Magnesium: which form does what, and who needs more

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.

The useful question is almost never whether you need magnesium. It is which salt you are holding, how much mineral is in it, and whether the thing you bought it for is something magnesium has been shown to do.

One disclosure first. Health Royals does not sell a magnesium product. None of our three formulas contains it, which is the only condition under which a piece like this can be written straight.

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. Two boxes that look identical can differ several times over in what they deliver.

• The nuance that matters most: magnesium depletion is uncommon in the Nordic countries and usually follows a disease or a medicine rather than an ordinary diet. Serum magnesium, the test you will be offered, also mirrors body stores poorly, so a normal value proves nothing and is not on its own a reason to start supplementing.

• Health Royals sells no magnesium product, and none of our three formulas contains magnesium. The same habit of reading applies to our own labels: named raw materials at stated doses, printed on the back rather than in the largest type on the front.

What does the number on a magnesium package actually mean?

It means one of two very different things, and only 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 very 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 does all the work, 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 says what a product would like to be called. The back says what it is.

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, and no supplier can improve on it.

  • 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.

Hold that list against a real label and the arithmetic gets uncomfortable. 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 defensible ranking, and it is not the ranking by mineral content.

Solubility matters more than density. The US Office of Dietary Supplements summarises it this way: forms that dissolve well are absorbed more completely, and magnesium as aspartate, citrate, lactate and chloride is more bioavailable than oxide or sulfate, in its magnesium fact sheet.

The head to head comparison people cite most is small. 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. Twenty men, one dose, one day. That is enough to prefer citrate over oxide, and not enough for the elaborate rankings that circulate online.

Glycinate and malate are widely called gentler on the stomach. The mechanism is plausible, since poorly absorbed magnesium sitting in the bowel is what draws in water, but the human comparisons that would settle it are missing.

Who in Sweden actually gets too little magnesium?

Far fewer people than the category implies, and mostly for reasons that have little to do with everyday diet.

The Nordic Nutrition Recommendations 2023 set an adequate intake of 350 mg a day for adult men and 300 mg for adult women, and report average intakes across Nordic and Baltic populations of 260 to 440 mg a day, in the magnesium chapter. The same chapter states plainly that magnesium depletion is uncommon and usually secondary to a disease or to a medicine. Livsmedelsverket publishes the Swedish summary of those reference values, in its reference value overview.

Real risk clusters in identifiable groups. The Office of Dietary Supplements lists gastrointestinal disease with malabsorption, type 2 diabetes, alcohol dependence and older age, in the same fact sheet. If you recognise yourself there, the conversation belongs with a doctor rather than with a shelf.

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. They do not say that more will do more, and that is the distinction most magnesium advertising quietly erases. The same holds for the other essential minerals, as we set out for zinc.

Can a blood test show whether you have magnesium deficiency?

Not reliably, because serum magnesium is a poor mirror of what is stored in the rest of the body.

Serum magnesium is the test you will be offered and the one most often over interpreted. The Office of Dietary Supplements notes that serum levels correlate poorly with total body magnesium or with concentrations in specific tissues, and says so directly.

A 2017 review in Current Opinion in Clinical Nutrition and Metabolic Care concluded that the most practical assessment combines serum magnesium, 24 hour urinary excretion and dietary intake, and that people in the lower part of the normal range may still be depleted, Costello and Nielsen, 2017. The scoping review prepared for the Nordic recommendations noted that functional indicators of magnesium status have been lacking, published in Food and Nutrition Research.

So a normal value on a routine panel does not prove you are replete, and it is not on its own a reason to start supplementing.

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 there is not enough evidence to say anything.

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 at all, 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 wrote that they were unable to reach a conclusion about effectiveness, Marshall and colleagues, 2019. That is absence of evidence rather than evidence of absence, but it is a long way from the confidence with which magnesium is recommended here. Symptoms that persist belong with a doctor.

What does the evidence not show?

It does not show that magnesium supplements reliably improve sleep in people who are not short of magnesium.

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 produced contradictory findings and an uncertain association between supplementation and sleep disorders, Arab and colleagues, 2023.

Magnesium L-threonate is where the sleep and cognition marketing has moved. 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, but no difference in objective sleep measures, the published trial report. One trial, six weeks, one branded material, with objective and subjective results pointing different ways.

EFSA has assessed magnesium L-threonate as safe under the proposed conditions of use and as a source from which magnesium is bioavailable, in its 2024 novel food opinion. That is a statement about absorption and safety, not an endorsement of any claim about the brain.

None of this says magnesium does not matter. It says the distance between an essential nutrient with authorised claims and a supplement that will repair your sleep is wider than the packaging suggests. 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.

How do you read a magnesium label in thirty seconds?

Find the salt, find the elemental figure, check how many capsules it refers to, then compare the total with the upper level.

  • Find the salt in the ingredient list. Oxide, carbonate, citrate, bisglycinate, malate, lactate, threonate. If the label says only magnesium, that silence is information.
  • 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 and rarely advertised.
  • 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, while the American upper level of 350 mg rests on the same endpoint with a different margin, as the fact sheet explains.

Then the part nobody selling magnesium will tell you. If you eat a varied diet with plenty of plant foods and have none of the risk conditions above, a magnesium supplement is a reasonable thing to skip. If you take one anyway, citrate at a modest dose is defensible.

We have no magnesium to sell you, which is why this article can end where the evidence ends. What we do make is a formula for the adjacent question of energy and everyday recovery, built from named raw materials at named doses: Peak Performance contains no magnesium, and its label says so.

Further reading

Frequently asked questions

Which magnesium is best?
There is no single best form, but solubility matters more than mineral content. Citrate, lactate and chloride are absorbed more completely than oxide and sulfate, and the head to head comparison people cite most was twenty men taking one dose. Citrate at a modest dose is defensible, and the elaborate rankings circulating online are guesswork.

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. Average intakes across Nordic and Baltic populations run between 260 and 440 mg a day, so most people are already inside that range. 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 most 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 no. 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. For exercise associated cramp there are no randomised trials at all, and cramp that persists belongs with a doctor.

Is magnesium glycinate better for sleep?
No evidence shows that. A 2023 systematic review covering nine studies and 7582 participants found contradictory results among the randomised trials and an uncertain association between supplementation and sleep disorders. Glycinate is often described as gentler on the stomach, which is a plausible mechanism that human comparisons have never settled.

Do I need a magnesium supplement at all?
Probably not, if you eat a varied diet with plenty of plant foods and have none of the conditions that genuinely raise risk: gastrointestinal disease with malabsorption, type 2 diabetes, alcohol dependence and older age. Health Royals sells no magnesium product, so we gain nothing from the answer. If you recognise yourself among those groups, the conversation belongs with a doctor rather than with a shelf.

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