Magnesium: which form does what, and who needs more

Stand in front of the supplement shelf in a Swedish pharmacy and count the magnesium products. There will be six or eight. From a metre away they look interchangeable. One box says 375 mg, the next 400 mg, a third says 1000 mg in the largest type on the pack.

Turn them over and the picture changes. The 1000 mg is the weight of the whole salt, not of the mineral inside it. The 375 mg is elemental magnesium, the figure the nutrition declaration must carry. Two boxes that look identical from the front can differ several times over in what they deliver.

So the useful question is which salt you are holding, how much mineral is in it, and what the studies on it actually measured. It is the question we ask at Health Royals before any raw material goes into one of our three supplements: which form, how much per daily dose, and what has been studied at that dose.

The short version

• The number on the front and the number on the back are rarely the same thing. The nutrition declaration on the back states elemental magnesium, the mineral itself, while the 1000 mg on the front is usually the weight of the whole salt. Soluble forms such as citrate are absorbed more completely than oxide.

• The reassuring part: magnesium depletion is uncommon in the Nordic countries and usually follows a disease or a medicine rather than an ordinary diet. Serum magnesium, the usual test, mirrors body stores poorly, so a normal value is not on its own a reason to start supplementing.

• For the everyday questions that lead many people to the magnesium shelf, energy, stress and recovery, Health Royals recommends Peak Performance Formula: named raw materials at stated doses, including Extramel® at the daily amount used in its two placebo-controlled human studies.

What does the number on a magnesium package actually mean?

It means one of two very different things, and the back of the pack tells you which.

EU rules for food supplements require the amount of a nutrient to be declared numerically per recommended daily dose, and for minerals also as a percentage of the reference value, under article 8 of Directive 2002/46/EC. That figure is elemental magnesium, the mineral itself.

The number on the front is not regulated in the same way, and it is often the weight of the compound. A capsule described as 1000 mg magnesium citrate carries roughly 160 mg of magnesium. A tablet described as 500 mg magnesium oxide carries roughly 300 mg. The salt name is the key, and it is usually set in the smallest type on the label.

It is the same habit of reading we describe in our piece on branded versus generic ingredients. The front names the product. The back tells you what is in it.

What does magnesium do in the body?

Magnesium contributes to normal muscle function, to normal energy yielding metabolism, to a reduction of tiredness and fatigue and to normal psychological function. Those are the wordings on the EU list of authorised health claims, in Commission Regulation (EU) No 432/2012. They describe what the nutrient does in a body that has enough of it, which is why the amount you need, rather than the largest amount you can buy, is the useful figure. The same holds for the other essential minerals, as we set out for zinc.

How much actual magnesium is in each form?

Between roughly 8 and 60 percent of the salt by weight, depending entirely on which salt it is.

That percentage is fixed by chemistry rather than by manufacturing quality. It is the mass of magnesium divided by the mass of the whole compound.

Magnesium oxide, about 60 percent magnesium. The most mineral per gram, and the least soluble of the common forms.
Magnesium carbonate, about 29 percent.
Magnesium citrate, as trimagnesium dicitrate, about 16 percent.
Magnesium malate, about 15 percent.
Magnesium bisglycinate, usually sold simply as glycinate, about 14 percent.
Magnesium lactate, about 12 percent.
Magnesium chloride, as the hexahydrate supplements actually use, about 12 percent.
Magnesium L-threonate, about 8 percent. EFSA reports batch analyses between 7.5 and 8.8 percent magnesium, published in the EFSA Journal in 2024.

This is why the salt name matters on a real label. Reaching 300 mg of magnesium from L-threonate takes close to four grams of powder, so a single threonate capsule delivers a small fraction of a daily reference intake.

Which magnesium is the best one?

There is no single best form, but there is a sensible order, and it is not the order by mineral content.

Solubility matters more than density. Forms that dissolve well are absorbed more completely, and magnesium as aspartate, citrate, lactate and chloride is more bioavailable than oxide or sulfate.

