The practical answer
Most of these labels describe a regulatory pathway or intended use, not product quality. RUO and IUO are US labelling statements defined for in vitro diagnostic products; GMP covers how drugs are manufactured; GLP covers nonclinical safety studies; an API is a substance intended for a finished drug; an NDC is an FDA product identifier. FDA says an NDC does not denote approval, and that registration or listing does not denote approval either. [1] [4] [7] [8]
Evidence, method & source dates ↓How to read regulatory labels on a listing
Peptide listings borrow regulatory vocabulary freely. The words have precise legal meanings, usually narrower than the listing implies. Each entry below gives the legal source and what the label does not tell you.
Under FDA's approach, what a product is depends on its intended use, judged from the totality of circumstances, not on a label alone. FDA's 2013 guidance on research-use and investigational-use diagnostic products says statements in labelling, advertising and promotion, the product's design and how it is sold can show an intended use that conflicts with an RUO label. [2]
Research and investigational labels
These labels describe where a product sits in research or clinical development. All of them come from the in vitro diagnostic and investigational drug rules, not from any rule written for research chemicals.
| Term | Meaning and source | What it does not mean |
|---|---|---|
| RUO, research use only | For in vitro diagnostic products, the required statement is 'For Research Use Only. Not for use in diagnostic procedures.' [1] FDA describes an RUO diagnostic product as one in the laboratory research phase of development. [2] | It is not a regulatory category for peptides sold as chemicals, and it does not override other evidence of intended use [2] |
| IUO, investigational use only | For in vitro diagnostic products being tested, the statement is 'For Investigational Use Only. The performance characteristics of this product have not been established.' [1] | Not a label for research chemicals; it applies to diagnostic devices under investigation |
| Investigational new drug | A new drug or biological drug used in a clinical investigation. [3] | Not a description of a catalogue peptide; it refers to a drug in a clinical study |
| IND | An investigational new drug application, the notice of claimed exemption for a new drug. [3] | An application filed with FDA for a clinical investigation, not a product label or a quality grade |
| Clinical investigation | Any experiment in which a drug is administered or dispensed to, or used involving, one or more human subjects. [3] | Laboratory research is not a clinical investigation |
Quality-system labels
These labels describe how something was made, tested or registered. None of them is a quality grade that a seller can award itself.
| Term | Meaning and source | What it does not mean |
|---|---|---|
| CGMP, current good manufacturing practice | FDA's minimum requirements for the methods, facilities and controls used to make drugs, which assure identity, strength, quality and purity. Drugs not made under CGMP are adulterated, which describes how they were made, not necessarily that something is wrong with them. [4] | 'GMP-grade' on a listing is a claim, not an FDA certification; FDA does not approve facilities on their own [8] |
| GLP, good laboratory practice | 21 CFR Part 58 rules for nonclinical laboratory studies that support or are intended to support FDA research or marketing applications. [5] | Not a grade of material; a GLP study needs the test article characterized by the study, not just a supplier claim |
| FDA registered | Establishments that make or relabel drugs register and list with FDA. [6] | FDA says mere registration of an establishment or listing of a drug does not denote approval [8] |
| FDA approved | New drugs and biological products generally need approval before marketing. [8] | Compounded drugs are not FDA approved, and approval attaches to a product, not to a supplier [8] |
Product identity labels
These terms classify what a substance is for. US terms come from FDA registration and biologics rules; the EU terms come from the medicines directive.
