MineralForms overview

Magnesium

Also called Mg, magnesium supplement, magnesium forms

By Kymata Health editorial teamLast reviewed October 8, 2026 · What changed

Kymata Health may earn a commission from links on separate product pages. This page contains no product links. Educational reference, not medical advice.

Summary

Magnesium is an essential mineral involved in more than 300 enzyme systems. In meta-analyses of human trials, supplements lowered blood pressure by about 2 mm Hg (grade A) and shortened time to fall asleep in older adults (grade C), but did not reduce leg cramps in older adults. Forms differ mainly in elemental content and absorption.

Top graded outcomes:A evidence grade Blood pressureC evidence grade Time to fall asleep (older adults)C evidence grade Arterial stiffness

Key facts

What it is
Essential mineral; cofactor in more than 300 enzyme systems. An adult body holds about 25 g, 50–60% of it in bone.[1]
Forms covered
Glycinate, citrate, L-threonate, malate, taurate, oxide[5][6][10][12][19][20]
Top studied outcomes
Blood pressure ↓ ~2 mm Hg (A); sleep onset latency in older adults ↓ ~17 min (C); muscle cramps in older adults: no effect[2][3][4]
Elemental content
From 8.3% (L-threonate) to 60.3% (oxide) of compound weight[5][6]
Label basis
US Supplement Facts panels declare elemental magnesium, not the weight of the whole compound[1]
RDA / upper limit
Adults 310–420 mg/day (all sources); UL 350 mg/day from supplements[1]
Main interaction classes
Bisphosphonates, tetracycline and quinolone antibiotics, diuretics, long-term PPIs, high-dose zinc[1][7][8]
Evidence base
4 graded human outcomes on this page
Last reviewed
October 8, 2026

How it works

EstablishedMagnesium is a cofactor for enzymes that regulate protein synthesis, muscle and nerve function, blood glucose and blood pressure, and it is needed for energy production and for moving calcium and potassium across cell membranes. The kidneys control body levels, which is why blood tests reflect total stores poorly.[1]

What the human research says

Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.

At a glance: strongest evidence per outcome

Evidence at a glance: strongest human evidence per outcome
OutcomeGradeEffectStrongest evidenceRows
HeartGrade AImprovedMeta-analysis · n = 2,028 · 2016Form tested: Various oral forms2 rows
SleepGrade CImprovedMeta-analysis · n = 151 · 2021Form tested: Oral magnesium (forms varied by trial)1 row
Healthy agingNo effectNo effectMeta-analysis · n = 307 · 2020Form tested: Oral magnesium (forms varied by trial)1 row

Every graded row

Outcome
Grade
Form tested
Sort

Showing 4 of 4 outcomes. Human trials only.

OutcomeEffectGradeBest evidencePMID
Blood pressureImprovedGrade A

Meta-analysis · n = 2,028 · 2016

34 double-blind placebo-controlled trials in normotensive and hypertensive adults

Form: Various oral forms · Dose: Median 368 mg/day magnesium · Duration: Median 3 months

Systolic blood pressure fell by 2.00 mm Hg and diastolic by 1.78 mm Hg versus placebo, with a 0.05 mmol/L rise in serum magnesium. A small average effect.

27402922 (opens PubMed)Source [2]
Arterial stiffnessMixedGrade C

RCT · n = 164 · 2022

Adults with overweight or mild obesity, mean age 63

Form: Magnesium citrate, oxide or sulfate · Dose: 450 mg/day magnesium · Duration: 24 weeks

No form changed pulse wave velocity or blood pressure versus placebo. An earlier 24-week trial (n=52, 350 mg/day) found a 1.0 m/s improvement, so results are mixed.

35253448 (opens PubMed)Source [9]
Time to fall asleep (older adults)ImprovedGrade C

Meta-analysis · n = 151 · 2021

3 RCTs in older adults with insomnia, in three countries

Form: Oral magnesium (forms varied by trial) · Dose: Varied by trial (not stated in the abstract) · Duration: Varied by trial

Sleep onset latency was 17.4 minutes shorter than placebo; total sleep time rose 16 minutes but not significantly. Trials were at moderate-to-high risk of bias; evidence quality low to very low.

33865376 (opens PubMed)Source [3]
Muscle cramps (older adults)No effectNo effect

Meta-analysis · n = 307 · 2020

Cochrane review; for idiopathic cramps, 5 trials in mostly older adults

Form: Oral magnesium (forms varied by trial) · Dose: Varied by trial · Duration: 4 weeks (primary endpoint)

No meaningful difference from placebo in cramps per week (−0.18/week, moderate-certainty evidence). Evidence for pregnancy-associated cramps was conflicting.

