Quick answer

Once absorbed, magnesium from citrate does what any magnesium does; the form changes how much gets in. In small human studies citrate was absorbed better than oxide, of which about 4% was absorbed in one test. Glycinate has little direct comparison, malate has no human comparison we could find, and L-threonate's few trials were funded by its makers.^1,2,3,4,5,6

Key facts

A 2021 systematic review of 14 studies found organic forms, such as citrate, generally better absorbed than inorganic ones, such as oxide.⁷
A 2017 review judged the dose and the body's own magnesium status to matter more than the type of salt.⁸
By weight, magnesium oxide is about 60% magnesium, bisglycinate about 14% and L-threonate about 7.5%.^5,9,10
Carbonate, chloride, gluconate and oxide are the forms most often linked to loose stools.¹¹

What every form provides

These two graded claims rest on the mineral itself, so they apply to citrate, glycinate, oxide, malate and L-threonate alike, as long as enough is absorbed.

Helps you reach the recommended daily magnesium intake*¹¹

Moderate evidence

National survey data from 2013 to 2016 show that 48% of Americans take in less magnesium from food and drink than the estimated average requirement. One serving supplies 275 mg, 65% of the Daily Value. In an earlier national survey, adults who used magnesium supplements had average total intakes well above requirement levels.

Amount studied: Recommended intake: 400 to 420 mg a day for men, 310 to 320 mg for women, from all sources

Contributes to normal muscle and nerve function*^11,12,13

Moderate evidence

A long-established role of the mineral, described by NIH and included in the EU list of permitted nutrient-function statements. It does not mean extra magnesium improves performance in people who already get enough: a meta-analysis of 14 trials found no significant gains in muscle strength or power, with benefits appearing only in groups likely to be short of magnesium, such as older adults.

Amount studied: Recommended daily intake from food and supplements

Citrate

Magnesium citrate dissolves well even without stomach acid. In small human studies it raised magnesium in blood or urine more than magnesium oxide did, both after a single dose and after 60 days of daily use.^1,2,14

In the longest of those studies, 46 healthy adults took 300 mg of magnesium a day for 60 days. Citrate gave the highest blood levels, and oxide did no better than placebo.²

Magnesium citrate is also sold as a liquid saline laxative. One such product holds 290 mg of magnesium per fluid ounce, with an adult dose of 6.5 to 10 fluid ounces.¹⁵

That liquid is a laxative for occasional use, not a daily supplement, so its dose says nothing about how much citrate to take each day.^11,15

Glycinate and bisglycinate

In the one isotope study of the glycinate form, 12 people absorbed about as much as from oxide overall, more in the four who absorbed oxide worst, and tolerated it better.⁴

Magnesium bisglycinate is mostly glycine by weight: in the sleep trial, each 893 mg capsule supplied 125 mg of magnesium.¹⁰

In a 2024 study funded by the maker of a competing form, 40 adults on a low-magnesium diet took single doses after an overnight fast. Blood magnesium rose significantly at one point after oxide and after citrate, but not at any point in the 6 hours after bisglycinate.¹⁶

No study we found compares glycinate with citrate head to head. On comfort, two findings point the same way: glycinate was better tolerated than oxide in the 12-person study, and in the sleep trial side effects were no more common than with placebo.^4,10

May modestly improve self-rated sleep in adults who sleep poorly*^10,17

Early evidence

One randomized, placebo-controlled trial tested this form: 155 adults who slept poorly took magnesium bisglycinate (250 mg of magnesium a day) or placebo for four weeks. Scores on a sleep-problem questionnaire fell a little more with magnesium (3.9 points against 2.3), a small effect, and other measures did not differ. It is a single short trial that relied on self-report. Older trials used other forms at higher doses in older adults and were rated low quality.

