28 February 2018Is Your Vitamin Mineral Supplement Giving You Too Much of a Good Thing?

Can you get too much of a good thing? Well, yes, if it concerns vitamins or minerals. Many of us have the mistaken assumption that if we need a little of something for health, then more is better. But getting too much of certain vitamins or minerals could be harmful. Of particular concern is getting a megadose or very large dose of a vitamin or mineral from a supplement.

Tolerable Upper Limit (UL)

According to the National Institutes of Health's Office of Dietary Supplements, the Tolerable Upper Limit is the maximum daily intake unlikely to cause adverse health effects. Not all vitamins and minerals have an UL given lack of data or no evidence of harm at high intakes.

To find the UL for a nutrient in MyNetDiary, go to Plan section, select Nutrient Targets, find the vitamin or mineral of interest, tap the 3-dot icon to the right of the name, and then select the "Set Target" option to view recommended intake as well as the UL. If the nutrient has an UL, it will be listed there.

If you take vitamin or mineral supplements, please check the amount of each vitamin and mineral in your supplement against the UL value. Supplement manufacturers do not do this for you - they are not required to list the UL nor are they required to limit the amount of a nutrient to its UL. Many supplements contain well over the UL. Labels typically list the actual nutrient content as well as the % Daily Value (%DV) - a value used specifically for food labels to help consumers compare intake against a generic daily goal. The Daily Value for a nutrient could be higher or lower than a person's Recommended Dietary Allowance (RDA) for their age and sex group.

Vitamins & Minerals

The table below includes vitamins and minerals you can track in MyNetDiary and for which there is an UL. The water-soluble vitamins are listed first (folate, niacin, and vitamins B6 and C), then the fat-soluble vitamins (vitamins A, D, and E), and lastly, the minerals (calcium, copper, iron, magnesium, manganese, and phosphorus). Because supplements never include this on their labels, I calculated the percentage of the UL value for each nutrient against it's Daily Value. This percentage is represented in the last column as "% UL / Daily Value."

Rethink your supplement choice if the content of one or more nutrients is higher than the UL or if the %DV on the package is higher than the % UL / Daily Value listed here. The exception would be if you have been prescribed a high-dose vitamin or mineral supplement by your healthcare provider to correct a nutrient deficiency or to manage a chronic disease. Contact your healthcare provider, pharmacist, or registered dietitian if you are not sure if your supplement amount is safe or if you have more questions about supplements.

Nutrient UL Adults Daily Value* % UL / Daily Value
Folate 1000 mcg 400 mcg 250%
Niacin 35 mg 20 mg 175%
Vit B6 100 mg 2 mg 5000%
Vit C 2000 mg 60 mg 3333%
Vit A 10,000 IU (3000 mcg) 5000 IU 200%
Vit D 4000 IU (100 mcg) 400 IU 1000%
Vit E 1490 IU (1000 mg) 30 IU 4967%
Calcium 2500 mg age 19-50 yr
2000 mg age > 50 yr
1000 mg 250% age 19-50 yr
200% age > 50 yr
Copper 10,000 mcg 2000 mcg 500%
Iron 45 mg 18 mg 250%
Magnesium 350 mg 400 mg 87.5%
Manganese 11 mg 2 mg 550%
Phosphorus 4000 mg age 19-70 yr
3000 mg age > 70 yr
1000 mg 400% age 19-70 yr
300% age > 70 yr

* The Daily Value listed here comes from the current food label. If you wish to see the updated Daily Values that are used for the new food label (required by 2020), see the Federal Register / Vol. 81, No. 103 / Friday, May 27, 2016 / Rules and Regulations, pages 241 - 242 of the PDF document (or pages 33982 - 33983 of the Federal Register document).

Supplement Form vs. Food Source

For certain nutrients, it is the synthetic form found in supplements or fortified food sources that can cause risk in high doses. Nutrients coming from natural food sources are rarely the cause of nutrient toxicity. Please see below for more detail about this issue of supplement form vs. food source.


Regular intake above the UL could result in adverse health effects, especially in people who take prescription medications for cancer (methotrexate), epilepsy (phenytoin), or ulcerative colitis (sulfasalazine). Risk is from the synthetic form found in fortified foods (e.g. fortified breakfast cereals) and vitamin supplements.


Regular intake above the UL could result in adverse health effects such as flushing, nausea, vomiting, diarrhea, rash, higher blood glucose, and liver damage. Risk is from the synthetic form found in supplements and fortified foods. If you take prescription niacin, share symptoms with your doctor.

Vitamin A

Consuming more than the UL can cause adverse health effects such as birth defects and liver disease. The UL for vitamin A applies only to preformed vitamin A (retinol) found in animal sources (e.g. liver) and supplements. Beta-carotene or plant-sources of vitamin A is not considered a risk -so don't worry if your high vitamin A content is coming from fruits and vegetables.

Vitamin E

Regular intake above the UL could result in excessive bleeding - especially if you take a blood thinner such as warfarin. The risk is limited to the synthetic form (alpha-tocopherol) found in supplements and fortified foods. There is no risk from natural food sources such as vegetable oils, whole grains, nuts, seeds, and wheat germ.


Are you surprised that the UL is lower than the Daily Value? This is not an error and the reason is simple. The tolerable upper limit (UL) applies only to magnesium coming from supplements and medications. Too much magnesium from supplements and medications can cause adverse health effects such as diarrhea, nausea, and cramping. But the good news is that there is no UL for magnesium that comes from food or water.

More Resources


Food and Nutrition Board, Institute of Medicine, National Academies:
Dietary Reference Intakes (DRIs): Tolerable Upper Intake Levels for Vitamins and Minerals

MyNetDiary Blog:
Do Vegans and Vegetarians Need Supplements?
Multivitamins May Not Be Your Friend
Calcium: Get Enough But Not Too Much!

National Institutes of Health:
National Center for Complementary and Integrative Health

National Institutes of Health, Office of Dietary Supplements:
Dietary Supplements: What You Need to Know
Dietary Supplement Fact Sheets
Katherine Isacks, MPS, RD, CDE
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Disclaimer: The information provided here does not constitute medical advice. If you are seeking medical advice, please visit your healthcare provider or medical professional.


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