Magnesium Dosage: How Much Per Day?

Vitality Supplements · Ingredient Guide

Magnesium Dosage

How much magnesium per day? A clear UK guide to reference intakes and the 375mg EU NRV, the crucial difference between elemental and compound weight, supplemental upper-level guidance, timing, and a dosage table you can use. Magnesium is an essential mineral sold as a food supplement in the UK.

Last updated July 2026 · Written by Vitality Supplements Editorial Team · ~2,300 words · 9 min read
Food supplement information — not medical advice
UK manufactured ISO/IEC 17025 batch tested Certificate of Analysis on request Evidence-referenced
Quick answer
How much magnesium should I take per day?
For labelling, the EU Nutrient Reference Value (NRV) for magnesium is 375mg per day. UK reference intakes are a little lower — around 300mg for men and 270mg for women. Most of that should come from food; a supplement is there to top up the gap. The single most important thing to understand is elemental vs compound weight: a label saying “1000mg magnesium citrate” does not mean 1000mg of magnesium — only a fraction is elemental magnesium. Keep supplemental magnesium within sensible upper-level guidance, and take it with food if you have a sensitive stomach.
Key takeaways
  • The EU NRV for magnesium (used on labels) is 375mg per day.
  • UK reference intakes are roughly 300mg/day for men and 270mg/day for women.
  • Elemental magnesium is what counts — compound weight is always higher.
  • Forms differ in elemental %: oxide is high, citrate ~16%, glycinate ~14%.
  • Keep supplemental magnesium within upper-level guidance to avoid loose stools.
  • Timing is flexible; take with food to reduce any digestive upset.
The numbers

Reference intakes

There are two sets of figures worth knowing. The EU Nutrient Reference Value (NRV) — the number used to calculate the “% NRV” on supplement and food labels — is 375mg of magnesium per day. Separately, UK dietary reference values set a Reference Nutrient Intake (RNI) of about 300mg/day for adult men and 270mg/day for adult women. These are targets for the whole diet, not a supplement dose. For background on the mineral, see what is magnesium.

A supplement's job is to help close the gap between what you eat and these targets. Under EU/UK rules, the authorised magnesium claims apply when a serving provides at least 15% of the 375mg NRV (about 56mg). At that level you can accurately say magnesium contributes to normal muscle function, to a reduction of tiredness and fatigue, to normal functioning of the nervous system and to the maintenance of normal bones and teeth.

Magnesium reference intakes & supplemental guidance (adults)
Figure Amount per day What it means
EU NRV (labelling) 375 mg The reference value used for “% NRV” on labels
UK RNI — men ~300 mg Whole-diet target for adult men
UK RNI — women ~270 mg Whole-diet target for adult women
15% NRV (claims threshold) ~56 mg Minimum per serving for authorised magnesium claims
EFSA supplemental upper level 250 mg Tolerable upper level for magnesium from supplements (readily dissociable salts), on top of diet
UK EVM guidance level ~400 mg Supplemental guidance level to avoid an osmotic (laxative) effect
The important bit

Elemental vs compound weight

This is where most people go wrong. Magnesium is never sold on its own — it is bound to another molecule to form a salt (oxide, citrate, glycinate and so on). The number on the front is often the weight of the whole compound, but your body only receives the elemental magnesium portion. Different forms carry very different percentages of elemental magnesium, so two products both saying “1000mg” can deliver wildly different amounts of actual magnesium.

For example, magnesium oxide is roughly 60% elemental by weight, so 1000mg of oxide provides about 600mg of magnesium — but oxide is less well absorbed. Magnesium citrate is around 16% elemental, and glycinate around 14%, but these chelated forms are better absorbed and gentler. This is why you should always look for the elemental figure per serving, not the compound weight. Our forms guide breaks down each form.

