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Glossary

What is supplement potency testing?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

A potency test measures how much of an ingredient a product actually contains, for comparison with the amount on its label. FDA's manufacturing rule calls this strength and requires a strength specification for every finished batch (21 CFR 111.70). Results are often reported as a percentage of the declared amount.1,2

Key facts

  • FDA does not test supplements before they are sold. Under the manufacturing rule, measuring strength is the maker's job.1,3
  • An FDA survey of 110 melatonin products marketed for children found 0% to 667% of the declared melatonin.2
  • In 11 coenzyme Q10 products, total CoQ10 measured 82% to 166% of the declared amount.4
  • High potency has a legal meaning on a label: a vitamin or mineral at 100% or more of its Reference Daily Intake.5
  • In 2005 FDA warned a firm whose products were significantly subpotent in vitamin A, folic acid and vitamin C.6

Potency, strength and the label

FDA's rule uses the word strength, one of four qualities a maker must specify for every finished batch along with identity, purity and composition. A potency result answers the strength question: how much is there?1

The answer is set against the amount the Supplement Facts panel declares per serving. A result of 100% means the measured amount equals the declared amount.2

Makers choose which specifications to test on a statistically sampled subset of finished batches, or on every batch, so that the results show all specifications are met.7

How potency is measured

Label accuracy studies often use liquid chromatography, which separates a sample's compounds so each can be measured. The FDA melatonin survey paired it with mass spectrometry, and the CoQ10 study with ultraviolet detection.2,4

Botanical extracts are harder. Their strength is often expressed as a marker compound, such as the flavonol glycosides in ginkgo extract, and a marker can be faked. Researchers found ginkgo extracts commonly spiked with pure flavonoids or cheaper flavonoid rich extracts.8

Probiotics are counted rather than weighed. Their potency is the number of live organisms of the labeled strains, which can fall during storage.9,10

When results miss the label

FDA's 2007 rule followed recalls of products that held more or less of an ingredient than the label claimed, or none at all. FDA also cited private laboratory analyses that found many products did not contain the amounts on their labels.6

Too much can matter as much as too little. FDA noted that a vitamin such as vitamin D at many times the intended level can lead to illness and hospitalization.11

How far a result may sit from the label before a product is out of compliance is covered under label claim. Why many products test above 100% is covered under overage.12,13

Questions people ask

What does high potency mean in supplements?

It is a defined claim. A single vitamin or mineral can be called high potency at 100% or more of its Reference Daily Intake. A multivitamin can use the term when at least two thirds of the vitamins and minerals it contains at 2% or more of the Reference Daily Intake are present at 100% or more.5

Does a potency test show that a supplement works?

No. It measures how much of an ingredient is present, not what it does in the body. NCCIH also notes that products sold in stores may differ in important ways from the products used in studies.14

Why would a product test above 100% of its label?

Makers often add extra of ingredients that break down over time, so the product still meets its label late in its shelf life. This extra is called an overage.11,13

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Sources

  1. 21 CFR 111.70. What specifications must you establish? Opened 2026-10-07.
  2. Pawar RS, Coppin JP, Khanna S, Parker CH. A survey of melatonin in dietary supplement products sold in the United States. Drug Test Anal. 2025;17(8):1176-1185. Opened 2026-10-07.
  3. U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements. Content current as of August 27, 2026. Opened 2026-10-07.
  4. Temova Rakuša Ž, Kristl A, Roškar R. Stability of reduced and oxidized coenzyme Q10 in finished products. Antioxidants (Basel). 2021;10(3):360. Opened 2026-10-07.
  5. 21 CFR 101.54(f). Nutrient content claims: high potency. Opened 2026-10-07.
  6. U.S. Food and Drug Administration. Backgrounder on the Final Rule for Current Good Manufacturing Practices (CGMPs) for Dietary Supplements. June 22, 2007. Opened 2026-10-07.
  7. 21 CFR 111.75. What must you do to determine whether specifications are met? Opened 2026-10-07.
  8. Avula B, Sagi S, Gafner S, et al. Identification of Ginkgo biloba supplements adulteration using high performance thin layer chromatography and ultra high performance liquid chromatography-diode array detector-quadrupole time of flight-mass spectrometry. Anal Bioanal Chem. 2015;407(25):7733-7746. Opened 2026-10-07.
  9. Zawistowska-Rojek A, Zaręba T, Tyski S. Microbiological testing of probiotic preparations. Int J Environ Res Public Health. 2022;19(9):5701. Opened 2026-10-07.
  10. Brousilova T, Vlkova E, Neuzil-Bunesova V, Musilova S, Kadlec-Modrackova N. Storage temperature as a determinant of probiotic long-term stability in commercial dietary supplements. Front Nutr. 2026;13:1933900. Opened 2026-10-07.
  11. Food and Drug Administration. Current Good Manufacturing Practice in Manufacturing, Packaging, Labeling, or Holding Operations for Dietary Supplements; Final Rule. Federal Register 72 FR 34752, June 25, 2007. Opened 2026-10-07.
  12. 21 CFR 101.9(g). Nutrition labeling of food: how compliance is determined. Opened 2026-10-07.
  13. Andrews KW, Roseland JM, Gusev PA, et al. Analytical ingredient content and variability of adult multivitamin/mineral products: national estimates for the Dietary Supplement Ingredient Database. Am J Clin Nutr. 2017;105(2):526-539. Opened 2026-10-07.
  14. National Center for Complementary and Integrative Health. Using Dietary Supplements Wisely. Last updated January 2019. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.