How Much Magnesium Per Day in the UK? Dosage by Age & Sex (2026)
The NHS says adults need 300 mg of magnesium a day (men) or 270 mg (women), and most people can get it from food. From a supplement, 250 mg a day or less stays under the EU’s safe limit; the NHS says 400 mg or less is unlikely to cause harm.
A summary of NHS, EFSA and UK expert-group guidance, not medical advice. Ask your GP or pharmacist before taking magnesium if you have kidney disease or take prescription medicines.
Magnesium sold in the UK, matched to your dose
Each amount is the magnesium itself, from the label. Costs are each brand’s own UK list price, read October 15, 2026.
- Buy on Amazon for Solgar Magnesium Glycinate
Our pick: one serving under every limit
Solgar Magnesium Glycinate £0.53 a day for 240 mg
240 mg (64% NRV) in 2 capsules, all bisglycinate. Under EFSA’s 250 mg. Sold by Amazon UK.
- Check price for Lamberts Gentle Magnesium Bisglycinate
Set your own dose, 150 mg at a time
Lamberts Gentle Magnesium Bisglycinate £0.20 a capsule
150 mg a capsule (40% NRV). One is a light top-up; two (300 mg) is over EFSA’s 250 mg but under the NHS’s 400 mg.
- Check price for Lamberts MagAsorb Magnesium Citrate 150 mg
The lowest cost per mg
Lamberts MagAsorb Magnesium Citrate 150 mg £0.26 per 300 mg
150 mg of magnesium as citrate a tablet. Citrate can loosen stools at higher doses.
Other doses:
- Pure Encapsulations Magnesium Glycinate 120 mg: 120 mg a capsule, glycinate; 2-pack only on Amazon UK, no UK price we could read.
- Solgar Magnesium Citrate: 200 mg a tablet (citrate). The label’s 2 tablets give 400 mg (107% NRV), over EFSA’s limit; take 1.
- Doctor’s Best High Absorption Magnesium: 100 mg a tablet, 2 per serving; imported. The label allows 2 tablets twice a day (400 mg).
How Much Magnesium Per Day? The UK Numbers
| Who | UK | EFSA (EU) | US NIH |
|---|---|---|---|
| Children 1–3 years | 85 mg | — | — |
| Children 4–6 years | 120 mg | — | — |
| Children 7–10 years | 200 mg | — | — |
| Children 11–14 years | 280 mg | — | — |
| Children 15–18 years | 300 mg | — | — |
| Men, 19–64 | 300 mg | 350 mg | 400–420 mg |
| Women, 19–64 | 270 mg | 300 mg | 310–320 mg |
| Adults 65 and over | 300 mg (men), 270 mg (women) | 350 / 300 mg | 420 / 320 mg |
| Pregnancy | no extra | 300 mg | 350–400 mg |
| Breastfeeding | +50 mg (320 mg) | 300 mg | 310–360 mg |
Children’s figures are from the UK government’s dietary recommendations (the same for boys and girls). Children should not take an adult supplement unless a doctor says so. The UK figure is lower than the US one. The NHS says You should be able to get all the magnesium you need by eating a varied and balanced diet.
It names spinach, nuts and wholemeal bread as good sources. A supplement is a top-up, not a replacement for food.
How Much Is Too Much? Three Limits
| Item | Value (mg) |
|---|---|
| EFSA safe upper limit (EU) | 250 mg |
| US NIH upper limit | 350 mg |
| NHS: “unlikely to cause any harm” | 400 mg |
- EFSA, 250 mg. The safe upper limit for magnesium from supplements, water and fortified foods, from age 4. It was set because more can cause mild, short-lived diarrhoea. It does not count the magnesium that is naturally in food and drinks.
- NHS, 400 mg.
Having 400mg or less a day of magnesium from supplements is unlikely to cause any harm.
It also says more than 400 mg for a short time can cause diarrhoea. The figure comes from the UK expert group’s 2003 report, which gave itfor guidance purposes only
. - US, 350 mg. You will see this on US websites and many Amazon listings.
If you want one number, use 250 mg: a supplement at or under it is under all three. If you have kidney disease, ask your doctor before you take magnesium. Weak kidneys cannot clear the extra, so it can build up.
Reading a UK Label: % NRV
UK and EU labels give magnesium as a share of the nutrient reference value (NRV), which is 375 mg. Use this table to turn the % back into milligrams.
| Magnesium | % NRV | Against the limits |
|---|---|---|
| 100 mg | 27% | under all three limits |
| 120 mg | 32% | under all three limits |
| 150 mg | 40% | under all three limits |
| 200 mg | 53% | under all three limits |
| 240 mg | 64% | under all three limits |
| 250 mg | 67% | under all three limits |
| 300 mg | 80% | over EFSA’s 250 mg |
| 375 mg | 100% | over EFSA’s 250 mg and the US 350 mg |
| 400 mg | 107% | over EFSA’s 250 mg and the US 350 mg |
Check which number is the magnesium. The magnesium line on the label is the magnesium itself. The front of the tub may show the whole compound: 1,000 mg of magnesium bisglycinate holds only about 140 mg of magnesium. And look at the words in brackets: three of the UK “bisglycinate” listings we read also contained magnesium oxide.
