How much magnesium per day? UK amounts, and how much is too much
How much magnesium you need each day in the UK, how much is too much, and how to find the real magnesium figure on a supplement label.
- Written by
- Amy D
- Reviewed by
- Nooroots team
- Last updated
- Reading time
- 7 min read
Overview
UK adults need 300 mg of magnesium a day (men) or 270 mg (women), and the amount doesn't change after 65. The NHS says 400 mg or less a day from supplements is unlikely to cause harm; more can cause diarrhoea. Check the magnesium figure on the label, not the weight of the compound.
Key points
- Daily amount: the UK says 300 mg for men and 270 mg for women, at every adult age.
- Too much: the NHS says 400 mg or less a day from supplements is unlikely to cause harm.
- 500 mg: too much as magnesium, but 500 mg of magnesium glycinate gives only about 70 mg.
- Labels: go by the magnesium figure and %NRV, not the weight of the compound.
- Side effects: too much usually means loose stools; with kidney disease, ask your GP first.
How much magnesium per day do you need?
Adults in the UK need 300 mg of magnesium a day if they're men and 270 mg if they're women [1]. These amounts stay the same after 65 [2].
They're the UK's reference amounts, set to cover the needs of almost everyone. The NHS says you should be able to get all the magnesium you need from a varied diet [1].
| Who | Magnesium a day |
|---|---|
| Men aged 19 and over | 300 mg [1][2] |
| Women aged 19 and over | 270 mg [1][2] |
| Pregnancy | No increase [9] |
| Breastfeeding | 320 mg [9] |
Taking more doesn't keep raising your levels. Across 48 trials, magnesium in the blood rose with the dose but levelled off at around 300 mg a day from supplements Moderate [7].
How much magnesium per day for a woman?
270 mg a day, at every age from 19 [1][2]. That's 30 mg less than men need.
Many women fall short of it from food. UK women aged 19 to 64 get an average of 224 mg a day [2].
How much magnesium is too much?
From supplements, more than 400 mg a day. The NHS says 400 mg or less a day of magnesium from supplements is unlikely to cause any harm, but more than that for a short time can cause diarrhoea [1].
The 400 mg covers all your supplements together, multivitamins included. Under a 2004 agreement with industry, UK supplements that give more than 400 mg a day should carry a label warning that they may cause mild stomach upset in sensitive people [3].
There isn't enough evidence yet on high doses taken for a long time [1].
Is 500 mg of magnesium too much?
It depends on whether the 500 mg is magnesium or a magnesium compound. As 500 mg of magnesium from supplements, it's above the NHS's 400 mg line [1]. As 500 mg of magnesium glycinate, it gives only about 70 mg of magnesium.
That's because magnesium is joined to another substance, which makes up most of the weight. UK labels must show the magnesium in a daily dose and its share of the 375 mg nutrient reference value, or NRV [4][5]. Go by that figure, not the weight of the compound.
| Form | Magnesium in 500 mg |
|---|---|
| Oxide | About 300 mg |
| Citrate | About 60 to 80 mg |
| Malate | About 60 to 80 mg |
| Glycinate | About 70 mg |
| Threonate | About 40 mg |
These are our own sums from each compound's chemical formula, and they vary with how an ingredient is made. Read more in our guides to magnesium glycinate, citrate, malate and threonate.
What happens if you take too much magnesium?
Usually loose stools or diarrhoea. UK magnesium medicine leaflets say diarrhoea depends on the dose, and advise cutting back, then building up again slowly if needed [6].
Too much magnesium in the blood is a different matter. It usually happens only when a high intake meets kidneys that can't clear the extra, because healthy kidneys can pass out a lot of magnesium [6]. Signs include flushing, thirst, feeling sick, drowsiness, confusion and muscle weakness [6].
Do people in the UK get enough magnesium?
Most get close, but many fall short. UK men aged 19 to 64 get an average of 273 mg a day from food, and women 224 mg [2].
One in five men and about one in seven women in that age group get less than the UK's lower reference amount: 190 mg for men and 150 mg for women [2]. That lower amount is enough only for people with the smallest needs.