Amount studied: 250 mg a day as bisglycinate, 30 to 60 minutes before bed, for four weeks

Oxide

Magnesium oxide is about 60% magnesium by weight: a 400 mg tablet supplies 241.3 mg. It dissolves poorly, and in one study only about 4% of its magnesium was absorbed, less than from chloride, lactate or aspartate.^1,3,9

Magnesium oxide is also sold over the counter as an antacid for acid indigestion and upset stomach. Its label says antacids may interact with certain prescription drugs and that it may have a laxative effect.⁹

Oxide's advantage is density: at about 60% magnesium by weight, a small tablet carries a lot. Its drawbacks are how little is absorbed and a greater tendency to loosen stools.^3,9,11

Malate

Magnesium malate is on the EU list of permitted magnesium sources for supplements. No human study comparing its absorption with other forms was found. In a rat study it gave the highest blood levels of five forms, while citrate and oxide gave the lowest, the reverse of the human results for citrate.^18,19

So malate is a permitted form that EFSA expects to be about as available as the others, with almost no human research of its own. The rat study is the only source we found that ranks it first.^18,19

L-threonate

Magnesium L-threonate was developed after a 2010 study in which it raised magnesium in the brains of rats. The compound is about 7.5% magnesium: the human trials used 1 to 2 g of it a day, supplying about 75 to 145 mg of magnesium.^5,6,20

As magnesium L-threonate, may modestly improve some measures of sleep and memory in adults who report poor sleep*^5,6

Early evidence

Two short placebo-controlled trials, both funded by companies that sell this form, tested it in adults who reported poor sleep. In 80 adults taking 1 g of the compound a day (about 75 mg of magnesium) for 21 days, the main sleep questionnaire improved about as much with placebo, while ring-measured deep and REM sleep scores and several daytime ratings came out better with the compound. In 100 adults taking 2 g a day (145 mg of magnesium) for six weeks, overall scores on a computer test of thinking and memory, and on one sleep questionnaire, came out better, while ring-measured sleep and most other sleep measures did not differ. No trial by researchers independent of the makers was found.

Amount studied: 1 to 2 g a day of magnesium L-threonate (about 75 to 145 mg of magnesium), for three to six weeks

Compared with bisglycinate, L-threonate carries about half as much magnesium per gram, and its trials measured different things: ring scores, memory tests and questionnaires over three to six weeks, against one four-week questionnaire trial for bisglycinate. Neither has been tested against the other.^5,6,10

Choosing between them

A 2021 systematic review of 14 studies found organic forms generally better absorbed than inorganic ones, and the share absorbed depended on the dose. It concluded that any form can keep blood levels normal in healthy people who are not short of magnesium.⁷

A 2017 review concluded that the amount taken and a person's magnesium status matter more for absorption than the type of salt, and that more magnesium absorbed is usually followed by more passed in urine.⁸

For the most human absorption data: citrate.^1,2
For the most magnesium per gram of compound: oxide, at about 60% against 14% for bisglycinate, though little of it is absorbed.^3,9,10
For the form used in a placebo-controlled sleep trial: bisglycinate, with early evidence.¹⁰
Whatever the form, the label's magnesium line is what counts toward the 350 mg daily limit for supplements.²¹

What's in ours

What’s in ours

Magnesium Glycinate: Magnesium, 275 mg per serving, from the label
Men's Multi: Magnesium, 50 mg per serving, from the label
Creatine + Electrolytes: Magnesium, 60 mg per serving, from the label

Each of these labels names the form beside the amount: glycinate in Magnesium Glycinate, oxide in Men's Multi and malate in Creatine + Electrolytes.

Side effects by form

The forms most often reported to cause diarrhea are magnesium carbonate, chloride, gluconate and oxide.¹¹

Any form can cause diarrhea at high doses, and none changes the medicines magnesium interacts with. Ask a doctor first if you have kidney disease, or if you take antibiotics, bisphosphonates, diuretics, acid reducers, gabapentin or levothyroxine.^11,21

Questions people ask

Is magnesium citrate or glycinate better?

For absorption, citrate has more human data: it beat oxide in several small studies. Glycinate has one small isotope study against oxide and one sleep trial. No study compares the two directly, so neither can be called better on the evidence.^1,2,4,10

Is magnesium oxide worth taking?

It packs about 60% magnesium by weight, but only about 4% was absorbed in one study, and in a 60-day trial it did no better than placebo on blood levels. It is also sold as an antacid.^2,3,9

What is magnesium L-threonate for?

It was developed to raise magnesium in the brain, first tested in rats. Two trials in adults with poor sleep, both paid for by its makers, found mixed results on sleep and memory measures, graded early.^5,6,20

See what we make

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See the Full Measure line Creatine + Electrolytes Magnesium Glycinate Men's Multi

Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.