Quality, Labels & Product Selection
How to judge herbal product quality and labels: plant name and part, extracts, testing, contamination and what a quality claim can and cannot tell you.
Content last updated . This page has not been medically reviewed.
Safety first. Natural products can cause side effects and interact with medicines. Read herb safety and interactions before you use anything on this page.
Quality is two questions, and neither is about whether it works
When people ask about herbal supplement quality, they usually mean two things. Is the right plant, and the right part of it, in the product? And is what is in the product what the label says? A third question, whether the herb helps or is safe for you, is separate. A well-made product can still interact with a medicine, and a certified product can still be the wrong choice for your health.The National Center for Complementary and Integrative Health (NCCIH, part of the US National Institutes of Health) notes that supplements bought in stores or online may differ in important ways from the products tested in studies. [1] That is why a study result for "ginkgo" or "milk thistle" does not automatically carry over to the bottle on a shelf.
What the rules say, and what they do not
In the US, NCCIH states that manufacturers are required to produce dietary supplements in a quality manner, make sure they do not contain contaminants or impurities, and label them accurately. [1] The FDA does not test dietary supplements before they are sold to consumers. [2] NCCIH adds that the FDA can act against adulterated or misbranded supplements only after a product is on the market. [1] MedlinePlus says herbal medicines do not have to go through the testing that drugs do. [3]Rules differ by country. England's NHS advises checking that a herbal medicine carries a traditional herbal registration (THR) mark and a product code from the Medicines and Healthcare products Regulatory Agency (MHRA). [4] For how the US system works in more detail, see How Supplements Are Regulated.
A plain checklist for reading a herbal label
| What to look at | Why it matters | Where to read more |
|---|---|---|
| Scientific name (genus and species) | Common names can point to different plants | More about Scientific name (genus and species) → |
| Plant part (leaf, root, seed...) | Parts of one plant can differ in safety | More about Plant part (leaf, root, seed...) → |
| Form and extract details | A result for one extract does not transfer to another form | More about Form and extract details → |
| "Standardized to..." wording | Describes one compound, not benefit or purity | More about "Standardized to..." wording → |
| Other ingredients and added herbs | Blends and fillers change what you are taking | More about Other ingredients and added herbs → |
| Testing or certification claims | Show something about a batch, not about benefit | More about Testing or certification claims → |
Why the plant and the part matter: three documented examples
- Chamomile. NCCIH notes there are two types, German and Roman chamomile, and its fact sheet focuses on German chamomile. [5]
- **Ginkgo (Ginkgo biloba).** The leaf, usually as an extract, is the most common form; fresh ginkgo seeds are toxic when eaten. [6]
- **Black cohosh (Actaea racemosa).** NCCIH says some commercial black cohosh products have been found to contain the wrong herb. [7]
"Standardized", "verified", "certified"
NCCIH warns that a manufacturer's use of the term "standardized" (or "verified" or "certified") does not necessarily guarantee product quality or consistency. [1] Details are on the standardization page and the third-party testing page.Frequently asked questions
Does "standardized" mean a better product?
Not necessarily. NCCIH says the word does not necessarily guarantee product quality or consistency. [1]
If a label lists a scientific name, is the product the right plant?
The name is the starting point, but the sources we read describe cases where products contained other herbs not listed on the label, for example some goldenseal and black cohosh products. [10] [7]
Does the FDA check herbal supplements before sale?
The FDA states that it does not test dietary supplements before they are sold to consumers. [2]
Can I tell quality from the price or a "natural" claim?
We did not find a source that links price or the word "natural" to quality. NCCIH says "natural" does not always mean "safe". [1]
Where can I check if a herbal product is licensed?
