst absorbers and was better tolerated⁸.

Two caveats. A 10-day study in 61 young women found oxide raised ionized magnesium more than citrate did¹³. And in lab tests of 15 commercial products, dissolution and absorption varied widely; the best and worst of them also differed when given to 30 people¹⁴.

Single-day comparisons that included both forms were designed to test a third, patented form^{15, 12}. Read them as small, short tests, not verdicts.

Both forms have been tested for sleep, though never against each other. Glycinate's trial found a modest benefit; citrate's found none beyond placebo.

In a 2025 randomized trial, 155 adults aged 18 to 65 with poor sleep took magnesium bisglycinate (250 mg of magnesium) or placebo². By week 4, insomnia scores fell 3.9 points with magnesium and 2.3 with placebo (p = 0.049), a small effect (d = 0.2). People who ate less magnesium seemed to benefit more.

In a 2010 randomized trial, 100 adults aged 51 to 85 with poor sleep took 320 mg of magnesium a day as citrate, or a placebo, for 7 weeks³. Sleep quality scores improved by about the same amount in both groups, so the trial could not show a benefit from magnesium.

The wider evidence on magnesium for sleep quality is thin. A 2021 meta-analysis found 3 trials in 151 older adults, including that citrate trial¹⁶. Pooling the 2 trials that timed sleep onset, both using magnesium oxide (55 people), people fell asleep 17.36 minutes faster; total sleep time did not change significantly, and the evidence was rated low to very low quality. One of those trials, in 46 older adults taking 500 mg a day as oxide for 8 weeks, improved insomnia scores and sleep efficiency^{17, 16}. See magnesium for insomnia for the full trial list.

Does the glycine help?

Possibly, but the dose is small. Glycine studies gave 3 g before bed¹⁸, and in rats glycine lowers core body temperature, one proposed way it aids sleep¹⁹. A 250 mg magnesium dose as glycinate carries roughly 1.5 g of glycine, about half that amount⁶. Glycine has its own page if you want the full dose.

Citrate. Liquid magnesium citrate is sold as an over-the-counter saline laxative, with 1.745 g of magnesium citrate (290 mg of magnesium) in each fluid ounce¹. The adult dose is 6.5 to 10 fl oz in 24 hours, taken with a full glass of water, and it is meant for occasional use.

That dose supplies about 1,900 to 2,900 mg of magnesium, five to eight times the 350 mg daily upper limit for magnesium from supplements and medicines^{1, 10}. Treat it as an occasional remedy, as the label intends, and ask a doctor first if you have kidney disease.

For ongoing constipation, the trials used magnesium oxide, another osmotic form, rather than citrate:

• 2019 trial: 34 women with mild to moderate constipation took 0.5 g of oxide 3 times a day for 28 days; 70.6% improved vs 25.0% on placebo²⁰.
• 2021 trial: in 90 adults, 1.5 g of oxide a day helped 68.3%, as many as senna (69.2%), against 11.7% on placebo²¹.
• 2023 meta-analysis: across 2 oxide trials, 68% responded vs 19% on control, with about 3.72 more bowel movements a week²².

The 2019 and 2021 trials both gave 1.5 g of oxide a day, about 900 mg of magnesium, well above that upper limit^{23, 10}, so take oxide for constipation only on a doctor's advice. We found no trial of supplement-dose citrate or glycinate for chronic constipation. Glycinate's reputation as the gentle form rests mainly on one small trial where it was better tolerated than oxide⁸. More on magnesium for constipation.

Probably neither. A 2020 Cochrane review of 11 trials in 735 people concluded magnesium is unlikely to give older adults meaningful protection from cramps⁵.

For idiopathic night cramps, mostly in people in their 60s, magnesium changed cramp frequency by just 0.18 fewer cramps a week (95% CI 0.84 fewer to 0.49 more) across 5 trials of 307 people⁵. Trials in pregnancy were conflicting, and none tested exercise cramps. Side effects, mostly diarrhoea, affected 11% to 37% of people taking magnesium, against 10% to 14% in the control groups.

Switching forms is unlikely to change this: the review included magnesium in any form⁵. If cramps come with a low blood magnesium level, treating the deficiency is a different question; see magnesium for muscle cramps.

Both forms supply the same mineral, and the pooled trials did not single out glycinate or citrate. The evidence is preliminary for anxiety and points to a small effect on blood pressure.

• Anxiety: a systematic review of 18 studies found benefit in 4 of 8 studies of mildly anxious people, but rated the evidence poor quality²⁴. See magnesium for anxiety.
• Blood pressure, 2016: 34 placebo-controlled trials in 2,028 adults, at a median 368 mg a day for 3 months, lowered blood pressure by 2.00/1.78 mm Hg²⁵.
• Blood pressure, 2025: 38 trials in 2,709 people found 2.81/2.05 mm Hg lower readings, with larger drops in treated hypertension (7.68 mm Hg systolic) and low blood magnesium (5.97 mm Hg), and no significant change in people with normal blood pressure²⁶.

