Magnesium Intake Levels: Official Figures by Age and Country and the Supplement Upper Limit
Official magnesium reference intakes by age, sex and pregnancy in the US, EU and UK, and the supplement upper limits that apply only to magnesium from supplements and medicines.
Content last updated . This page has not been medically reviewed.
Quick answer
There is no single "right" magnesium number. Published adult reference intakes range from 270 to 420 mg a day depending on the body, sex and age, and the upper limits for supplements differ between countries (250, 350 and "400 or less" mg a day in the sources below). [1][2][3][4] The upper limit applies only to magnesium from supplements and medicines, not from food. [3] These are group reference values, not personal doses; a clinician or pharmacist decides what suits a person.
How the sources define the terms
- Recommended Dietary Allowance (RDA): the average daily intake enough to meet the needs of nearly all (97 to 98%) healthy people. Adequate Intake (AI): set when evidence is not enough for an RDA. [2]
- EFSA (EU): for magnesium it publishes Adequate Intakes, not Population Reference Intakes. [5]
- Upper limit (UL): Health Canada says the magnesium UL represents intake from a pharmacological agent only, not food and water. [6]
- Daily Value (DV): a US labeling reference; for magnesium FDA lists 420 mg for adults and children over 4, 400 mg for pregnant and lactating women and 80 mg for children 1-3. [3]
Reference intakes by group
Amounts are mg of magnesium a day. Bodies use different age bands, so rows are not interchangeable.| Source and year | Group | Amount |
|---|---|---|
| US, via MedlinePlus (reviewed 2025) | Infants 0-6 months (AI); 6-12 months (AI) | 30; 75 [2] |
| Children 1-3; 4-8; 9-13 years | 80; 130; 240 [2] | |
| Ages 14-18, boys; girls | 410; 360 [2] | |
| Men 19-30; 31 and over | 400; 420 [2] | |
| Women 19-30; 31 and over | 310; 320 [2] | |
| Pregnancy 14-18; 19-30; 31-50 | 400; 350; 360 [2] | |
| Breastfeeding | 310 to 360 [2] | |
| EFSA (EU), Adequate Intakes, 2017 | Infants 7-11 months; children 1-2; 3-9 years | 80; 170; 230 [5] |
| Ages 10-17, males; females | 300; 250 [5] | |
| Adults 18 and over, men; women | 350; 300 [5] | |
| Pregnancy; lactation | 300; 300 [5] | |
| NHS (UK), page reviewed 2020 | Adults 19-64, men; women | 300; 270 [1] |
The NHS page's own review date has passed, so check for updates. Health Canada's 2025 table was read through a web-fetch tool, and its adult figures matched the US RDAs above. [6]
Upper limits for supplemental magnesium
| Body and year | Group | Upper limit (mg a day) |
|---|---|---|
| US Institute of Medicine (1997), as described by FDA | Ages over 8, including pregnant and lactating women | 350 [3] |
| Children 1-3; 4-8 years | 65; 110 [3] | |
| Health Canada (2025) | Ages 9 and over, including pregnancy and lactation | 350 [6] |
| Children 1-3; 4-8 years | 65; 110 [6] | |
| EFSA, Scientific Committee on Food (2001 opinion) | Adults, pregnant and lactating women, children from 4 years; readily dissociable salts and magnesium oxide | 250 [4] |
| Children 1-3 years | No UL could be established [4] | |
| NHS (UK) | Adults, from supplements | 400 or less is unlikely to cause harm [1] |
The NHS also says there is not enough evidence to say what high doses taken for a long time might do. [1]
What the limits are based on
Both the US and EU limits rest on diarrhea, not on organ damage. FDA says the Institute of Medicine took diarrhea as the endpoint, found the lowest observed effect at 360 mg a day from non-food sources, and set 350 mg. [3] EFSA's committee found mild diarrhea in a small percentage of adults at about 360 to 365 mg and no laxative effect up to 250 mg a day. [4] EFSA also said toxic high blood magnesium was seen only at oral doses above 2,500 mg in the cases it reviewed, and named severely reduced kidney function as a risk factor. [4] That figure is not a target.Typical intakes
In 2015-2016 US survey data cited by FDA, mean magnesium intake from foods and beverages was 289 mg a day for people aged 2 and over, excluding supplements. [3] A reference intake is for planning, not a deficiency cut-off; see Magnesium deficiency.Frequently asked questions
How much magnesium does an adult need according to official bodies?
Between 270 and 420 mg a day depending on the body, sex and age: for example the NHS 300 mg (men) and 270 mg (women) aged 19-64, EFSA 350 and 300 mg for adults, and the US RDA of 420 and 320 mg for adults 31 and over. [1][5][2]
Does the upper limit include magnesium from food?
No. The upper limits apply only to magnesium from supplements or medicines. [3][6]
Why do the US and EU upper limits differ?
They come from different expert committees and years: 350 mg (US Institute of Medicine) and 250 mg (EFSA, 2001 opinion), both based on diarrhea. [3][4]
What is the upper limit for children?
The US and Canada give 65 mg for ages 1-3 and 110 mg for ages 4-8 for supplemental magnesium; EFSA set none for ages 1-3. [3][6][4]
Does the Daily Value on a label equal what I should take?
No. It is a US labeling reference, 420 mg for adults and children over 4. [3]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Limits and uncertainty
- Supplement labels declare elemental magnesium, not the whole compound's weight. [3] See Magnesium and Magnesium forms compared.
- The US and EU limits were set from different evidence and do not agree, and some are decades old.
- Limits for magnesium from medicines such as laxatives are a separate matter; see the laxative page.
Safety and who should ask first
- Kidney disease: high blood magnesium mostly occurs in people with kidney failure. [7] See Minerals and kidney disease.
- Medicines: ask a pharmacist about timing; see Spacing supplements and medicines.
- Pregnancy, breastfeeding and children: talk to a clinician first. NCCIH notes many supplements have not been tested in pregnant women, nursing mothers or children. [8]
- Check label amounts with Reading supplement labels.
References
- NHS (UK). Page last reviewed 3 August 2020 (scheduled review date has passed). NHS, Vitamins and minerals: Others (magnesium, phosphorus, potassium, salt). Read 2026-10-22.
- MedlinePlus (US National Library of Medicine). Review date 1/21/2025. MedlinePlus Medical Encyclopedia, Magnesium in diet. Read 2026-10-22.
- US Food and Drug Administration, letter responding to a qualified health claim petition (Docket FDA-2016-Q-3770); the letter cites sources accessed in 2021. FDA letter on a qualified health claim for magnesium and reduced risk of high blood pressure. Read 2026-10-22.
- European Food Safety Authority (EU), compendium of Scientific Committee on Food opinions (2006); the magnesium opinion was expressed on 26 September 2001. EFSA / Scientific Committee on Food, Tolerable Upper Intake Levels for Vitamins and Minerals. Read 2026-10-22.
- European Food Safety Authority (EU), version 4, September 2017. EFSA, Overview on Dietary Reference Values for the EU population (September 2017). Read 2026-10-22.
- Health Canada, Dietary reference intakes tables: reference values for elements; page date modified 2025-11-19 (read through a web-fetch tool). Health Canada, Dietary reference intakes tables: Reference values for elements. Read 2026-10-22.
- MedlinePlus (US National Library of Medicine). MedlinePlus, Magnesium Blood Test. Read 2026-10-22.
- National Center for Complementary and Integrative Health (US), last updated January 2019. NCCIH, Using Dietary Supplements Wisely. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.