How much magnesium do you need a day?

Published

In the UK, the reference nutrient intake (RNI) for adults is 270 mg of magnesium a day for women and 300 mg for men; the European Food Safety Authority (EFSA) puts it at 300 mg and 350 mg. EFSA also sets an upper level of 250 mg a day for magnesium from supplements, which doesn’t count food. One sachet of Full Moon has 207 mg: below that level, on purpose.

  1. How much magnesium do adults need?

    Adults need about 270 mg (women) to 300 mg (men) a day by the UK’s figures, or 300 mg and 350 mg by EFSA’s. The UK figures are reference nutrient intakes, set by the Department of Health in 1991. EFSA’s are adequate intakes, from its 2015 opinion. Food labels use a third figure, the 375 mg Nutrient Reference Value, for % NRV.

  2. What is the upper level for magnesium from supplements?

    EFSA, the European Food Safety Authority, sets a tolerable upper intake level of 250 mg a day for adults and children from 4 years. It covers magnesium in supplements, magnesium added to foods and drinks, and magnesium in water, all added together across the day. In the UK, a 2003 expert group gave 400 mg a day of supplemental magnesium as a guidance level; we use EFSA’s lower 250 mg.

    From supplements, per day

    400 mg UK guidance level for supplemental magnesium (FSA expert group, 2003)

    EFSA’s level covers magnesium in supplements, magnesium added to foods and drinks, and water. It doesn’t count the magnesium naturally in food.

  3. Does magnesium from food count towards it?

    No. EFSA’s level doesn’t include the magnesium naturally present in food, such as nuts, seeds, wholegrains, beans, leafy greens, cocoa and milk. So eating these foods doesn’t take you towards it.

    Already in an ordinary day’s food
    • Porridge40 g oats46 mg
    • Wholemeal bread2 medium slices48 mg
    • Almondsa handful, 30 g81 mg
    • Milksemi-skimmed, 250 ml28 mg
    • Brown rice150 g cooked72 mg
    • Chickpeas80 g, drained35 mg
    • Spinach80 g, boiled27 mg
    • Cocoaheaped tsp, 5 g26 mg

    On average, from food: about 224 mg a day for women and 273 mg for men in the UK, and about 256 mg and 330 mg in Ireland.

    Per portion, from the UK’s food composition tables (CoFID, 2021). Average intake: National Diet and Nutrition Survey 2019 to 2023 (UK, adults 19 to 64) and National Adult Nutrition Survey II (Ireland, adults 19+).

  4. Why doesn’t Full Moon have more magnesium?

    We set it below EFSA’s 250 mg a day upper level for magnesium from supplements. A sachet has 207 mg, 55% of the Nutrient Reference Value. The level covers all your supplemental magnesium together, so if you also take a multivitamin with magnesium, count both towards the 250 mg.

    Full Moon magnesium hot cacao →

  5. What about higher-dose products?

    Many magnesium supplements sold in the UK and Ireland give 300 to 600 mg a day at their label dose. EFSA based its 250 mg level on a laxative effect: in studies, mild, temporary diarrhoea appeared in some adults at around 360 mg a day from supplements. We use EFSA’s 250 mg rather than the UK’s 400 mg guidance level.

  6. How do I compare magnesium on labels?

    Look for the magnesium line in the nutrition table, in mg and % NRV. A bigger number on the front can be the weight of the whole compound rather than the magnesium in it.

    How to read a magnesium label →

Sources

  1. EFSA (2006), Tolerable Upper Intake Levels for Vitamins and Minerals. Magnesium chapter (Scientific Committee on Food, 2001): 250 mg a day, supplemental magnesium only
  2. EFSA (2015), Scientific Opinion on Dietary Reference Values for magnesium. Adequate intake 350 mg (men), 300 mg (women)
  3. Regulation (EU) No 1169/2011, Annex XIII. Nutrient Reference Value for magnesium, 375 mg
  4. FSAI (2020), The Safety of Vitamins and Minerals in Food Supplements. Ireland adopts EFSA’s 250 mg level
  5. Expert Group on Vitamins and Minerals (2003), Safe Upper Levels for Vitamins and Minerals. Guidance level 400 mg a day, supplemental magnesium
  6. NHS, Vitamins and minerals: others. UK reference nutrient intakes
  7. McCance and Widdowson’s Composition of Foods Integrated Dataset (CoFID, 2021). Magnesium per 100 g for every food listed
  8. National Diet and Nutrition Survey 2019 to 2023. Table 5.41, adults 19 to 64, food only
  9. IUNA National Adult Nutrition Survey II (2026). Table 4.23, adults 19+
  10. Labels of seven high-strength magnesium supplements sold in the UK and Ireland. Brand and retailer product pages, checked 22 Oct 2026
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