Amounts Used in Published Trials
These are amounts researchers gave, not advice. Many are above the UK and EU lines for supplements, and were given under supervision.
| Goal | Amount studied | What was found |
|---|---|---|
| Sleep | 320–729 mg (3 trials, older adults); 250 mg as bisglycinate (2025) | Fell asleep about 17 minutes faster, low-quality evidence (Mah 2021); a small effect in the 2025 trial (Schuster 2025) |
| Night-time leg cramps | 226 mg as magnesium oxide (Barna 2021) | A small drop in cramp count against placebo; a Cochrane review found no clear benefit for older adults with general cramps |
| Constipation | Magnesium oxide | 68% improved on oxide vs 19% on placebo in 2 trials (van der Schoot 2023) |
For each trial, see magnesium and sleep and muscle cramps (US pages; the research is the same everywhere).
When to Take Magnesium, and What to Space It From
- Any time you will remember. Take it with food if it upsets your stomach, or split it between two meals.
- Antibiotics: take tetracyclines (such as doxycycline) or quinolones (such as ciprofloxacin) at least 2 hours before or 4 to 6 hours after magnesium (US NIH).
- Osteoporosis drugs (bisphosphonates such as alendronate): take them at least 2 hours apart from magnesium (US NIH).
- Heartburn pills (PPIs such as esomeprazole or lansoprazole), taken for a year or more, can lower magnesium. In about 1 in 4 of the cases FDA reviewed, supplements did not raise it and the PPI had to be stopped (US NIH).
Frequently Asked Questions
How much magnesium should I take per day in the UK?
The NHS says adults aged 19 to 64 need 300 mg a day (men) or 270 mg (women), and that you should be able to get it all from a varied diet. If you take a supplement, 250 mg a day or less keeps you under EFSA’s safe limit for supplements; the NHS says 400 mg or less is unlikely to cause harm.
Is 400 mg of magnesium a day too much?
From supplements, 400 mg is the most the NHS says is unlikely to cause harm, and it says more than 400 mg can cause diarrhoea. It is over EFSA’s 250 mg limit and the US 350 mg limit. From food, there is no limit.
Why do the UK, EU and US limits differ?
They read the same diarrhoea studies differently. EFSA set 250 mg as the dose with no effect in the trials. The US set 350 mg. The UK expert group said there was not enough data for a safe upper level and gave 400 mg as guidance only.
What does % NRV mean for magnesium?
NRV is the nutrient reference value on UK and EU labels: 375 mg for magnesium. 50% NRV is about 190 mg; 100% NRV is 375 mg, which is over EFSA’s 250 mg limit for supplements.
Is the dose on the front of the bottle the magnesium?
Not always. The magnesium line on the label is the magnesium itself. The front may show the whole compound: 1,000 mg of magnesium bisglycinate holds only about 140 mg of magnesium.
How much magnesium during pregnancy?
UK figures add nothing for pregnancy and 50 mg a day while breastfeeding (320 mg; Department of Health, 1991). EFSA sets the same 300 mg a day in pregnancy and breastfeeding as for other women. Ask your midwife or GP before adding a supplement; many pregnancy vitamins already contain some.
What doses did the sleep studies use?
Three small trials in older adults used 320, 500 and up to 729 mg a day; a 2025 trial used 250 mg as bisglycinate. Most of those are above the UK and EU lines for supplements. These are amounts studied, not advice.
Related Guides
- Best magnesium supplement in the UK · magnesium forms compared (UK)
- US dosage guide (US limits and labels) · side effects
Sources
- NHS. Vitamins and minerals: others (magnesium). Last reviewed August 3, 2020; read October 15, 2026.
- Public Health England. Government Dietary Recommendations (2016), Tables 5 and 6.
- Department of Health. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom (1991), Table 23.1: no increment in pregnancy, +50 mg a day while breastfeeding.
- EFSA. Dietary Reference Values for magnesium. EFSA Journal 2015;13(7):4186.
- EFSA / Scientific Committee on Food. Tolerable Upper Intake Levels for Vitamins and Minerals, 2006 (magnesium opinion 2001); EFSA summary, version 11, 2025.
- Expert Group on Vitamins and Minerals. Safe Upper Levels for Vitamins and Minerals, 2003 (archived copy).
- Regulation (EU) No 1169/2011 Annex XIII as retained in GB: nutrient reference values.
- US NIH Office of Dietary Supplements. Magnesium fact sheet for health professionals (medicines, US limits).
- Mah 2021, PubMed 33865376; Schuster 2025, PubMed 40918053; Barna 2021, PubMed 34719399; van der Schoot 2023, PubMed 37243443.