Types of Magnesium: Seven Forms Compared in One Table

Magnesium supplements differ mainly in what the mineral is bound to. That companion molecule changes three things you can feel or measure: how well the compound dissolves and is absorbed, how likely it is to loosen your stools, and how much actual magnesium fits into one capsule. It does not change the safety ceiling. For adults, the upper limit for magnesium from supplements and medicines is 350 mg a day of elemental magnesium (the mineral itself), whichever form you choose.

The evidence behind the different types of magnesium is uneven. Citrate, oxide and chloride have been compared in human absorption studies for many years. Glycinate has one recent sleep trial. Malate, taurate and L-threonate are often sold with specific promises, but most of what backs those promises comes from animal studies or a single small trial in people. The table below sets the seven common magnesium forms side by side, and the notes after it explain where each claim comes from.

Seven forms in one table

Here are the seven forms of magnesium compared on the points that matter when you read a label.

Form	Bound to	Absorption evidence in people	Bowel effect	What it is sold or studied for	Strength of evidence
Glycinate (bisglycinate)	Glycine, an amino acid	Organic form; few direct comparisons	Not used as a laxative	General top-up; a 2025 sleep trial	One good recent trial
Citrate	Citric acid	Better absorbed than oxide in small studies	Saline laxative at higher doses	General top-up; occasional constipation	Several small absorption studies
Oxide	Oxygen	Less completely absorbed than soluble forms	Among the forms most linked to diarrhea	Antacid and laxative products; many clinical trials	Well studied, poorer absorption
Malate	Malic acid	Little human data; one rat study ranked it high	Not well documented	Energy and muscle comfort claims	Mostly animal
L-threonate	L-threonic acid	Designed to raise brain magnesium in rats	Not well documented	Memory and cognition claims	Rat studies plus one small funded trial
Taurate	Taurine, an amino acid	Little human data; one rat study used a related acetyl taurate	Not well documented	Heart and calm claims	Mostly animal
Chloride	Chloride	Better absorbed than oxide in small studies	Among the forms most linked to diarrhea	Oral liquids and tablets; skin oils and flakes	Small absorption studies; skin route unsupported

How to read the table

Two rules from the NIH Office of Dietary Supplements (ODS) explain most of the absorption column. First, forms that dissolve well in liquid are absorbed more completely than forms that do not. Second, small human studies have found magnesium aspartate, citrate, lactate and chloride more bioavailable (more completely absorbed) than magnesium oxide and magnesium sulfate.

A 2021 systematic review of 14 comparison studies, published in Nutrition, reached a similar conclusion. Organic forms appear better absorbed than inorganic ones such as oxide. The review added that the share absorbed depends on the dose.

The same review also offered a reality check. In healthy people without a prior shortfall, any of the supplements studied could keep blood magnesium in the normal range. The differences between forms matter more for older adults, people with illnesses that affect absorption, and people starting from a low level.

Some products blend several forms under one name, often sold as a magnesium complex. The same rule applies to a blend: read the total elemental magnesium on the Supplement Facts panel. The name of the blend does not tell you which form supplies most of the mineral.

The bowel column also comes from ODS. High doses of magnesium salts cause diarrhea because magnesium that is not absorbed holds water in the gut. The forms most commonly reported to do this are carbonate, chloride, gluconate and oxide. Citrate is sold as a saline laxative in its own right.

Notes on each form

Glycinate

Glycinate is magnesium bound to the amino acid glycine. It is heavy for the magnesium it carries. In a 2025 placebo-controlled trial of magnesium bisglycinate published in Nature and Science of Sleep, an 893 mg capsule provided 125 mg of magnesium. That trial, in 155 adults with poor sleep, found a small improvement in insomnia scores at 250 mg of magnesium a day. Our glycinate vs citrate comparison covers it in detail.

Citrate

Citrate dissolves well and is one of the better-absorbed forms in small studies. The same property that helps absorption also lets it draw water into the bowel. That is why higher doses act as a laxative, and why some people choose it for occasional constipation.