Cereals and cereal products, such as bread, supply about a third of the magnesium adults eat [2]. The NHS names spinach, nuts and wholemeal bread as good sources [1].
How much magnesium for sleep?
A 2025 trial used 250 mg of magnesium a day. In it, 155 adults who slept poorly took magnesium bisglycinate or a placebo 30 to 60 minutes before bed for 4 weeks, and their sleep scores improved a little more on magnesium Early [8].
The 250 mg was the magnesium, not the weight of the bisglycinate. For the wider research, see magnesium for sleep: what the research shows.
Should you split your magnesium dose?
It can help with larger amounts. Your gut absorbs a smaller share of magnesium as the dose rises [6]. In one study, the share absorbed fell from 65% at the lowest amount to 11% at the highest [10].
That's why UK magnesium medicines are taken in smaller doses up to three times a day [6]. If magnesium upsets your stomach, splitting the dose is the first thing to try.
Where Nooroots fits
Nooroots Triple Magnesium gives you 301 mg of magnesium a day, 80% of the NRV, from glycinate, citrate and malate in three capsules. Take them together or spread them through the day, whichever suits you.
Triple Magnesium's magnesium contributes to a reduction of tiredness and fatigue and to normal psychological function.
Coming soon. Triple Magnesium isn't on sale yet.
Frequently asked questions
How many grams of magnesium do you need a day?
About 0.3 g. UK amounts are given in milligrams: men need 300 mg (0.3 g) and women 270 mg (0.27 g) a day [1].
How much magnesium per day for a man?
300 mg a day, from age 19 into old age [1][2]. UK men aged 19 to 64 get an average of 273 mg a day from food [2].
How much magnesium glycinate should I take?
Go by the magnesium on the label, not the glycinate. Glycinate is about 14% magnesium, so 1,000 mg gives about 140 mg, and it takes nearly 3,000 mg to pass the NHS's 400 mg line [1]. Our magnesium glycinate guide has more.
What is elemental magnesium?
It's the magnesium itself, without the compound it's joined to. UK labels give it per daily dose, and every amount in this guide is elemental magnesium [5].
Is it safe to take magnesium every day?
Yes, for most adults, at 400 mg a day or less from supplements [1]. If you have kidney disease, ask your GP first.
References
Every study here is listed so you can read it yourself. This guide is for general information and doesn't replace advice from your GP or pharmacist. We review it when new research is published.
- NHS. Vitamins and minerals: others (magnesium section). Accessed 17 October 2026. nhs.uk/conditions/vitamins-and-minerals/others
- Office for Health Improvement and Disparities (2025). National Diet and Nutrition Survey 2019 to 2023 (chapter 5 tables 5.26, 5.41 and 5.62). Published 11 June 2025. gov.uk/government/statistics
- Department of Health (2011). Food supplements: label advisory statements and suggested reformulations. assets.publishing.service.gov.uk
- Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annex XIII (nutrient reference values), as it applies in Great Britain. legislation.gov.uk/eur/2011/1169/annex/XIII
- The Food Supplements (England) Regulations 2003 (SI 2003/1387), regulation 6. legislation.gov.uk/uksi/2003/1387/regulation/6
- Neoceuticals Ltd. Neomag 4 mmol chewable tablets: Summary of Product Characteristics (sections 4.2, 4.5, 4.8, 4.9 and 5.2). Electronic medicines compendium, updated 28 September 2026. medicines.org.uk/emc/product/2678/smpc
- Zhang X et al. (2016). The circulating concentration and 24-h urine excretion of magnesium dose- and time-dependently respond to oral magnesium supplementation in a meta-analysis of randomized controlled trials. Journal of Nutrition 146(3): 595–602. PMID 26865651
- Schuster J et al. (2025). Magnesium bisglycinate supplementation in healthy adults reporting poor sleep: a randomized, placebo-controlled trial. Nature and Science of Sleep 17: 2027–2040. doi:10.2147/NSS.S524348
- Department of Health (1991). Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. HMSO. Figures as reproduced in British Nutrition Foundation (2021), Nutrition requirements. nutrition.org.uk
- Fine KD et al. (1991). Intestinal absorption of magnesium from food and supplements. Journal of Clinical Investigation 88(2): 396–402. PMID 1864954