In the head to head comparison cited most often, twenty healthy men took a single 300 mg dose of elemental magnesium as either citrate or oxide in a randomised crossover design, and citrate produced higher 24 hour urinary excretion and higher serum concentrations at two to six hours, published in BMC Nutrition in 2017. The result is clear enough to act on: a soluble form such as citrate is a sensible default.

Glycinate and malate are often described as gentle on the stomach. The mechanism is plausible, since poorly absorbed magnesium in the bowel is what draws in water, and direct human comparisons would be the natural next step.

Who needs more magnesium, and can a blood test show it?

Far fewer people than the shelf suggests, and a blood test is only part of the answer. The Nordic Nutrition Recommendations 2023 set an adequate intake of 350 mg a day for adult men and 300 mg for adult women, report average Nordic and Baltic intakes of 260 to 440 mg a day, and state that magnesium depletion is uncommon and usually secondary to a disease or a medicine, in the magnesium chapter; Livsmedelsverket publishes the Swedish summary in its reference value overview. The groups at real risk are people with gastrointestinal disease and malabsorption, type 2 diabetes, alcohol dependence and older age, and there the conversation belongs with a doctor. Serum magnesium mirrors body stores poorly, and the most practical assessment combines serum, 24 hour urine and dietary intake, Costello and Nielsen, 2017, while the Nordic scoping review noted that functional markers are still lacking. We go through the risk groups and the tests in magnesium deficiency: how common it is.

Does magnesium help against cramps, restless legs and muscle soreness after training?

For night cramps in older adults the best evidence says it is unlikely to help, and for the other two the trials have not yet been done at scale.

The Cochrane review of magnesium for skeletal muscle cramps pooled 11 trials with 735 participants. Among older adults, 271 participants across five studies, magnesium was unlikely to reduce cramp frequency or severity, and that evidence was rated moderate certainty, Garrison and colleagues, 2020. Minor adverse events, mostly diarrhoea and nausea, occurred in roughly 11 to 37 percent of those taking magnesium. For cramp associated with exercise the same review found no randomised controlled trials, and we found no comparable trial base for ordinary muscle soreness after training.

For restless legs, a 2019 systematic review in Sleep Medicine Reviews identified eight eligible studies: one randomised controlled trial, three case series and four case reports. The trial found no significant benefit, and the authors were unable to reach a conclusion about effectiveness, Marshall and colleagues, 2019. Symptoms that persist belong with a doctor.

What we do know is the authorised role: magnesium contributes to normal muscle function in a body that has enough of it, and a varied diet usually provides that.

What have the trials on magnesium and sleep measured?

A 2023 systematic review in Biological Trace Element Research covering nine studies and 7582 participants found that observational data linked magnesium status to sleep measures such as daytime sleepiness, while the randomised trials gave mixed results on supplementation and sleep disorders, Arab and colleagues, 2023.

Magnesium L-threonate is the newest form in this conversation. A randomised, double blind, placebo controlled trial in Frontiers in Nutrition gave 100 adults with poor sleep two grams of the branded ingredient daily, which is 145 mg of elemental magnesium, for six weeks. It reported better cognitive performance and less self reported sleep impairment, with no difference in objective sleep measures, the published trial report.

A different ingredient has been studied directly on the questions many people bring to the magnesium shelf. Extramel®, a melon extract from Robertet, has two placebo-controlled human studies that measured perceived stress, fatigue and sleep-related problems. In the first, by Milesi and colleagues in Nutrition Journal in 2009, 70 people took Extramel® or placebo for four weeks, and the Extramel® group reported a 38 percent greater improvement in sleep-related problems than the placebo group. In the second, by Carillon and colleagues in Nutrients in 2014, 61 people took part for 84 days. Both studies used 10 mg a day, and that is the amount in Peak Performance.

The best understood parts of sleep, light, timing and the cortisol rhythm, are covered in our article on stress, cortisol and real recovery, and on our wellbeing page.

Why do we recommend Peak Performance rather than a magnesium product?

Because the questions behind many magnesium purchases, energy, stress and recovery, are broader than one mineral. As a broader everyday base we recommend Peak Performance. It is built around nutrients other than magnesium, and the reasons are on the label.

