Vitamin Toxicity: Which Vitamins Have Upper Limits and What Happens With Too Much

If someone has swallowed a lot of vitamins

Call Poison Help at 1-800-222-1222 (US) or call 911 if the person collapses, has a seizure, has trouble breathing or cannot be woken. [1] For a child, read Vitamin overdose in children and accidental ingestion first. For other countries see Poison Help by country. This page is information only and does not replace a poison center, a pharmacist or a clinician.

The short answer

Yes, you can take too many vitamins, and "too much" mostly happens with supplements and fortified products rather than ordinary food. Some vitamins have an official upper limit. Some do not, and for those the sources say the data are lacking, which is not the same as proof that any amount is safe. [2][3]

What an upper limit is, and is not

EFSA (the European Food Safety Authority) defines a tolerable upper intake level (UL) as the highest chronic daily intake from all sources that is not expected to pose a risk of harm. [4] It is a ceiling for planning, not a target. See RDA, AI, DV and UL for how it differs from a recommended amount.

Official upper limits for adults

These are published reference values, not instructions. Different bodies reach different numbers because they weigh the evidence differently, and units differ (mcg RAE and mcg RE are not converted here).

The UK NHS gives a different kind of guidance: amounts "unlikely to cause any harm" in supplements, for example under 1,000 mg for vitamin C, 1 mg or less for vitamin K and 540 mg (800 IU) or less for vitamin E. [14][2][15] For vitamin B6 it says not to exceed 10 mg a day in supplements unless a doctor advises. [3] These are advice thresholds, not the same thing as the ULs above. Neither Health Canada nor EFSA values here replace what a clinician advises for you.

Water-soluble does not mean harmless

Extra water-soluble vitamins are mostly passed in urine, [16] yet some cause real harm. The NHS says 200 mg or more of vitamin B6 a day can cause numbness and loss of feeling in the arms and legs, which in a few cases was permanent. [3] A case report described nerve symptoms and a high blood B6 level in a man taking a multivitamin with 6 mg, below EFSA's 12 mg limit; one case cannot show cause, but it is why labels matter. [17] Too much niacin can raise blood sugar and damage the liver. [18]

Fat-soluble vitamins build up

Vitamins A, D, E and K are stored in the body. [16] Toxicity from vitamin D almost always comes from too many supplements, not sun or food. [8] Case reports of vitamin D poisoning included manufacturing errors and dosing mistakes. [19] For retinol, a review of 259 case reports found water-miscible, emulsified and solid forms about 10 times as toxic as oil-based ones. [20] The NHS warns that more than about 1.5 mg of vitamin A a day over many years may weaken bones. [21] Beta-carotene from food is not linked to harm, but see the smoker warning above. [7]

Who should be extra careful

• Pregnancy: large vitamin A doses can cause birth defects, and the NHS advises avoiding liver and liver products in pregnancy. [6][21] See Vitamins in pregnancy.
• Children: upper limits are lower for children; the NHS lists 50 mcg (2,000 IU) of vitamin D for ages 1 to 10 and 25 mcg (1,000 IU) for infants under 12 months. [22]
• Kidney or liver disease, surgery, medicines: these change how vitamins are handled. See Vitamins and kidney or liver disease, Vitamins before surgery and Medication interactions.
• Stacking: a multivitamin, a "hair" product and a fortified drink can each carry the same vitamin. Add up labels and ask a pharmacist. See Amounts and duplicate ingredients.

What this page cannot tell you

Proper evidence not found: no single safe amount applies to everyone. Sources searched were Health Canada, EFSA, NHS and MedlinePlus pages. NIH Office of Dietary Supplements pages could not be read, so US National Academies limits are not quoted directly. Ask a clinician or pharmacist about your own situation, and check product quality at Quality testing and certifications.