32956536 (opens PubMed)Source [4]

Forms compared

FormElemental %Absorption (human data)GI toleranceStudied for
Magnesium glycinate (bisglycinate)14.1%[10]Mg(C2H4NO2)2, MW 172.42; Mg 24.305 g/mol (anhydrous)In 12 people with ileal resection, overall absorption of a 100 mg dose did not differ from oxide (23.5% vs 22.8%), but was higher in the 4 with the poorest oxide absorption (23.5% vs 11.8%).[11]Better tolerated than oxide by all 12 patients in that small crossover trial.[11]Insomnia severity in adults reporting poor sleep (one RCT).
Magnesium citrate16.2%[12]Trimagnesium dicitrate Mg3(C6H5O7)2, MW 451.12 (anhydrous)More soluble and more bioavailable than oxide by urinary magnesium in short studies; in a 60-day RCT (n=46) citrate gave the highest serum magnesium of the forms compared.[13][14]Diarrhea was reported by 18.6% of participants at 600 mg/day in a 12-week migraine trial.[15]Arterial stiffness and blood pressure (null), bone-turnover markers, migraine attack frequency.
Magnesium L-threonate8.3%[5]Mg(C4H7O5)2, MW 294.50 (anhydrous); commercial ingredient may differNo head-to-head human absorption data. Raised brain magnesium in rats (animal data).[16]Described as well tolerated in 3- to 6-week trials of 1–2 g/day.[17][18]Cognitive test performance and sleep quality (small RCTs).
Magnesium malate15.5%[19]MgC4H4O5, MW 156.38 (anhydrous)No head-to-head human absorption data in our sources.No form-specific human tolerance data in our sources.No graded human outcome trials in our sources.
Magnesium taurate8.9%[20]Mg(C2H6NO3S)2, MW 272.6 (anhydrous)No head-to-head human absorption data in our sources.No form-specific human tolerance data in our sources.No graded human outcome trials in our sources.
Magnesium oxide60.3%[6]MgO, MW 40.305Lowest of the forms tested: about 4% fractional absorption in one comparison; poorly soluble in water.[21][13]One of the forms most often reported to cause diarrhea, per NIH ODS.[1]Arterial stiffness and blood pressure (null in one 24-week trial).
Elemental magnesium in 1,000 mg of each form

Arithmetic from the elemental percentages in the table above. More elemental content per gram says nothing about absorption or tolerance.

Compound weight → elemental magnesium

500 mg magnesium glycinate (bisglycinate) ≈ 71 mg elemental magnesium

Arithmetic only, from the elemental fractions in the table above. US Supplement Facts panels list the elemental amount; front-of-pack claims sometimes give the compound weight. Real products vary with hydration state and buffering.

Form pages: Magnesium citrate, Magnesium glycinate, Magnesium L-threonate

Studied doses

Doses studied in human trials ranged from about 243 to 973 mg/day of elemental magnesium, for 8 to 26 weeks, in the blood-pressure trials pooled by a Cochrane review that NIH ODS cites. Many of these exceed the 350 mg/day upper limit for supplements.[1]

Intake reference: Adult RDA 310–420 mg/day from all sources (by age and sex). Upper limit for supplemental magnesium: 350 mg/day for adults.[1] The upper limit covers supplements and medicines only, not magnesium in food. NIH ODS fact sheet (updated January 6, 2026).

These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.

Interactions

Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.

Medicines

  • Oral bisphosphonatesNIH fact sheete.g. alendronate (Fosamax)Magnesium-rich supplements or medicines can reduce bisphosphonate absorption; NIH ODS notes separating them by at least 2 hours.[1]
  • Tetracycline and quinolone antibioticsNIH fact sheete.g. doxycycline, ciprofloxacin, levofloxacinMagnesium can form insoluble complexes with these antibiotics; NIH ODS notes taking the antibiotic at least 2 hours before or 4–6 hours after magnesium.[1]
  • Potassium-sparing diureticsNIH fact sheete.g. amiloride, spironolactoneReduce urinary magnesium excretion.[1]

Medicines that can lower levels

  • Loop and thiazide diureticsNIH fact sheete.g. furosemide, bumetanide, hydrochlorothiazideLong-term use can increase urinary magnesium loss and lead to depletion.[1]
  • Proton pump inhibitors (long-term)FDA safety communicatione.g. esomeprazole, lansoprazoleUse typically longer than a year can cause low blood magnesium; in about 25% of cases FDA reviewed, supplements did not correct it and the PPI was stopped.[7][1]

Other supplements

  • High-dose zincPK studye.g. 142 mg/day zinc (as zinc sulfate)Lowered magnesium absorption and magnesium balance in a metabolic-ward study of adult men.[8]

Who should be careful

Kidney problems
The risk of magnesium toxicity rises with impaired kidney function, because the kidneys remove excess magnesium.[1]
High intakes and digestive effects
High doses from supplements or medicines often cause diarrhea, nausea and abdominal cramping. The adult upper limit for supplemental magnesium is 350 mg/day; very large doses from laxatives or antacids (typically over 5,000 mg/day) have caused toxicity.[1]
Pregnancy and breastfeeding
The RDA is 350–400 mg/day in pregnancy and 310–360 mg/day during lactation (all sources), and the 350 mg/day upper limit for supplemental magnesium still applies.[1]
Children
Upper limits for supplemental magnesium are lower: 65 mg/day at ages 1–3 and 110 mg/day at ages 4–8.[1]

Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.