NIH describes the blood pressure effect as marginal¹⁰, and the 2025 review found that results varied widely between trials²⁶. Don't expect an immediate drop: the trials measured effects after 4 weeks or more²⁶. If you have high blood pressure, read magnesium for blood pressure and tell your prescriber before adding it, because diuretics also change magnesium levels¹⁰.

For most healthy adults, yes. The trials gave each form every day: citrate for 60 days in an absorption study⁴ and bisglycinate in the sleep trial, with results at 4 weeks². Taking them together is fine too, as long as the combined total stays within the upper limit below. If you have kidney disease, ask your doctor first¹⁰.

The upper limit for magnesium from supplements and medicines is 350 mg a day for adults and children aged 9 and over, and lower for younger children¹⁰. That covers both products combined, but not the magnesium in food. The sleep trial's 250 mg of magnesium as glycinate plus a citrate capsule can pass it quickly².

Diarrhoea, nausea and abdominal cramping are the usual signs of too much¹⁰. To keep the gut settled:

• Split the dose into two smaller servings, for example one with dinner and one at bedtime.
• Use citrate where you want the laxative effect and glycinate where you don't.
• Add up the elemental magnesium on both labels, not the weight of the compound.

Gut disease, type 2 diabetes, alcohol dependence and older age are the main risk groups. Loop and thiazide diuretics, and proton pump inhibitors (acid-reducing drugs) taken for more than about a year, can lower magnesium status¹⁰. Symptomatic deficiency is uncommon in healthy people.

Early signs are loss of appetite, nausea, vomiting, fatigue and weakness¹⁰. Later come numbness, muscle cramps, seizures and abnormal heart rhythms. A blood test can mislead: under 1% of the body's magnesium is in serum, and 50% to 60% is in bone.

The kidneys control the balance, excreting about 120 mg a day and holding on to more when stores run low¹⁰. If you suspect magnesium deficiency, see magnesium for deficiency before choosing a form.

These groups should check with a clinician or pharmacist first^{10, 1}:

• People with kidney disease: kidneys that work less well can't clear excess magnesium, which raises the risk of toxicity, with low blood pressure, muscle weakness, an irregular heartbeat and, rarely, death. The citrate laxative label says to ask a doctor before use.
• People taking tetracycline or quinolone antibiotics: magnesium binds antibiotics such as doxycycline and ciprofloxacin, so take them at least 2 hours before or 4 to 6 hours after magnesium.
• People taking bisphosphonates for osteoporosis: magnesium can cut the absorption of tablets such as alendronate, so keep the two at least 2 hours apart.
• People on diuretics or proton pump inhibitors: these change magnesium status, so a dose that suits others may not suit you.
• Children: their upper limits are far lower, 65 mg a day at ages 1 to 3 and 110 mg at ages 4 to 8, and the laxative label sets smaller doses by age.
• Pregnant or breastfeeding people: the citrate laxative label asks you to check with a health professional first.

NIH gives these medicines as examples, not a complete list, and the citrate laxative label asks for a gap of at least 2 hours from any other drug^{10, 1}. Before using the laxative, ask a doctor if you have abdominal pain, nausea or vomiting, a sudden change in bowel habits lasting over 2 weeks, or a magnesium-restricted diet. Stop it and see a doctor if you have rectal bleeding or no bowel movement after use. Don't use it for more than a week without advice¹.

Pick by your goal, then by the elemental dose on the label^{1, 2, 3, 8, 5, 10}:

• Occasional constipation: liquid citrate, as the label directs, and only now and then.
• Poor sleep: glycinate at the trial dose of 250 mg of magnesium; expect a small effect at most, and judge it after 4 weeks.
• Low dietary intake: either form; citrate gives a little more magnesium per gram and has more absorption data.
• A sensitive gut: glycinate may be gentler, though it has only been compared with oxide; split it into two doses.
• Night-time leg cramps: neither is likely to help; ask your doctor about other causes.
• Kidney disease: neither, unless your doctor prescribes it.

Supplements in this guide

• Magnesium
• Glycine

We searched PubMed and a biomedical research index for absorption studies of magnesium salts and for trials of magnesium in sleep, constipation, cramps, anxiety and blood pressure. We also read the NIH Office of Dietary Supplements fact sheet, an over-the-counter magnesium citrate label on DailyMed and PubChem's entries for glycinate, citrate and oxide. We read 21 study records and cited all of them, and prioritised meta-analyses and randomized trials in adults.

No trial has compared glycinate with citrate for any health outcome, and the head-to-head absorption studies are small and short. The elemental percentages, glycine amounts and magnesium totals for the laxative and oxide doses are our calculations from PubChem's molecular weights and the label. Researched October 13, 2026. Reviewed and corrected October 14, 2026: we added the citrate sleep trial, NIH's spacing for antibiotics and bisphosphonates, and more of the laxative label's warnings.

