Types of magnesium: every form compared, and which suits which goal

The word after "magnesium" on a supplement label names the molecule the mineral is bound to, and that partner molecule decides more than the marketing does. It sets how many milligrams of magnesium sit in each capsule, how much of that magnesium reaches your blood, and whether the capsule sends you to the bathroom. What magnesium does in the body, and who tends to run low, is covered in the LifeFrom magnesium guide.

The parent guide

Moderate evidence for blood pressureMagnesiumWhat magnesium does, how long a top-up takes, what it interacts with, and the blood tests that read itIn our shop

Every common form of magnesium, side by side

Counting the magnesium salts sold as supplements, laxatives, antacids and bath products, there are about a dozen common types of magnesium, plus blends that mix several. This chart lists each form's magnesium content, absorption, gut effect and uses. Absorption ratings are relative and come from small studies ²³⁴. Percentages are worked out from each salt's molecular weight and shift a little with how much water the salt crystal holds.

Elemental magnesium is the number on the label that counts

Elemental magnesium is the magnesium itself, weighed without its partner molecule. A 500 mg capsule of magnesium glycinate holds about 70 mg of elemental magnesium, because glycinate is about 14% magnesium by weight; a 500 mg tablet of magnesium oxide holds about 300 mg. A clear label prints the elemental figure, written as "Magnesium (as magnesium citrate) 200 mg", which means 200 mg of magnesium delivered as citrate. A label that reads "magnesium glycinate 500 mg" is giving the weight of the whole compound, and the magnesium inside is a seventh of that.

1. 1Find the magnesium lineOn a US Supplement Facts panel, look for the row that starts with "Magnesium", not the ingredient list underneath.
2. 2Look for the word "as""Magnesium (as glycinate) 120 mg" gives elemental magnesium. A compound name with a weight and no "as" gives the whole salt.
3. 3Convert a compound weightMultiply by the form's magnesium share from the table: 500 mg of citrate times 16% is about 80 mg of magnesium.
4. 4Add up every sourceThe adult upper limit for magnesium from supplements and medicines is 350 mg a day of elemental magnesium, set because of diarrhea, and antacids and laxatives count toward it; magnesium from food does not ¹. There is no benefit in taking magnesium up to the limit.

For scale, adults need 310 to 420 mg of magnesium a day from food and supplements together, depending on sex and age ¹. Two label words cause most of the confusion. "Buffered" magnesium glycinate is glycinate mixed with magnesium oxide, which raises the magnesium per capsule and brings some of oxide's laxative effect with it. "Chelated" means the magnesium is bound to an amino acid, as glycinate is; the word alone promises little, and a 60-day trial found magnesium citrate raised blood magnesium more than an amino-acid chelate did ³.

Is one form of magnesium absorbed better than another?

Yes, within limits. Forms that dissolve well tend to be absorbed better, and the NIH Office of Dietary Supplements summarises the small studies this way:

Forms of magnesium that dissolve well in liquid are more completely absorbed in the gut than less soluble forms.NIH Office of Dietary Supplements, Magnesium fact sheet for health professionals ¹

The clearest head-to-head data favour citrate over oxide. In Firoz and Graber's 2001 comparison of US products, magnesium oxide was the least absorbed, while chloride, lactate and aspartate did considerably better ². In a randomized, double-blind trial by Walker and colleagues in 2003, magnesium citrate raised blood and urine magnesium more than magnesium oxide or an amino-acid chelate over 60 days ³.

A 2021 systematic review by Pardo and colleagues found forms bound to a carbon-based partner, such as citrate, generally absorbed better than mineral forms such as oxide, and said the studies varied widely in design and quality ⁴. Most trials gave one dose to a few dozen healthy people and measured urine, so they say less about what happens over months of daily use. Magnesium glycinate has fewer head-to-head trials than its reputation suggests; its case rests mainly on gut comfort.

Magnesium glycinate: the gentle everyday pick

Magnesium glycinate, sold also as bisglycinate, is magnesium bound to two molecules of glycine, the smallest amino acid. Glycinate is widely reported to cause fewer loose stools than citrate or oxide, though few trials compare them directly, and that tolerance makes glycinate the usual choice for long-term topping up and for people who take magnesium in the evening. Glycine has small sleep trials of its own at gram-sized amounts, far more glycine than a magnesium capsule carries; the glycine page covers that evidence. Like every oral form, glycinate tops up body stores slowly, over weeks.

Magnesium citrate: well absorbed, and loosens stool

Magnesium citrate is the best-studied organic form for absorption, ahead of magnesium oxide in head-to-head trials such as Walker 2003 ³. Magnesium citrate also draws water into the bowel, so loose stools become more likely as the amount rises. That suits someone who is low on magnesium and also constipated. The large bottles of liquid magnesium citrate sold for bowel preparation contain far more magnesium than a supplement and belong to a different use.

Magnesium malate vs glycinate

Magnesium malate is magnesium bound to malic acid, a molecule cells use in energy production, and is about 15% magnesium by weight. Claims that malate helps fatigue or fibromyalgia rest on a few small trials that combined magnesium with malic acid, with mixed results, and none compared malate with glycinate. The common advice to take malate in the morning and glycinate at night is custom, with no trial behind it. For correcting a shortfall, malate and glycinate carry similar amounts of magnesium and are both gentle on the gut, so price and how your stomach responds are fair ways to choose.

