Mineral Toxicity: Which Minerals Have Upper Limits and What Happens With Too Much
Which minerals have official upper limits from Health Canada and EFSA, how those differ, what the NHS and MedlinePlus report with too much, and why more is not better.
Content last updated . This page has not been medically reviewed.
Urgent first
If someone, especially a child, has swallowed a large amount of any mineral supplement, call 911 or Poison Help at 1-800-222-1222 in the US; MedlinePlus says the Poison Help line is free and can be called for any reason, 24 hours a day. [1] For other countries see Poison help by country. Iron is the best-documented child emergency; see Iron overdose and child safety. Do not wait for symptoms.What an upper limit is
EFSA (the European Food Safety Authority) defines a Tolerable Upper Intake Level (UL) as the maximum level of total chronic daily intake of a nutrient from all dietary sources which is not expected to pose a risk of adverse health effects. [2] It is a ceiling for long-term intake in the general population, not a target and not a dose. Where data are insufficient, EFSA gives a "safe level of intake" instead, which it says has more limited uses than a UL. [2] Health Canada's tables say their reference values are for normal, apparently healthy people eating a typical mixed North American diet, and that an individual may need values tailored to health or lifestyle. [3]Three things to keep in mind. First, a UL may cover food plus supplements, or supplements only: Health Canada's footnote says the magnesium UL represents intake from a pharmacological agent only and does not include intake from food and water. [3] Second, countries differ. Third, people with kidney disease, children, older adults and people who are pregnant or breastfeeding may need different advice from a clinician. Evidence labels used here: official reference value and regulator or health-service guidance.
Upper levels and safe levels for adults
Units are as printed by each source. 1 mg equals 1,000 µg, as the NHS notes when it says a microgram is 1,000 times smaller than a milligram. [4] Whether a figure is elemental mineral or compound weight is not stated for every row in the pages we read, so compare units with care.| Mineral | Health Canada UL, adults (2025 page) | EFSA UL or safe level, adults (2025 overview) | NHS (UK) guidance (supplement amounts unless stated; pages reviewed 2020) |
|---|---|---|---|
| Calcium | 2,500 mg/day (ages 19-50); 2,000 mg/day (51 and over) | UL 2,500 mg/day | 1,500 mg a day or less unlikely to cause harm |
| Iron | 45 mg/day | No UL; safe level of intake 40 mg/day | 17 mg a day or less unlikely to cause harm |
| Zinc | 40 mg/day | UL 25 mg/day | Do not take more than 25 mg a day unless advised by a doctor |
| Copper | 10,000 µg/day | UL 5 mg/day | 10 mg or less a day from food, water and supplements |
| Magnesium | 350 mg/day, supplemental only | UL 250 mg/day from readily dissociable salts and oxide in supplements, water or added to foods | 400 mg or less a day from supplements |
| Manganese | 11 mg/day | No UL; safe level of intake 8 mg/day | 4 mg or less a day; 0.5 mg or less for older people |
| Selenium | 400 µg/day | UL 255 µg/day | 350 µg or less a day |
| Iodine | 1,100 µg/day | UL 600 µg/day | 0.5 mg or less a day |
| Phosphorus | 4,000 mg/day (19-70); 3,000 mg/day (over 70) | No adequate data for a UL | 250 mg or less a day on top of diet |
| Potassium | No UL (ND) | No adequate data for a UL | 3,700 mg or less a day of supplements; older people should not take potassium supplements unless advised |
| Sodium | No UL (ND) | No adequate data for a UL | No more than 6 g of salt (2.4 g sodium) a day |
| Fluoride | 10 mg/day | Adults: UL not defined; safe level of intake 3.3 mg/day | No amount given on the NHS fluoride page we read |
| Chromium | No UL (ND) | No adequate data for a UL | 10 mg or less a day from food and supplements |
| Molybdenum | 2,000 µg/day | UL 0.6 mg/day | No figure given |
Sources: Health Canada [3]; EFSA [2]; NHS [5][6][7][4]. Health Canada's 2025 table also lists other values for pregnancy and breastfeeding (for example phosphorus 3,500 mg/day in pregnancy at ages 19-50) and for children; read the source for those groups. [3] NHS "unlikely to cause harm" amounts are guidance from the UK Department of Health and Social Care as reported by the NHS, not Daily Values, not targets and not personal advice. We did not read US NIH Office of Dietary Supplements pages for this table because they could not be opened, so US Institute of Medicine/NASEM figures are not quoted from memory. Check the primary US source for US-specific figures.
