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Mineral

Magnesium

An essential mineral sold in many salt forms — glycinate, citrate, oxide and more — with very different elemental amounts.

Last reviewed September 28, 20265 sources6 forms
In short

Magnesium is an essential mineral involved in hundreds of enzyme reactions, including energy production, muscle and nerve function, and bone structure. Supplements come in many different “forms” — magnesium bound to another compound — and those forms differ in how much actual (elemental) magnesium they contain, how well they dissolve, and how often they cause digestive side effects.

When a label says “Magnesium 200 mg (as magnesium glycinate)”, the 200 mg should refer to elemental magnesium — the magnesium itself — not the total weight of the magnesium compound. Different forms carry very different percentages of elemental magnesium by weight, which is one reason capsules of the same size can deliver very different amounts.

Quick facts

Type
Essential mineral
Adult RDA (all sources)
310–420 mg/day depending on age and sex[1]
Upper limit from supplements
350 mg/day for adults (supplemental magnesium only; does not include food)[1]
How labels list it
Milligrams of elemental magnesium, followed by the form in parentheses[2]
Most common forms
Glycinate, citrate, oxide, malate, chloride, L-threonate

Common magnesium supplement forms

FORM · ~14% elemental

Magnesium Glycinate

Magnesium bound to the amino acid glycine, usually sold as “magnesium bisglycinate chelate”. It’s often chosen by people who want a form less likely…

Glycinate vs Citrate →
Glycinate vs Oxide →
FORM · ~16% elemental

Magnesium Citrate

Magnesium combined with citric acid. It dissolves well in water, has been studied for absorption more than most forms, and at higher amounts works…

Citrate vs Oxide →
Glycinate vs Citrate →
FORM · ~60% elemental

Magnesium Oxide

A compact, inexpensive form with a high percentage of elemental magnesium by weight but low water solubility. It’s common in budget tablets,…

Citrate vs Oxide →
Glycinate vs Oxide →
FORM · ~15% elemental

Magnesium Malate

Magnesium bound to malic acid. It’s marketed for energy and muscle comfort, but published human research specific to this form is limited.

FORM · ~12% elemental

Magnesium Chloride

A water-soluble magnesium salt used in liquid supplements, tablets and bath “flakes” or topical “oils”.

FORM · ~8% elemental

Magnesium L-Threonate

A newer, premium-priced form marketed for brain health. It contains a low percentage of elemental magnesium, and human research is early.

SuppScout calculation Percentages are approximate, calculated from molecular formulas; hydration and blends change real products.

What researchers have studied it for

The strongest evidence for magnesium supplements is simply that they raise magnesium intake, and that certain forms act as osmotic laxatives. Evidence for other outcomes — blood pressure, migraine, sleep — ranges from small-but-consistent to limited. Direct head-to-head research comparing forms is sparse and mostly measures short-term absorption markers rather than health outcomes.

Meeting magnesium needs

Consistent evidence

Many adults in the U.S. consume less magnesium than recommended from food. Supplements reliably increase magnesium intake; whether that matters for an individual depends on their diet and health status.[1]

Occasional constipation (certain forms)

Consistent evidence

Some magnesium compounds, including magnesium citrate and magnesium hydroxide, are used in over-the-counter laxative products because they draw water into the intestines. This is also why these forms are more likely to loosen stools at higher amounts.[1]

Blood pressure

Moderate evidence

Meta-analyses of clinical trials summarized by the NIH report that magnesium supplementation may lower blood pressure, but only to a small extent. It is not a substitute for prescribed treatment.[1]

Migraine

Mixed evidence

Some studies have examined magnesium for reducing migraine frequency, with mixed results. People with migraine should discuss options with a clinician.[1]

Sleep

Limited evidence

A 2021 systematic review of trials in older adults found low-quality evidence, from a small number of small studies, for modest effects on time to fall asleep. Evidence for specific forms (such as glycinate) is thinner still.[3]

Evidence labels summarize the overall body of published research for each topic; they are not a recommendation and do not mean a supplement is appropriate for you. Published research

Typical amounts in supplements

Single-ingredient magnesium supplements commonly provide roughly 100–400 mg of elemental magnesium per serving. For adults, the Tolerable Upper Intake Level for supplemental magnesium is 350 mg/day; this limit does not include magnesium from food. Some products exceed it per serving, which is a reason to read labels carefully and involve a clinician when using higher amounts.

[1]
Common per-serving range
100–400 mg elemental
Adult supplemental UL
350 mg/day
Children
Lower ULs apply — see ODS

These describe what supplements commonly contain and published reference values — not a recommendation for you.