Articles about Magnesium

Plain-English answers to common questions, built on the evidence above.

Frequently asked questions

Which form of magnesium is best absorbed?

Small human studies find citrate, aspartate, lactate and chloride better absorbed than oxide and sulfate. Glycinate matched oxide overall in one small crossover trial but did better in people with the poorest absorption. No head-to-head human data exist for threonate, malate or taurate.[1][11][14]

Why does my label say 100 mg when the capsule holds 700 mg of magnesium glycinate?

Supplement Facts panels list elemental magnesium. Magnesium glycinate is about 14% magnesium by weight, so 700 mg of the compound carries about 99 mg of magnesium. Front-of-pack claims sometimes give the compound weight instead.[1][10]

What is the upper limit for magnesium supplements?

For adults, 350 mg/day of magnesium from supplements and medicines. Magnesium in food does not count toward it, because the kidneys remove excess dietary magnesium.[1]

Does magnesium help with leg cramps?

A 2020 Cochrane review found it unlikely to provide meaningful relief for cramps in older adults. Evidence in pregnancy-associated cramps was conflicting.[4]

Can I get enough magnesium from food?

Leafy greens, legumes, nuts, seeds and whole grains are good sources, and about 30–40% of dietary magnesium is absorbed. Survey data show many people in the US eat less than the recommended amount.[1]

Sources

  1. [1]Magnesium: Fact Sheet for Health Professionals (updated January 6, 2026). NIH Office of Dietary Supplements, 2026. fact-sheet
  2. [2]Effects of Magnesium Supplementation on Blood Pressure: A Meta-Analysis of Randomized Double-Blind Placebo-Controlled Trials.. Hypertension, 2016. meta-analysis PMID 27402922
  3. [3]Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis.. BMC Complement Med Ther, 2021. meta-analysis PMID 33865376
  4. [4]Magnesium for skeletal muscle cramps.. Cochrane Database Syst Rev, 2020. meta-analysis PMID 32956536
  5. [5]Magnesium L-threonate (CID 45489777): C8H14MgO10, MW 294.50. PubChem, NIH, 2026. database
  6. [6]Magnesium oxide (CID 14792): MgO, MW 40.305. PubChem, NIH, 2026. database
  7. [7]FDA Drug Safety Communication: Low magnesium levels can be associated with long-term use of proton pump inhibitor drugs (PPIs). U.S. Food and Drug Administration, 2011. safety-communication
  8. [8]Inhibitory effects of zinc on magnesium balance and magnesium absorption in man.. J Am Coll Nutr, 1994. PK-study PMID 7836627
  9. [9]Effects of Magnesium Citrate, Magnesium Oxide, and Magnesium Sulfate Supplementation on Arterial Stiffness: A Randomized, Double-Blind, Placebo-Controlled Intervention Trial.. J Am Heart Assoc, 2022. RCT PMID 35253448
  10. [10]Magnesium glycinate (CID 84645): C4H8MgN2O4, MW 172.42. PubChem, NIH, 2026. database
  11. [11]Bioavailability of magnesium diglycinate vs magnesium oxide in patients with ileal resection.. JPEN J Parenter Enteral Nutr, 1994. crossover-RCT PMID 7815675
  12. [12]Trimagnesium dicitrate (CID 6099959): C12H10Mg3O14, MW 451.12. PubChem, NIH, 2026. database
  13. [13]Magnesium bioavailability from magnesium citrate and magnesium oxide.. J Am Coll Nutr, 1990. PK-study PMID 2407766
  14. [14]Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study.. Magnes Res, 2003. RCT PMID 14596323
  15. [15]Prophylaxis of migraine with oral magnesium: results from a prospective, multi-center, placebo-controlled and double-blind randomized study.. Cephalalgia, 1996. RCT PMID 8792038
  16. [16]Enhancement of learning and memory by elevating brain magnesium.. Neuron, 2010. animal-study PMID 20152124
  17. [17]Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems: A randomized controlled trial.. Sleep Med X, 2024. RCT PMID 39252819
  18. [18]The effects of magnesium L-threonate (Magtein®) on cognitive performance and sleep quality in adults: a randomised, double-blind, placebo-controlled trial.. Front Nutr, 2025. RCT PMID 41601871
  19. [19]Magnesium malate (CID 164748): C4H4MgO5, MW 156.38. PubChem, NIH, 2026. database
  20. [20]Magnesium taurate (CID 13343447): C4H12MgN2O6S2, MW 272.6. PubChem, NIH, 2026. database
  21. [21]Bioavailability of US commercial magnesium preparations.. Magnes Res, 2001. PK-study PMID 11794633

What changed

  1. October 8, 2026 · all · new pageFirst published.Writer: Kymata Health editorial team · No credentialed reviewer yet

How we write, grade and correct these pages: editorial and evidence policy.

Supplement & Nutrient Encyclopedia. Educational information only; it is not medical advice and does not replace a clinician. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Statements about supplements have not been evaluated by the FDA.