How much magnesium should you take a day?

The EU labelling reference value is 375 mg a day, and that is the figure the percentage on the tub is calculated from. Food already provides a good part of it, so the supplement covers the difference. Above the reference there is no demonstrated extra benefit, and the gut lets you know first.

Which magnesium is best: oxide, citrate or bisglycinate?

It depends on what you compare. Oxide is the cheapest and carries the most magnesium per gram, but it is absorbed worse and often disagrees with people. Citrate and bisglycinate are better tolerated and better absorbed, at the cost of more money per milligram of magnesium. What does not change is the rule: look at elemental magnesium per serving, not the milligrams of the salt.

Does magnesium stop cramps?

EU regulation allows saying it contributes to normal muscle function, which is not the same as treating a cramp. Athletes’ cramps have more to do with fatigue, heat and hydration, and if they are frequent or painful they deserve a medical consultation rather than a tub.

Why does magnesium have no score on this site?

Because there is no citable effective dose comparable to creatine’s: what exists is a labelling reference value, not a dose shown to have an effect in healthy people. So these products are listed by price per capsule and certification level, and the score is left blank rather than invented.

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Magnesium · Moderate evidence

What magnesium is for and which to buy

The short answer. Magnesium is a mineral with functions recognised by EU regulation in muscle, the nervous system and tiredness, with a reference value of 375 mg a day. What almost nobody checks when buying it is that the tub does not contain magnesium: it contains a magnesium salt, and the fraction that is actually magnesium varies a lot between oxide and bisglycinate. Two tubs with the same milligrams on the label can provide double or half.

There are studies in favour, but few, with small samples or measuring markers instead of outcomes. No figure on this page is attributed to a specific product: the effect belongs to the ingredient and every number carries its source next to it.

01 What it does and how much

Each row is a measured effect, with the figure the study gives and the source number. Where the evidence gives no figure, the column says so instead of making up a percentage.

Effects of magnesium with their source
Effect	How much	Detail
EU daily reference value	375 mg	It is the NRV every label uses to calculate its percentage. It is not a therapeutic dose: it is the legal reference they are compared against. [1]
Functions authorised in the EU	muscle, nervous system and tiredness	Regulation allows saying it contributes to normal muscle and nervous system function and to reducing tiredness. "Normal" is the key word: maintaining what already works, not improving it beyond that. [2]
Elemental magnesium by salt	6 to 60 %	Magnesium oxide is around 60 % magnesium but poorly absorbed; bisglycinate carries much less per gram and is better tolerated. What to compare is elemental magnesium per serving, which the label is required to declare. [1]
Sports performance without deficiency	no demonstrated effect	As with other micronutrients: it corrects deficiencies, it does not improve people who have none. [3]

02 How to take it

Dose. Whatever is missing to get close to the day’s 375 mg counting food, not the whole tub by default.
When. With a meal. If you are after the effect on rest, in the evening.
How long before you notice it. If it corrects a low intake, days or weeks.

Details that change the result

Always compare "elemental magnesium per serving", never the milligrams of the salt. A tub of "magnesium citrate 1000 mg" can provide 150 mg of magnesium.
Oxide is the cheapest and the worst absorbed; it is also the one that loosens the bowels most, hence its laxative reputation.
Bisglycinate and citrate are better tolerated. They cost more per milligram of magnesium, and that is the decision.
Nuts, legumes, wholegrains and leafy greens provide magnesium every day. The supplement fills a gap; it does not replace them.

03 When it makes sense and when it does not

Worth it if

Low dietary intake for stretches: few vegetables, few nuts, little legumes.
Very heavy sweating and sustained intense training, where losses rise.
Medical advice, which is different from buying it just in case.

Not worth it if

Expecting more strength or performance without a low intake.
For cramps as if it were a treatment: the cause is usually something else and worth looking into.
Stacking three tubs that already contain magnesium (multivitamin, ZMA and electrolytes) without adding up the total.

04 Sources

Every figure above comes from here. They are position stands from scientific societies, meta-analyses and peer-reviewed reviews: if a claim cannot hang from one of these lines, it is not on the page. References are cited in their original form.

Reglamento (UE) 1169/2011 sobre la informacion alimentaria facilitada al consumidor, Anexo XIII: valores de referencia de nutrientes. Magnesio, 375 mg. https://eur-lex.europa.eu/legal-content/ES/TXT/?uri=CELEX%3A32011R1169
Reglamento (UE) 432/2012 de la Comision: lista de declaraciones de propiedades saludables autorizadas. Magnesio y funcion muscular normal, funcion normal del sistema nervioso y disminucion del cansancio. https://eur-lex.europa.eu/legal-content/ES/TXT/?uri=CELEX%3A32012R0432
Kerksick CM et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 2018;15:38. Los micronutrientes mejoran el rendimiento solo cuando corrigen un deficit previo. doi:10.1186/s12970-018-0242-y

This is not medical advice. It is what some studies say about an ingredient, not a protocol for you. With an illness, medication or pregnancy involved, the decision belongs to a healthcare professional who knows you.

Questions about magnesium

Answered with the data on this page

How much magnesium should you take a day?: The EU labelling reference value is 375 mg a day, and that is the figure the percentage on the tub is calculated from. Food already provides a good part of it, so the supplement covers the difference. Above the reference there is no demonstrated extra benefit, and the gut lets you know first.
Which magnesium is best: oxide, citrate or bisglycinate?: It depends on what you compare. Oxide is the cheapest and carries the most magnesium per gram, but it is absorbed worse and often disagrees with people. Citrate and bisglycinate are better tolerated and better absorbed, at the cost of more money per milligram of magnesium. What does not change is the rule: look at elemental magnesium per serving, not the milligrams of the salt.
Does magnesium stop cramps?: EU regulation allows saying it contributes to normal muscle function, which is not the same as treating a cramp. Athletes’ cramps have more to do with fatigue, heat and hydration, and if they are frequent or painful they deserve a medical consultation rather than a tub.
Why does magnesium have no score on this site?: Because there is no citable effective dose comparable to creatine’s: what exists is a labelling reference value, not a dose shown to have an effect in healthy people. So these products are listed by price per capsule and certification level, and the score is left blank rather than invented.

And now, which to buy

Prices, kept apart from the evidence

This page explains what magnesium does and deliberately names no brand. The comparison is the other half: 154 products from 13 stores from €0.042 per capsule, sorted by price and by how verifiable their certification is.

See the magnesium comparison

Other guides

What each supplement does, with its sources