In England, the NHS points to the THR mark and an MHRA product code on the packaging. [4] In the US, ask a pharmacist; see the labels guide.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Documented quality problems (with the limits of each finding)
| Product studied | What the source found | Limits |
|---|---|---|
| Milk thistle supplements (Silybum marianum) | NCCIH says some products had silymarin amounts substantially different from the label or were contaminated with pesticides, microorganisms or mycotoxins. [8] A study of 26 products bought in the US and Czech markets in 2016-2017 found large differences in silymarin content. [9] | One product type; a small sample |
| Goldenseal supplements (Hydrastis canadensis) | NCCIH says some products contain other herbs or ingredients not on the label, in addition to or instead of goldenseal. [10] A metabolomics study of 35 products found some came from a non-goldenseal species or a mixture of plant materials. [11] | Not every product; the study did not say which share is affected overall |
| St John's wort products (Hypericum perforatum) | In a study of 54 products bought in Canada and the United States, only two had a total naphthodianthrone concentration within 10% of the label claim. [12] | Published in 2003; today's products may differ |
| Ayurvedic medicines sold online | About one-fifth of the 193 products analyzed contained detectable lead, mercury or arsenic. [13] | Bought in 2005; a category of traditional medicines, not all herbal products |
Proper evidence not found: we did not find, in the sources we read, a single current measurement of how common these problems are across all herbal products on the US market. We searched PubMed for surveys of herbal supplement authenticity, metals and label accuracy. A widely discussed 2013 DNA-barcoding study of herbal products is listed on PubMed as retracted, with a retraction notice dated 2024, so we do not use its figures. [14] One review describes how adulteration for profit can occur anywhere along the supply chain, from raw botanicals to finished products. [15]
Safety: quality is not the same as safety
- Medicines. NCCIH gives St. John's wort as an example of a herb that makes many medications less effective. [1] The NHS says to check with a pharmacist before taking a herbal medicine if you already take other medicines. [4] See how interactions work.
- Hidden drugs. The FDA has found prescription drugs, including the anticoagulant warfarin and the anticonvulsant phenytoin, in products sold as dietary supplements. [1]
- Surgery, pregnancy and children. If you are having surgery, NCCIH advises telling your health care providers about all supplements you take, well ahead of the operation. [1] NCCIH notes many supplements have not been tested in pregnant women, nursing mothers or children. [1]
- Reporting. US supplement labels must give a domestic address or phone number for reporting serious adverse events. [2] See side effects and reporting.
Ask a pharmacist or clinician about any product, especially if you take prescription medicines, are pregnant or breastfeeding, have liver or kidney disease, or have surgery planned. Please do not stop or change a prescribed medicine on your own.
References
- National Center for Complementary and Integrative Health (NIH, US). Using Dietary Supplements Wisely. Page last updated January 2019. Read 2026-10-23.
- U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements. Content current as of 27 August 2026. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Herbal Medicine. Read 2026-10-23.
- National Health Service (England). Herbal medicines and complementary therapies. Page last reviewed 1 May 2026. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NIH, US). Chamomile: Usefulness and Safety. Page last updated November 2024. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NIH, US). Ginkgo: Usefulness and Safety. Page last updated February 2025. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NIH, US). Black Cohosh: Usefulness and Safety. Page last updated November 2024. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NIH, US). Milk Thistle: Usefulness and Safety. Page last updated February 2025. Read 2026-10-23.
- Fenclova M, Novakova A, Viktorova J, et al. Poor chemical and microbiological quality of the commercial milk thistle-based dietary supplements may account for their reported unsatisfactory and non-reproducible clinical outcomes. Scientific Reports. 2019;9:11118. PMID 31366891. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NIH, US). Goldenseal: Usefulness and Safety. Page last updated February 2025. Read 2026-10-23.
- Wallace ED, Oberlies NH, Cech NB, Kellogg JJ. Detection of adulteration in Hydrastis canadensis (goldenseal) dietary supplements via untargeted mass spectrometry-based metabolomics. Food and Chemical Toxicology. 2018;120:439-447. PMID 30031041. Read 2026-10-23.
- Analysis of the hypericin and pseudohypericin content of commercially available St John's Wort preparations. Canadian Journal of Clinical Pharmacology 2003;10(3):114-118. PMID 14506510. Read 2026-10-23.
- Saper RB, Phillips RS, Sehgal A, et al. Lead, mercury, and arsenic in US- and Indian-manufactured Ayurvedic medicines sold via the Internet. JAMA. 2008;300(8):915-923. PMID 18728265. Read 2026-10-23.
- Newmaster SG, et al. DNA barcoding detects contamination and substitution in North American herbal products. BMC Medicine. 2013;11:222. PubMed record marked as a retracted article, retraction notice BMC Med. 2024;22(1):279. PMID 24120035. Read 2026-10-23.
- Grazina L, Mafra I, Monaci L, Amaral JS. Mass spectrometry-based approaches to assess the botanical authenticity of dietary supplements. Comprehensive Reviews in Food Science and Food Safety. 2023;22(5):3870-3909. PMID 37548598. Read 2026-10-23.