Oxide

Oxide packs a lot of magnesium into a small weight. In a diabetes trial described by ODS, 500 mg of magnesium oxide supplied 300 mg of elemental magnesium. Compare that with 125 mg of magnesium from 893 mg of bisglycinate in the 2025 sleep trial. The trade-off is solubility: oxide dissolves poorly and is less completely absorbed. It is a common ingredient in antacids and laxatives.

Malate

Malate is magnesium bound to malic acid, a compound found in fruit. The main comparison we found is a 2019 study in rats, published in Biological Trace Element Research. It gave single doses of five compounds and found the highest overall blood exposure with malate. In that study, oxide and citrate came out lowest. That differs from the human studies above, and it is a reminder that rat results do not transfer neatly to people. Human evidence for malate is limited.

L-threonate

L-threonate was developed by researchers who showed, in a 2010 rat study published in Neuron, that it raised brain magnesium and improved learning and memory in the animals.

The main human trial, published in 2016 in the Journal of Alzheimer’s Disease, enrolled 51 adults aged 50 to 70. They reported memory and concentration complaints along with poor sleep and anxiety, and 44 of them were analyzed over 12 weeks. The trial reported improved scores on a composite cognitive measure (a score that combines several tests). Effects on sleep and anxiety could not be judged, because the placebo group improved strongly too. The trial was funded by the company that developed the compound. It is an interesting lead, not settled evidence.

Taurate

Taurate is magnesium paired with taurine, an amino acid. The 2019 rat study tested a related compound, magnesium acetyl taurate. It was absorbed quickly, gave the highest levels in brain tissue and was linked to fewer signs of anxiety in the animals. Human trials of magnesium taurate are scarce, so claims about heart health or calm are ahead of the evidence.

Chloride

Chloride is absorbed better than oxide in small studies. ODS describes at least one clinical trial that used it as an oral liquid, at 300 mg of elemental magnesium a day. It also turns up in sprays, oils and bath flakes. A 2017 review in Nutrients looked at those skin products and concluded that the case for meaningful magnesium absorption through the skin is scientifically unsupported.

Other forms you may see

• Aspartate and lactate: these turn up less often on labels, but both were among the better-absorbed forms in the small studies ODS summarizes.
• Sulfate: this is the form in Epsom salt. Taken by mouth, it is one of the less well absorbed forms. As a bath soak, the skin-absorption review applies.
• Hydroxide: the active form in milk of magnesia and many antacids. ODS gives the example of a milk of magnesia laxative that supplies 500 mg of elemental magnesium per tablespoon, well above the supplement limit, although some of it is not absorbed because of the laxative effect. These products count toward your daily total.

Choosing between them

• For a general top-up: citrate or glycinate, at a dose that keeps you within 350 mg a day from supplements.
• If your stomach is sensitive: start with glycinate or a small dose split across the day, and step back if your stools loosen.
• If you are paying more for malate, threonate or taurate: you are paying for a hypothesis, mostly tested in animals.
• If you need magnesium for a medical reason, such as a low level found on a blood test or a condition that affects absorption: the form and dose are your clinician’s call.
• Whatever product you choose: compare elemental magnesium on the Supplement Facts panel, and check how much you already get from food with the nutrient RDA lookup.

For how much to take and when, see our pages on magnesium dosage and the upper limit and when to take magnesium.

Who should be careful

• Kidney disease: do not take magnesium supplements without medical advice. ODS notes that the risk of toxicity rises when the kidneys cannot clear the excess.
• Tetracycline or quinolone antibiotics: leave a gap. ODS advises taking the antibiotic at least 2 hours before or 4 to 6 hours after magnesium.
• Oral bisphosphonates (bone-density medicines): keep magnesium at least 2 hours away from the dose.
• Long-term proton pump inhibitors or diuretics: ask your prescriber before adding magnesium, since these medicines can raise or lower magnesium levels.
• Combining products: if you take a magnesium supplement plus an antacid or laxative that contains magnesium, add up the elemental totals so you know your real daily amount.