Quick answer
Under US law, a dietary supplement is a product taken by mouth to supplement the diet that contains at least 1 dietary ingredient, such as a vitamin, mineral, herb, amino acid or extract. It must be labeled as a dietary supplement and not presented as a conventional food. Congress set this definition in 1994.1,2
Key facts
- Dietary ingredients include vitamins, minerals, herbs and other botanicals, amino acids, dietary substances such as enzymes and live microbials, and concentrates, metabolites, constituents or extracts of these.1,2
- Supplements must be swallowed; topical and inhaled products are not supplements.2
- Forms include pills, tablets, capsules, gummies, softgels, liquids and powders, and even teas or bars when they are not presented as conventional food.2
- The label must say dietary supplement, or replace dietary with the ingredient or type, as in calcium supplement or herbal supplement.2,3
- In law, a dietary supplement is treated as a food for most purposes, not as a drug.1
- FDA does not approve supplements before they are sold; companies are responsible for their safety and for truthful labels.2,4
The legal definition, piece by piece
- A product, other than tobacco, intended to supplement the diet.1
- That contains one or more dietary ingredients.1
- Intended for ingestion, in a form such as a tablet, capsule, powder, softgel, gelcap or liquid.1,5
- Not represented as a conventional food or as the sole item of a meal or of the diet.1
- Labeled as a dietary supplement.1
The definition also leaves out articles approved as new drugs or licensed as biologics, or under substantial, public clinical investigation as drugs, unless they were sold as supplements or foods first.1,2
Two kinds of ingredient
FDA separates dietary ingredients, which are what the product is for, from other ingredients such as fillers, binders, excipients, preservatives, sweeteners and flavorings. The first group goes in the Supplement Facts panel, and anything not listed there goes in the Other Ingredients list.2
How supplements are regulated
FDA regulates supplements mostly after they reach the market. Firms do not need FDA approval for a product or its label, but they must make sure it is not adulterated or misbranded, follow good manufacturing practices for identity, purity, strength and composition, and register the facilities that make or hold them.2
One check comes before sale. A product with a new dietary ingredient, one not marketed in a supplement before October 15, 1994, needs a safety notification to FDA at least 75 days ahead, unless the ingredient is already in the food supply in a form that has not been chemically altered.2,5
FDA is generally responsible for safety, quality and labeling, and the Federal Trade Commission for advertising.2
Before you take one
FDA advises talking to a doctor, pharmacist or other health care professional before deciding to use a supplement, in part because some interact with medicines or other supplements. NCCIH adds that many supplements have not been tested in pregnant women, nursing mothers or children.2,4
Questions people ask
Is a dietary supplement a drug?
No. In law it is a kind of food. A product sold as a dietary supplement but represented for the treatment, prevention or cure of a specific disease meets the definition of a drug and is regulated as one.1,2
Does FDA approve dietary supplements?
No. By law FDA does not approve supplements or their labels before sale, apart from some claim types such as health claims. It inspects facilities, reviews new dietary ingredient notifications and acts against unsafe or mislabeled products.2
Are probiotics dietary supplements?
They can be. FDA lists live microbials, commonly called probiotics, among the dietary substances a supplement may contain.2
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Sources
- United States Code, Title 21, Section 321: Definitions (paragraph ff, dietary supplement). Legal Information Institute, Cornell Law School. Opened 2026-10-07.
- U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements. Content current as of August 27, 2026. Opened 2026-10-07.
- Code of Federal Regulations, Title 21, Section 101.3: Identity labeling of food in packaged form. Legal Information Institute, Cornell Law School (eCFR text). Opened 2026-10-07.
- National Center for Complementary and Integrative Health. Using Dietary Supplements Wisely. Opened 2026-10-07.
- U.S. Food and Drug Administration. New Dietary Ingredients in Dietary Supplements: Background for Industry. Content current as of February 9, 2023. Opened 2026-10-07.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.