1. U.S. National Library of Medicine, DailyMed. Magnesium citrate oral solution (saline laxative), OTC drug facts label, set ID f3847b0f-802d-73d7-e053-2a95a90a5bbe. Effective December 23, 2024. https://dailymed.nlm.nih.gov/dailymed/services/v2/spls/f3847b0f-802d-73d7-e053-2a95a90a5bbe.xml
2. Schuster J, et al. Magnesium Bisglycinate Supplementation in Healthy Adults Reporting Poor Sleep: A Randomized, Placebo-Controlled Trial. Nat Sci Sleep. 2025;17:2027-2040. doi:10.2147/NSS.S524348 Our study summary.
3. Nielsen FH, et al. Magnesium supplementation improves indicators of low magnesium status and inflammatory stress in adults older than 51 years with poor quality sleep. Magnes Res. 2010;23(4):158-68. https://pubmed.ncbi.nlm.nih.gov/21199787/
4. Walker AF, et al. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res. 2003;16(3):183-91. https://pubmed.ncbi.nlm.nih.gov/14596323/ Our study summary.
5. Garrison SR, et al. Magnesium for skeletal muscle cramps. Cochrane Database Syst Rev. 2020;9(9):CD009402. doi:10.1002/14651858.CD009402.pub3 Our study summary.
6. National Center for Biotechnology Information. PubChem Compound Summary for CID 84645, magnesium bis(2-aminoacetate) (magnesium glycinate): molecular formula and weight. https://pubchem.ncbi.nlm.nih.gov/compound/84645
7. National Center for Biotechnology Information. PubChem Compound Summary for CID 6099959, trimagnesium dicitrate (magnesium citrate): molecular formula and weight. https://pubchem.ncbi.nlm.nih.gov/compound/6099959
8. Schuette SA, et al. Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection. JPEN J Parenter Enteral Nutr. 1994;18(5):430-5. doi:10.1177/0148607194018005430
9. Lindberg JS, et al. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr. 1990;9(1):48-55. doi:10.1080/07315724.1990.10720349
10. National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. Updated January 6, 2026. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/
11. Werner T, et al. Assessment of bioavailability of Mg from Mg citrate and Mg oxide by measuring urinary excretion in Mg-saturated subjects. Magnes Res. 2019;32(3):63-71. https://pubmed.ncbi.nlm.nih.gov/32162607/
12. Pajuelo D, et al. Comparative Clinical Study on Magnesium Absorption and Side Effects After Oral Intake of Microencapsulated Magnesium (MAGSHAPETM Microcapsules) Versus Other Magnesium Sources. Nutrients. 2024;16(24). doi:10.3390/nu16244367
13. Ivanovic ND, et al. Effects of short-term magnesium supplementation on ionized, total magnesium and other relevant electrolytes levels. Biometals. 2022;35(2):267-283. doi:10.1007/s10534-022-00363-y
14. Blancquaert L, et al. Predicting and Testing Bioavailability of Magnesium Supplements. Nutrients. 2019;11(7). doi:10.3390/nu11071663
15. Brilli E, et al. Magnesium bioavailability after administration of sucrosomial® magnesium: results of an ex-vivo study and a comparative, double-blinded, cross-over study in healthy subjects. Eur Rev Med Pharmacol Sci. 2018;22(6):1843-1851. doi:10.26355/eurrev_201803_14605
16. Mah J, et al. Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis. BMC Complement Med Ther. 2021;21(1):125. doi:10.1186/s12906-021-03297-z Our study summary.
17. Abbasi B, et al. The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. J Res Med Sci. 2012;17(12):1161-9. https://pubmed.ncbi.nlm.nih.gov/23853635/ Our study summary.
18. Bannai M, et al. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Front Neurol. 2012;3:61. doi:10.3389/fneur.2012.00061 Our study summary.
19. Bannai M, et al. New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep. J Pharmacol Sci. 2012;118(2):145-8. doi:10.1254/jphs.11r04fm Our study summary.
20. Mori S, et al. A Randomized Double-blind Placebo-controlled Trial on the Effect of Magnesium Oxide in Patients With Chronic Constipation. J Neurogastroenterol Motil. 2019;25(4):563-575. doi:10.5056/jnm18194 Our study summary.
21. Morishita D, et al. Senna Versus Magnesium Oxide for the Treatment of Chronic Constipation: A Randomized, Placebo-Controlled Trial. Am J Gastroenterol. 2021;116(1):152-161. doi:10.14309/ajg.0000000000000942 Our study summary.
22. van der Schoot A, et al. The effect of food, vitamin, or mineral supplements on chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials. Neurogastroenterol Motil. 2023;35(11):e14613. doi:10.1111/nmo.14613
23. National Center for Biotechnology Information. PubChem Compound Summary for CID 14792, magnesium oxide: molecular formula and weight. https://pubchem.ncbi.nlm.nih.gov/compound/14792
24. Boyle NB, et al. The Effects of Magnesium Supplementation on Subjective Anxiety and Stress-A Systematic Review. Nutrients. 2017;9(5). doi:10.3390/nu9050429 Our study summary.
25. Zhang X, et al. Effects of Magnesium Supplementation on Blood Pressure: A Meta-Analysis of Randomized Double-Blind Placebo-Controlled Trials. Hypertension. 2016;68(2):324-33. doi:10.1161/HYPERTENSIONAHA.116.07664 Our study summary.
26. Argeros Z, et al. Magnesium Supplementation and Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Hypertension. 2025;82(11):1844-1856. doi:10.1161/HYPERTENSIONAHA.125.25129