Food sources

  • Pumpkin and chia seeds
  • Almonds and cashews
  • Spinach and other leafy greens
  • Black beans and edamame
  • Peanuts and peanut butter
  • Whole grains and fortified cereals
  • Soy milk

Source[1]

Potential considerations

  • Digestive effects: magnesium from supplements can cause diarrhea, nausea and abdominal cramping. The NIH notes this is especially common with carbonate, chloride, gluconate and oxide forms.
  • Very large amounts (for example, from magnesium-containing laxatives or antacids) can cause magnesium toxicity. People with impaired kidney function are at higher risk because the kidneys remove excess magnesium.
  • Label amounts refer to elemental magnesium. Comparing “magnesium glycinate 1,000 mg” (compound weight) with “magnesium 200 mg” (elemental) is not a like-for-like comparison.

Interactions and warnings

  • Bisphosphonates (used for osteoporosis): magnesium can reduce their absorption; doses are usually separated by at least 2 hours.[1]
  • Tetracycline and quinolone antibiotics: magnesium can form complexes that reduce absorption; timing should be separated as directed by a pharmacist.[1]
  • Diuretics: loop and thiazide diuretics can increase magnesium loss, while potassium-sparing diuretics can reduce it.[1]
  • Proton pump inhibitors: long-term use (typically over a year) can lower magnesium levels.[1]

Not a complete list. Ask a pharmacist or clinician about your specific medications.

Who should speak to a healthcare professional first

  • Anyone with kidney disease or reduced kidney function
  • People taking the medications listed above
  • Anyone who is pregnant or breastfeeding
  • Anyone considering amounts above the 350 mg/day supplemental upper limit
  • Anyone managing a diagnosed condition such as high blood pressure or migraine

Products containing magnesium

All 7 magnesium products →

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Related comparisons

MAGNESIUM

Citrate vs Oxide

The best-studied pair of magnesium forms, side by side.

Compare →
MAGNESIUM

Glycinate vs Citrate

Forms, label differences and what to compare before choosing.

Compare →
MAGNESIUM

Glycinate vs Oxide

Elemental content, solubility and cost per 100 mg.

Compare →

Guides & research

MAGNESIUM

How to Compare Magnesium Supplements

A five-step checklist: elemental amount, form, blends, other ingredients and cost per 100 mg.
LABEL BASICS

How to Read a Supplement Label

Serving size, amount per serving, ingredient form, other ingredients and testing information — in the order that matters.
EVIDENCE REVIEW

What the Research Says About Magnesium Forms and Absorption

Which comparisons have actually been studied, what they measured, and what’s still unknown.

Frequently asked questions

Which magnesium form is best?

There isn’t a single best form for everyone. Forms differ in elemental magnesium per capsule, digestive tolerance, price and research depth. Citrate is well studied for absorption and is also more likely to loosen stools; oxide is compact and inexpensive but less soluble; glycinate is often chosen for tolerability, though head-to-head research on it is limited. See glycinate vs citrate for a side-by-side view.

Why does my magnesium label say 200 mg when the capsule is much heavier?

U.S. supplement labels list the amount of the nutrient itself — elemental magnesium — not the whole compound. The rest of the weight is the part magnesium is bound to (for example glycine or citrate) plus other ingredients.

Does the 350 mg upper limit include food?

No. The adult Tolerable Upper Intake Level of 350 mg/day applies to magnesium from supplements and medications, not magnesium naturally present in food.

What does “buffered” magnesium glycinate mean?

It usually means the product blends magnesium glycinate with another form — often magnesium oxide — to fit more elemental magnesium per capsule at lower cost. Check the parentheses on the Supplement Facts panel: if more than one form is listed, the product is a blend.

Sources & references

  1. Magnesium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.govGovernment
  2. 21 CFR 101.36 — Nutrition labeling of dietary supplements. Electronic Code of Federal Regulations. ecfr.govRegulatory
  3. Mah J, Pitre T (2021). Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis. BMC Complementary Medicine and Therapies 21:125. pubmed.ncbi.nlm.nih.govMeta-analysis
  4. Magnesium: Fact Sheet for Consumers. NIH Office of Dietary Supplements. ods.od.nih.govGovernment
  5. Walker AF, Marakis G, Christie S, Byng M (2003). Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research 16(3). pubmed.ncbi.nlm.nih.govRandomized trial
  6. Lindberg JS, Zobitz MM, Poindexter JR, Pak CY (1990). Magnesium bioavailability from magnesium citrate and magnesium oxide. Journal of the American College of Nutrition 9(1). pubmed.ncbi.nlm.nih.govStudy

SuppScout links to primary and authoritative sources wherever possible. See our editorial policy for how sources are selected and how corrections are handled.

This page is educational and is not medical advice. Talk to a healthcare professional before starting a supplement, especially if you have a medical condition, take medications, or are pregnant or breastfeeding. Medical disclaimer.