Why do the numbers differ? The sources set limits at different times, for different populations and with different safety margins, and some count only supplements. Health Canada notes that ULs could not be established for chromium, and that this does not mean there is no potential for adverse effects from high intakes. [3]
What is reported with too much
| Mineral | Reported with excess | Source |
|---|---|---|
| Calcium | Doses above 1,500 mg a day could lead to stomach pain and diarrhoea (NHS). Higher amounts over a long period raise the risk of kidney stones in some people (MedlinePlus). | [5][8] |
| Iron | Over 20 mg: constipation, feeling or being sick, stomach pain. Very high doses can be fatal, particularly in children. | [6] |
| Zinc | High doses reduce the copper the body can absorb, which can lead to anemia and weakening of the bones (NHS). MedlinePlus lists diarrhea, abdominal cramps and vomiting, long-term copper, iron or magnesium deficiency, and loss of smell with zinc nasal sprays and gels. | [4][9] |
| Copper | Stomach pain, sickness, diarrhoea, and liver and kidney damage if taken for a long time (NHS). In large amounts copper is poisonous (MedlinePlus). | [4][10] |
| Magnesium | More than 400 mg for a short time can cause diarrhoea (NHS). MedlinePlus says side effects from high intake are not common except in people with significantly reduced kidney function. | [4][11] |
| Manganese | High doses for long periods might cause muscle pain, nerve damage, fatigue and depression. | [4] |
| Selenium | Selenosis, which in its mildest form can lead to loss of hair and nails. | [4] |
| Iodine | High doses for long periods could change the way the thyroid works (NHS). Very high intake can reduce thyroid function (MedlinePlus). | [7][12] |
| Phosphorus | Short-term diarrhea or stomach pain; long-term high doses can reduce calcium in the body and make fractures more likely (NHS). | [4] |
| Potassium | Stomach pain, feeling sick and diarrhoea (NHS). Too much potassium in the blood (hyperkalemia) may cause abnormal and dangerous heart rhythms; poor kidney function and some blood pressure medicines are common causes (MedlinePlus). | [4][13] |
| Sodium (salt) | Too much salt is linked to high blood pressure. | [4] |
| Fluoride | Too much while teeth are forming can cause dental fluorosis, faint white marks on the teeth; the NHS describes it as usually mild. | [14] |
| Chromium | There is not enough evidence to know the effects of high daily doses. | [4] |
| Molybdenum | There is some evidence that supplements might cause joint pain. | [4] |
Who is more at risk
- Kidney disease. Potassium, phosphorus and magnesium can build up; see Minerals, supplements and kidney disease.
- Children and infants. Limits are lower for children; Health Canada and EFSA print age-specific values. [3][2]
- Older adults. The NHS says older people may be more sensitive to manganese and should not take potassium supplements unless advised. [4]
- Pregnancy and breastfeeding. Reference values differ for these groups in the sources; ask a clinician before using mineral products. See Pregnancy and breastfeeding.
- Medicines. Some minerals interact with medicines; see Mineral and medicine interactions.
- Before surgery. Tell the surgical team about every supplement; see Supplements before surgery.
Intakes add up
A multivitamin, a mineral formula, fortified foods and a separate mineral product can each contribute. See Amounts and duplicate ingredients and Multivitamins and multiminerals. Product quality varies; see Quality testing and certifications. Water-soluble or "natural" does not mean harmless, and more is not better. Talk to a clinician or pharmacist before using amounts near any limit.What we could not find
The US NIH Office of Dietary Supplements pages could not be read, so US upper levels are not quoted here. Proper evidence not found, in the sources we read, for a UL for potassium, sodium or chloride. We searched the Health Canada and EFSA tables and the NHS and MedlinePlus pages named above.Frequently asked questions
Which minerals have an official upper limit?
In the tables we read, both Health Canada and EFSA list a UL for calcium, zinc, copper, magnesium (supplemental), selenium, iodine, molybdenum and several others, but not for potassium, sodium or chromium. [3][2]
Why do Health Canada and EFSA give different numbers?
The sources do not explain every difference. They are separate reviews that set limits for different populations and at different times, and some limits apply only to supplements, such as the magnesium limits. [3][2]
Is it safe to take a mineral supplement up to its upper limit?
A UL is a ceiling for long-term total intake, not a target. A clinician or pharmacist can say what is right for you, particularly if you have kidney or liver disease, are pregnant or take medicines. [2]
Does a limit count food as well as supplements?
It depends on the source. EFSA defines its UL as total intake from all dietary sources, while Health Canada's magnesium UL excludes magnesium from food and water. [2][3]
What should I do after a suspected overdose?
Call Poison Help (US 1-800-222-1222) or 911. MedlinePlus says you can call for any reason. [1]
References
- MedlinePlus (US National Library of Medicine). Iron overdose (review date 14 October 2025). MedlinePlus (US National Library of Medicine). Iron overdose (review date 14 October 2025). Read 2026-10-23.
- EFSA. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA NDA Panel, version 11 (August 2025). EFSA. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA NDA Panel, version 11 (August 2025). Read 2026-10-23. Table text extracted from the PDF file.
- Health Canada. Dietary reference intakes tables: Reference values for elements (page details 2025-11-19). Health Canada. Dietary reference intakes tables: Reference values for elements (page details 2025-11-19). Read 2026-10-23.
- NHS. Vitamins and minerals: Others (chromium, copper, magnesium, manganese, molybdenum, phosphorus, potassium, selenium, salt, zinc; page last reviewed 3 August 2020). NHS. Vitamins and minerals: Others (chromium, copper, magnesium, manganese, molybdenum, phosphorus, potassium, selenium, salt, zinc; page last reviewed 3 August 2020). Read 2026-10-23.
- NHS. Vitamins and minerals: Calcium (page last reviewed 3 August 2020). NHS. Vitamins and minerals: Calcium (page last reviewed 3 August 2020). Read 2026-10-23.
- NHS. Vitamins and minerals: Iron (page last reviewed 3 August 2020). NHS. Vitamins and minerals: Iron (page last reviewed 3 August 2020). Read 2026-10-23.
- NHS. Vitamins and minerals: Iodine (page last reviewed 3 August 2020). NHS. Vitamins and minerals: Iodine (page last reviewed 3 August 2020). Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Calcium in diet. MedlinePlus (US National Library of Medicine). Calcium in diet. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Zinc in diet. MedlinePlus (US National Library of Medicine). Zinc in diet. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Copper in diet. MedlinePlus (US National Library of Medicine). Copper in diet. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Magnesium in diet. MedlinePlus (US National Library of Medicine). Magnesium in diet. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Iodine in diet. MedlinePlus (US National Library of Medicine). Iodine in diet. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Potassium in diet. MedlinePlus (US National Library of Medicine). Potassium in diet. Read 2026-10-23.
- NHS. Fluoride. NHS. Fluoride. Read 2026-10-23.