Magnesium L-threonate: the brain form

Magnesium L-threonate was developed to raise magnesium inside the brain. In rats, L-threonate raised magnesium in the fluid around the brain and improved learning and memory, which other forms did not do as well ⁶. Human evidence is limited to a few small trials of a branded product; the main one, by Liu and colleagues in 2016, ran for 12 weeks against placebo in 44 older adults with memory complaints and reported gains on a composite thinking score ⁸. L-threonate is only about 7 to 8% magnesium by weight and costs several times more than glycinate, so it is a poor tool for correcting low magnesium. Between threonate and glycinate, the choice comes down to the aim: threonate for a brain-specific hope on thin evidence, glycinate for topping up.

Taurate, chloride, lactate and the other forms

Magnesium taurate pairs magnesium with taurine, an amino acid studied for heart rhythm and blood pressure; most of the research on the taurate salt itself is in animals. Magnesium chloride is well absorbed ², and a saturated solution of magnesium chloride is what sprays sell as "magnesium oil". Magnesium lactate and magnesium gluconate are gentle forms used in slow-release tablets and in some hospital oral replacement, though gluconate carries little magnesium per tablet. Magnesium orotate and aspartate are marketed for heart and energy claims, with little evidence to justify their price.

The partner molecules, on their own pages

Limited evidenceGlycineThe amino acid in magnesium glycinate, with small sleep trials of its own at gram-sized amountsIn our shop

Mixed evidenceTaurineThe amino acid in magnesium taurate; studied for blood pressure and heart healthIn our shop

Oxide, hydroxide and sulfate: the laxative forms

Magnesium oxide, hydroxide and sulfate carry a lot of magnesium per gram and are poorly absorbed, so most of the magnesium stays in the bowel and pulls water in. That water-pulling effect makes these three forms laxatives first and supplements second. Magnesium hydroxide is milk of magnesia, and Epsom salt is magnesium sulfate, sold for baths and as an oral laxative. Oxide is a common over-the-counter laxative, and it turns up in cheap multivitamins because it fits a large number of milligrams into a small tablet. The constipation page covers when a laxative is reasonable and when constipation needs a doctor.

Magnesium sprays, oils and Epsom baths: does magnesium absorb through skin?

No good evidence shows magnesium crossing intact skin in amounts that raise body levels. A 2017 review by Gröber and colleagues found the studies behind sprays, oils and creams small, poorly controlled or negative ⁵. "Magnesium oil" is a concentrated magnesium chloride solution with no oil in it, and the sting some people feel is skin irritation, with no link to being low on magnesium. Epsom salt baths have the same problem. A spray or bath is fine as a ritual; for correcting low magnesium, oral forms are the ones with data.

Which type of magnesium for which goal

• Low magnesium confirmed on a test: a clinician should look for the cause (diuretics, acid-reducing drugs, diarrhea, alcohol, diabetes) and choose the treatment; very low levels are treated medically, not with an over-the-counter form. Glycinate and citrate are the usual oral forms; see magnesium deficiency.
• Sleep: glycinate is the common pick for gut comfort; the sleep trials were small and used several forms, oxide among them. If sleep is the real problem, why can't I sleep covers the causes worth checking first.
• Anxiety or stress: glycinate is the usual pick for gut comfort; trials of magnesium for anxiety are small and mixed.
• Constipation: citrate, oxide or hydroxide, where the laxative effect is wanted; see constipation. See a doctor first if constipation is new and lasting, or comes with blood in or black stool, unexplained weight loss, severe belly pain or vomiting.
• Muscle cramps: a 2020 Cochrane review (Garrison and colleagues) judged magnesium unlikely to prevent ordinary cramps in older adults ⁷; see muscle cramps for the causes worth checking.
• Migraine prevention: magnesium is studied here, and the form and amount are ones to plan with a doctor.
• Sensitive stomach: glycinate, or malate.
• On a budget: citrate gives good absorption at a lower price than glycinate; oxide is cheapest and least absorbed.

How much, and when

Most magnesium supplements give somewhere between 100 and 350 mg of elemental magnesium a day, and the total from every supplement, antacid and laxative should stay under the 350 mg adult upper limit ¹. Starting at the low end and splitting the amount between two meals is the usual way to spare the gut, since loose stools are the first sign of too much. Taking magnesium with food is gentler on the stomach. Taking glycinate in the evening is habit rather than evidence; the form matters more than the hour. Oral forms raise body stores slowly, over weeks rather than days.

Who should check before taking any form of magnesium

CalculatoreGFR calculatorHave a creatinine result? Work out your eGFR, the number that says whether your kidneys can clear extra magnesium. For the rest of the kidney panel, see [how to read your renal panel](/learn/kidney-function-explained).Work it out

Know your magnesium level before you choose a form

Some people run low more often than others: older adults, people with type 2 diabetes, people who drink heavily, and people with gut conditions such as Crohn's or coeliac disease ¹; the magnesium deficiency page covers why. Serum magnesium is the standard blood test and catches true deficiency, but less than 1% of the body's magnesium is in the blood ¹, so a normal serum result does not rule out low stores. The magnesium guide explains why:

Red blood cell (RBC) magnesium, which measures magnesium inside red cells, is offered by some labs as an add-on, though it is not a standard diagnostic test. Calcium, potassium and vitamin D are often read beside magnesium, because low magnesium can drag the first two down; the electrolytes explainer shows how they fit together. If you start a supplement, a repeat test after a couple of months, agreed with your clinician, shows whether the form you chose is doing anything.

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