Mineral Safety Quick Reference: Upper Levels, Interactions, Kidney Disease, Pregnancy and When to Seek Care

Urgent first

If a child (or anyone) has swallowed a mineral supplement and you are worried, call Poison Help at 1-800-222-1222 in the US, or 911 in an emergency. MedlinePlus says the Poison Help line can be called for any reason, 24 hours a day. [1] Iron is the main concern for children: iron overdose is particularly dangerous for children, and a severe overdose can happen if a child eats adult multivitamins, such as prenatal vitamins. [1] Symptoms can go away for a few hours and then return after a day or later, so do not wait for them. [1] Outside the US, see Poison Help by country.

Other warning signs that need prompt medical care:

• Low blood sodium (confusion, irritability, convulsions): MedlinePlus says that when sodium drops too much it can be a life-threatening emergency. [2]
• High blood potassium: there are often no symptoms, but chest pain, difficulty breathing, palpitations or a slow, weak or irregular pulse can occur, and very high levels need emergency treatment. [3]
• Black or bloody stools after swallowing iron are listed as symptoms of iron overdose. [1]

Upper levels at a glance

An upper level (UL) is the maximum level of total chronic daily intake of a nutrient (from all dietary sources) [4] which is not expected to pose a risk of adverse health effects. [4] It is a ceiling for healthy adults, not a target and not advice for any one person. The table shows what three sources publish. Amounts are in the units each source uses; a microgram (µg) is 1,000 times smaller than a milligram (mg). [5]

How to read the table

• The numbers differ by country and by method. Different bodies reviewed different evidence, so none of these figures is "the" limit. For a fuller comparison, see Mineral intake references compared. We did not read the US National Institutes of Health fact sheets (the page was blocked), so no US figures are shown here.
• Magnesium is a special case. Health Canada states that its figure represents intake from a pharmacological agent only and does not include food and water. [6] EFSA's figure likewise leaves out magnesium naturally present in foods and drinks. [4] Food magnesium is not the concern in these figures.
• "No UL" does not mean "no risk". EFSA notes that safe levels have more limited applications than upper levels. [4] Health Canada says sodium limits could not be set because of a lack of suitable data. [6]
• Elemental versus compound weight. US supplement labels must list the weight of the mineral itself, such as calcium, rather than the weight of the compound, such as calcium carbonate. [10] We did not check label rules outside the US for this page; see Mineral units explained.
• Health Canada's values are for normal, apparently healthy individuals eating a typical mixed North American diet. [6] People with medical conditions or regular medicines should ask a clinician or pharmacist.

Medicines and interactions

Never stop or change a prescribed medicine because of a supplement or this page. Ask a pharmacist. Some examples the sources document:

• Dietary supplements may interact with medications or pose risks if you have certain medical problems or are going to have surgery. [11]
• Some medicines might interfere with how the body absorbs calcium, and MedlinePlus says to tell your provider about all supplements and medicines. [12]
• High blood potassium can be caused by ACE inhibitors and angiotensin II receptor blockers (blood pressure medicines), potassium-sparing diuretics such as spironolactone, and extra potassium from salt substitutes or supplements. [13][3]
• High doses of iodine with anti-thyroid medicines can have an additive effect and could cause hypothyroidism. [14]
• Taking high doses of zinc reduces the amount of copper the body can absorb, which can lead to anaemia and weakening of the bones. [5]

For the full list, see the mineral and medicine interactions reference, spacing supplements and medicines and medication interactions.

Kidney disease

Damaged kidneys cannot remove phosphorus from the blood as well as healthy kidneys can. [15] Chronic kidney disease can also make it harder to remove potassium, so blood potassium can become very high. [15] MedlinePlus says side effects from high magnesium intake are not common, except in people with significantly reduced kidney function. [16] If you have kidney disease, it is important to talk to your provider before taking potassium supplements. [13] A dietitian or health care professional can help with food choices. [15] Details: Minerals, supplements and kidney disease.

Pregnancy, breastfeeding and children

Many dietary supplements have not been tested in pregnant women, nursing mothers or children. [11] Pregnant or breastfeeding readers should ask their midwife, doctor or pharmacist before adding any mineral product. See Minerals in pregnancy and Iron overdose and child safety. The NHS says very high doses of iron can be fatal, particularly if taken by children, so supplements should be kept out of reach. [8]

Liver, iron overload and surgery

• Iron overload. In hemochromatosis too much iron builds up in the body. [17] The inherited form affects the body's ability to control how much iron is absorbed. [18] Anyone told they have too much iron should ask their clinician before using iron or multivitamin products containing iron.
• Liver and kidneys. The NHS lists damage to the liver and kidneys (if taken for a long time) among effects of high copper doses. [5] For liver conditions, see Liver safety and supplements.
• Before surgery. Certain dietary supplements may increase the risk of bleeding or affect your response to anesthesia, so tell your care team about everything you take well ahead. [11] Proper evidence not found, in the pages we read, for which individual minerals matter most before an operation. See Supplements before surgery.

Common reactions, by mineral

• Iron: side effects of high doses (over 20 mg) include constipation, nausea, vomiting and stomach pain. [8]
• Magnesium: high doses (more than 400 mg) for a short time can cause diarrhoea. [5]
• Calcium: more than 1,500 mg a day could lead to stomach pain and diarrhoea, and higher amounts over a long period raise the risk of kidney stones in some people. [7][12]
• Zinc: large amounts may cause diarrhea, abdominal cramps and vomiting; nasal sprays and gels containing zinc may cause loss of the sense of smell. [19]
• Selenium: too much causes selenosis, which in its mildest form can lead to loss of hair and nails. [5]
• Iodine: high doses for long periods could change the way the thyroid gland works. [9]
• Calcium and milk-alkali syndrome: too much calcium in the diet is one cause of high blood calcium. [20]

More detail: Mineral side effects quick reference.

Product quality

The label may not match the bottle. NCCIH notes that what is on the label may not be what is in the product. [11] See Quality testing and certifications. Before starting any mineral, use the safety checklist and take the questions for your clinician or pharmacist with you.

This page is general information, not medical advice. A clinician or pharmacist who knows your medicines, kidney function and health history decides what is right for you.