“1000mg” on the front is compound weight — what matters is the elemental magnesium inside.
Oxide
~60% elemental. Magnesium-dense but less bioavailable — high on paper, lower in practice.
Citrate
~16% elemental. Well absorbed, with a mild osmotic effect at higher doses.
Glycinate
~14% elemental. Well absorbed and the gentlest common form on digestion.
Multi-form
Several salts combined. Blends like Ultimate 8 mix higher-percentage and well-absorbed forms together.
Staying sensible

Upper level & timing

Magnesium from food has no upper limit of concern, because the body regulates it well. Magnesium from supplements is different: taken in excess, readily dissociable salts can have an osmotic effect and loosen the stools. EFSA set a tolerable upper level of 250mg/day for supplemental magnesium (on top of dietary intake), while the UK Expert Group on Vitamins and Minerals set a guidance level of around 400mg/day for supplemental magnesium. In practice, most everyday supplements sit comfortably within these figures.

On timing, magnesium is flexible — there is no single “best” time and it does not need to be taken on an empty stomach. Taking it with food can reduce any digestive upset. If you take a higher amount, splitting it across the day (for example morning and evening) is gentler than one large dose. Some people prefer the evening simply because it fits their routine; that is personal preference, not a claim.

  • Read the elemental figure — base your dose on elemental magnesium per serving, not compound weight.
  • Top up, don't replace — aim to fill the gap between diet and the reference intake.
  • Stay within upper-level guidance — keep supplemental magnesium sensible to avoid loose stools.
  • With food — helps if you have a sensitive stomach.
  • Split higher doses — gentler on digestion than a single large amount.
  • Ask a professional — especially if pregnant, breastfeeding, on medication or managing a health condition.

Our Ultimate 8 Magnesium provides 1000mg of magnesium complex across eight forms in a two-capsule daily serving — comfortably supplying a meaningful amount of magnesium (well above the 15% NRV claims threshold) while staying within sensible supplemental guidance. Not sure which form suits you? Compare glycinate vs citrate, or read the buyer's guide.

Common questions

Magnesium dosage FAQ

The EU NRV used on labels is 375mg/day. UK reference intakes are about 300mg/day for men and 270mg/day for women, mostly from food. A supplement is intended to top up the difference rather than provide the whole amount.
Elemental magnesium is the actual magnesium your body receives; compound weight is the weight of the whole salt (magnesium plus what it is bound to). Because forms carry different percentages — oxide ~60%, citrate ~16%, glycinate ~14% — always compare the elemental figure per serving, not the headline milligrams.
From food, excess is handled by the body. From supplements, too much can cause loose stools. EFSA set a tolerable upper level of 250mg/day for supplemental magnesium (readily dissociable salts), and the UK EVM a guidance level of about 400mg/day. Stay within sensible limits and split higher amounts across the day.
There is no single best time — magnesium can be taken whenever suits you. Taking it with food can reduce digestive upset, and splitting a higher dose morning and evening is gentler. Any preference for evening is about routine, not an authorised effect.
Ultimate 8 provides 1000mg of magnesium complex across eight forms per two-capsule serving. That comfortably supplies a meaningful amount of magnesium — well above the 15% NRV threshold at which the authorised claims apply — while staying within sensible supplemental guidance. See the label for the exact elemental figure.
When you get a meaningful amount, the authorised EU/UK claims apply: magnesium contributes to normal muscle function, to a reduction of tiredness and fatigue, to normal functioning of the nervous system, to normal psychological function, to electrolyte balance, to normal energy-yielding metabolism, to normal protein synthesis, to the maintenance of normal bones and teeth and to normal cell division. It is a food supplement, not a medicine.

Get your magnesium right

Ultimate 8 Magnesium provides 1000mg of magnesium complex across eight forms in one daily serving — UK-made and independently batch tested, with a Certificate of Analysis available on request. From £17.99 for a one-month supply.

Shop Ultimate 8 Magnesium → Compare the forms
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About the author. This guide was written and reviewed by the Vitality Supplements Editorial Team, a UK supplement manufacturer. Every batch we produce is independently tested by an ISO/IEC 17025-accredited laboratory, with a Certificate of Analysis available on request.

This article is for general information about food supplements and is not medical advice. Magnesium is sold as a food supplement in the UK; the health claims used here are the authorised EU/UK claims that apply when a product supplies a meaningful amount of magnesium. Do not exceed recommended intakes. Always consult a qualified healthcare professional before starting any supplement, particularly if you are pregnant, breastfeeding, taking medication or managing a health condition. References available on our research references page.