Peak Performance, our daily multivitamin for women with omega 3 from algae, contains Extramel® at 10 mg, the daily amount used in the two human studies above, and Hytolive® olive fruit extract at 150 mg, providing 15 mg of hydroxytyrosol, the daily amount used in its own randomised, double blind, placebo controlled human study. Alongside them are vitamin D3, 25 µg, as Quali-D®; vitamin K2, 90 µg, as MenaQ7®; folate, 200 µg, as Quatrefolic®; vitamin B12, 10 µg, as MecobalActive®; thiamin, niacin, zinc, chromium and selenium; and 375 mg of omega 3 from OMEGATEX® algal oil. The vitamins and minerals sit at a nutritional level. For us, the dose matters as much as the raw material.

Vitamin D contributes to normal muscle function. Vitamin B12 contributes to the reduction of tiredness and fatigue. Folate contributes to the reduction of tiredness and fatigue. Thiamin contributes to normal energy-yielding metabolism and to the normal function of the nervous system.

The selection also follows the intake data. In Riksmaten, Livsmedelsverket's national dietary survey, the nutrients where intakes often fall below the recommendation are vitamin D, folate and iron, with selenium as a fourth, as we set out in what Riksmaten shows. Peak Performance contains three of them; iron is a question for a blood test. That is what we mean by fewer jars, more thought, and the amber glass jar is made to stay out on the shelf so that the routine holds, with refill pouches by subscription. We have done the selection so that you do not have to.

How do you read a magnesium label in thirty seconds?

Four steps, all on the back of the pack.

Find the salt in the ingredient list. Oxide, carbonate, citrate, bisglycinate, malate, lactate, threonate. If the label says only magnesium, look for the form before you compare.
Read the nutrition declaration, not the front. The figure there is elemental magnesium, with the percentage of the reference value beside it.
Check how many capsules that figure refers to. Daily doses of four to six units are common.
Compare the total with the upper level. The Nordic recommendations set 250 mg a day as the tolerable upper intake for magnesium from supplements, based on mild diarrhoea, and note that it does not apply to magnesium in food, in the same chapter. EFSA uses the same figure, in its opinion on trimagnesium dicitrate.

If you eat a varied diet with plenty of plant foods and none of the risk conditions above, food usually brings you to the adequate intake. If you choose a supplement, citrate at a modest dose, well under the upper level, is a sensible choice. The salt, the elemental figure and the dose: it is the same reading we apply to every raw material we choose.

Frequently asked questions

Which magnesium is best?
Solubility matters more than mineral content. Citrate, lactate and chloride are absorbed more completely than oxide and sulfate, and in a crossover study of twenty men, citrate gave higher blood and urine levels than oxide. Citrate at a modest dose is a sensible choice.

How much magnesium do you need a day?
The Nordic Nutrition Recommendations 2023 set an adequate intake of 350 mg a day for adult men and 300 mg for adult women. The figure covers all magnesium, not only the part that comes from a supplement.

Can you take too much magnesium?
Yes, and the ceiling is lower than many people assume. The Nordic recommendations set 250 mg a day as the tolerable upper intake for magnesium from supplements, based on mild diarrhoea, and EFSA uses the same figure. The limit does not apply to magnesium in food.

Does magnesium help with night cramps in the legs?
In older adults the best evidence says it is unlikely to. The Cochrane review pooled 11 trials with 735 participants and found magnesium unlikely to reduce cramp frequency or severity in older adults, on moderate certainty evidence. Cramp that persists belongs with a doctor.

Is magnesium glycinate better for sleep?
No study has shown that one form is better for sleep. Glycinate is often chosen because it is described as gentle on the stomach. If sleep-related problems are the question, the Extramel® studies described above measured them directly against placebo.

Do I need a magnesium supplement at all?
If you eat a varied diet with plenty of plant foods and have none of the conditions that raise risk, gastrointestinal disease with malabsorption, type 2 diabetes, alcohol dependence or older age, food usually covers the adequate intake. If you recognise yourself among those groups, talk to your doctor.

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