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Dietary and Herbal Supplements

Beard Man Choosing Supplement In Drugstore

Federal law defines dietary supplements as products that: 

  • You take by mouth (such as a tablet, capsule, powder, or liquid). 
  • Are made to supplement the diet.
  • Have one or more dietary ingredients, including vitamins, minerals, herbs or other botanicals, amino acids, enzymes, tissues from organs or glands, or extracts of these. 
  • Are labeled as being dietary supplements.

Herbal supplements—sometimes called botanicals—are a type of dietary supplement containing one or more herbs. 

The amount of scientific evidence on dietary supplements varies widely—there is a lot of information on some and very little on others. If you’re considering using a dietary supplement, it’s important to keep the following in mind: 

  • Supplements you buy from stores or online may differ in important ways from products tested in research studies. 
  • Dietary supplements may interact with your medications or pose risks if you have certain medical problems or are going to have surgery. 
  • Many dietary supplements haven’t been tested in pregnant women, nursing mothers, or children. 
  • What’s listed on the label of a dietary supplement may not be what’s in the product. For example, some products marketed for weight loss, sexual enhancement, or bodybuilding have been found to contain prescription drugs not allowed in dietary supplements or other ingredients not listed on the label, and some of these ingredients may be unsafe. 
  • Rules for manufacturing and distributing dietary supplements are less strict than those for prescription or over-the-counter drugs. Although the U.S. Food and Drug Administration (FDA) requires that companies submit safety data about any new ingredient not sold in the United States in a dietary supplement before 1994, the FDA is not authorized to review dietary supplements for safety and effectiveness before they are marketed.
  • In 2023, the FDA launched the Dietary Supplement Ingredient Directory, a webpage where the public can look up ingredients used in products marketed as dietary supplements and find what the FDA has said about that ingredient, as well as whether the agency has taken any action with regard to the ingredient.

For More Information

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 1-888-644-6226

Telecommunications relay service (TRS): 7-1-1


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Know the Science

NCCIH and the National Institutes of Health (NIH) provide tools to help you understand the basics and terminology of scientific research so you can make well-informed decisions about your health. Know the Science features a variety of materials, including interactive modules, quizzes, and videos, as well as links to informative content from Federal resources designed to help consumers make sense of health information.

Explaining How Research Works (NIH)

Know the Science: How To Make Sense of a Scientific Journal Article

Understanding Clinical Studies (NIH)


A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed.


Office of Dietary Supplements (ODS), National Institutes of Health (NIH)

ODS seeks to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, supporting research, sharing research results, and educating the public. Its resources include publications (such as Dietary Supplements: What You Need To Know) and fact sheets on a variety of specific supplement ingredients and products (such as vitamin D and multivitamin/mineral supplements).

Dietary Supplements in the Time of COVID-19


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This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.

Last Updated: February 2020