| Term | Meaning and source | What it does not mean |
|---|---|---|
| API, active pharmaceutical ingredient | Any substance intended for incorporation into a finished drug product. [6] | Calling a powder an API does not make it one made under drug CGMP |
| Bulk drug substance | Has the same meaning as API for the compounding provisions of sections 503A and 503B. [6] | Not a statement that a substance may be used in compounding |
| Finished drug product | A finished dosage form, such as a tablet, capsule or solution, containing at least one API. [6] | |
| NDC, National Drug Code | A unique three-segment number used as FDA's identifier for drugs. [7] | FDA says assigning an NDC does not in any way denote FDA approval, and that inclusion in the directory does not mean FDA verified the information [7] |
| Protein (US biologics law) | Any alpha amino acid polymer with a specific, defined sequence that is greater than 40 amino acids in size. [9] | The definition does not by itself say how a polymer of 40 or fewer amino acids is classified |
| Medicinal product (EU) | A substance presented as treating or preventing disease in humans, or one that may be used in or administered to humans to restore, correct or modify physiological functions or make a diagnosis. [10] | A research-only statement does not decide the question if the product is presented or used that way |
| Active substance (EU) | A substance intended to be used in manufacturing a medicinal product and to become its active ingredient. [10] |
Common misreadings
Listings and sales pages often stack these terms to signal quality. Read each one against its definition.
- 'RUO' plus a use claim: FDA treats promotion and how a product is sold as evidence of intended use, so the label does not neutralise the claim. [2]
- 'Made in an FDA-registered facility': registration does not denote approval of the facility or the product. [8]
- 'Has an NDC': an NDC does not denote approval. [7]
- 'GMP-grade': ask which GMP standard, which site, and for evidence, such as an inspection history; a word on a label is not evidence.
- 'GLP-tested': GLP governs studies, not products; ask which study and which facility.
- 'Pharmaceutical-grade API': under 21 CFR 207.1 an API is defined by intended incorporation into a finished drug product, not by purity. [6]
Where to go deeper
Several existing guides on this site expand individual entries: what FDA warning letters say about research-use-only labels, how to check whether a peptide is FDA approved, the difference between research grade and GMP grade, the rules for research peptides in the UK and the EU, and how 503A compounding categories work. Each uses its own dated sources; check them before relying on a label in a purchasing decision.
Questions before you decide
Does 'research use only' have a legal definition for peptides?
The statement is defined in 21 CFR 809.10 for in vitro diagnostic products. FDA's guidance says intended use is judged from all the circumstances, so the label alone does not decide how a product is regulated.
Does an NDC number mean a product is FDA approved?
No. FDA's NDC Directory page says assigning an NDC does not in any way denote FDA approval, and inclusion in the directory does not mean FDA verified the information.
Is 'FDA registered' the same as 'FDA approved'?
No. FDA says mere registration of an establishment or listing of a drug does not denote approval, and the agency does not approve manufacturing facilities on their own.
What is the difference between GMP and GLP?
CGMP sets minimum requirements for how drugs are manufactured. GLP, under 21 CFR Part 58, governs nonclinical laboratory studies supporting FDA applications. Neither is a grade printed on a powder.
Check the underlying evidence
Sources & review dates
- 21 CFR 809.10 Labeling for in vitro diagnostic products (Cornell LII) ↗Accessed 30 Oct 2026
- FDA guidance: Distribution of In Vitro Diagnostic Products Labeled for Research Use Only or Investigational Use Only (November 2013) ↗Accessed 30 Oct 2026
- 21 CFR 312.3 Definitions and interpretations, investigational new drug application (Cornell LII) ↗Accessed 30 Oct 2026
- FDA: Facts About the Current Good Manufacturing Practice (CGMP) ↗Accessed 30 Oct 2026
- 21 CFR 58.1 Scope (Cornell LII) ↗Accessed 30 Oct 2026
- 21 CFR 207.1 Definitions for drug establishment registration and listing (Cornell LII) ↗Accessed 30 Oct 2026
- FDA: National Drug Code Directory ↗Accessed 30 Oct 2026
- FDA consumer update: Is It Really 'FDA Approved'? ↗Accessed 30 Oct 2026
- FDA: Definition of the Term 'Biological Product', final regulatory impact analysis ↗Accessed 30 Oct 2026
- Directive 2001/83/EC Article 1 definitions (legislation.gov.uk) ↗Accessed 30 Oct 2026
Sources are documentary evidence. They do not establish firsthand testing of a listed supplier.