"For research use only" is printed on almost every peptide sold online. Many sellers regard the phrase as a legal status, as if printing it placed the product outside drug law. It does not. Under the Federal Food, Drug, and Cosmetic Act, whether a substance is a drug depends on what the seller intends it to be used for, and that intent is judged from the seller's conduct as a whole. The label is one piece of that evidence. When the rest of the evidence points the other way, the label loses.
A research-use-only label is a statement of intent. The law asks whether the rest of the business tells the same story.
A drug is defined by its intended use
The Act defines a drug largely by purpose rather than by chemistry. Section 201(g)(1) includes articles intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals
and articles (other than food) intended to affect the structure or any function of the body of man or other animals
.
The decisive word is intended. The same lyophilised peptide, from the same synthesis, can be a laboratory reagent in one seller's hands and an unapproved drug in another's. Nothing about the vial changes. What changes is the evidence of what it is for.
Objective intent
FDA's regulation on intended use, 21 CFR 201.128, makes clear that the test is not what a seller privately believes, but what its words and actions show. It was revised in a 2021 final rule, and reads in part:
The intent may be shown by such persons' expressions, the design or composition of the article, or by the circumstances surrounding the distribution of the article. This objective intent may, for example, be shown by labeling claims, advertising matter, or oral or written statements by such persons or their representatives. Objective intent may be shown, for example, by circumstances in which the article is, with the knowledge of such persons or their representatives, offered or used for a purpose for which it is neither labeled nor advertised.
Read closely, the regulation reaches well beyond the product page:
- Expressions include every statement the business makes: product descriptions, blog posts, comparison articles, emails, chat replies and social media.
- Representatives extend that to people who speak for the business, which can include staff, affiliates and promoters.
- Design or composition covers what is actually sold and how it is packaged and grouped.
- Circumstances surrounding the distribution include what the product is sold alongside, who it is sold to and how.
- Knowledge matters: an article offered or used for a purpose the seller knows about, but does not print, can still establish intent.
What a disclaimer can and cannot do
FDA's recent warning letters to peptide sellers follow a consistent pattern. Each quotes the seller's own disclaimer, and then sets it aside on the strength of everything else on the website. A letter of March 2026 is typical:
Despite statements on your product labeling marketing your products for "Research Use Only," and "not intended for human consumption, medical use, or veterinary use," evidence obtained from your website establishes that your products are intended to be drugs for human use.
A disclaimer is not ignored. It is weighed, alongside every other piece of evidence about what the product is for. A disclaimer that agrees with the rest of the business carries real weight. One that is contradicted by product descriptions, accompanying products, guides or customer communications carries very little, and the contradiction itself can become part of the case.
A disclaimer is evidence. It is not a defence.
Interpretation, not settled law. FDA's warning letters record the agency's reading of the law as applied to particular facts at a particular time. In FDA's own words, a warning letter is informal and advisory
, and the agency does not consider Warning Letters to be final agency action
. The positions described here are a guide to how FDA currently interprets the Act and its regulations, not rulings of a court, and that interpretation, the agency's enforcement priorities and the regulations themselves can change. The intended-use regulation itself has been revised and re-proposed more than once in recent years. What these letters show is how FDA weighs disclaimers today: the best available guide, not a permanent rule.
Unapproved new drugs
Once a substance is a drug, the next question is whether it is a new drug. Under section 201(p), a drug is a new drug if it is not generally recognised, among qualified experts, as safe and effective for the uses in its labeling. Section 505(a) then forbids introducing a new drug into interstate commerce without an approved application, and section 301(d) makes doing so a prohibited act.
There is no research-use exemption in section 505. The route the Act provides for using an unapproved drug in people is an investigational new drug application, under section 505(i) and 21 CFR part 312, with its own sponsor, investigator, review board and consent obligations. Research that never involves people or animals, such as biochemical and cell-based work, does not need that route, because the material is not being used as a drug.
It follows that selling a research peptide is lawful only to the extent that the business, objectively and consistently, intends it for research that does not involve its use in people.
Adequate directions for use
Section 502(f)(1) deems a drug misbranded unless its labeling bears adequate directions for use. FDA defines these, in 21 CFR 201.5, as directions under which a layman can use the drug safely and for the purposes for which it is intended. An unapproved drug intended for use in people cannot satisfy that requirement.
This produces a trap that many sellers walk into. Publishing preparation guides, calculators or amounts for use in people does not make a product compliant by adding "directions". It does the opposite: it supplies evidence of human intended use, which is what makes the product a drug in the first place.
Who is responsible
Violations of section 301 are federal crimes. Under section 303(a)(1) a first violation is a misdemeanor that does not require proof of intent to defraud. Under section 303(a)(2), a violation committed with intent to defraud or mislead, or after a prior conviction, is a felony.
Responsibility is not limited to the company. In United States v. Dotterweich (1943) and United States v. Park (1975), the Supreme Court held that corporate officers who stand in a responsible relation to a violation can be convicted without proof that they personally took part in it or knew of it. The responsibility for what a business says and sells sits, in the end, with the people who run it.
Enforcement is not theoretical. In July 2026 the operators of an online peptide business in Indiana were sentenced to 70 and 16 months in federal prison after pleading guilty to introducing unapproved new drugs into interstate commerce with intent to defraud and mislead.
Short of prosecution, FDA's tools include warning letters, which every recent letter pairs with the possibility of seizure and injunction
; import alerts, which let shipments be detained without physical examination; and public statements naming the products concerned.
Where "research use only" is actually defined
The phrase does have a defined regulatory meaning in one area: in vitro diagnostic products. There, 21 CFR 809.10(c)(2)(i) requires products in the laboratory research phase of development to carry the statement "For Research Use Only. Not for use in diagnostic procedures." FDA's 2013 guidance on that labeling is instructive beyond diagnostics: it explains that the label is not enough on its own, and that the agency looks at how a product is actually marketed and to whom.
| Setting | What the phrase does | Where the rule is |
|---|---|---|
| In vitro diagnostic products | A required labeling statement for products in the research phase; marketing for clinical diagnostic use is inconsistent with it | 21 CFR 809.10(c)(2)(i); FDA guidance, November 2013 |
| Chemicals and peptides sold for laboratory research | A statement of the seller's intended use, weighed with all other evidence of that intent | FD&C Act 201(g)(1); 21 CFR 201.128 |
| Unapproved drugs studied in people | Not applicable: such use requires an investigational new drug application | FD&C Act 505(i); 21 CFR part 312 |
What compliance actually requires
If intent is judged from everything a business says and does, then compliance cannot be achieved by a label, a checkbox or a footer. It has to be true of the whole operation: every page, every product grouping, every accompanying item, every reply to a customer, every person who speaks for the business, and every buyer it chooses to sell to. The next article in this series sets out how FDA reads that evidence in practice.
Frequently asked questions
- Does printing "not for human consumption" make a peptide legal to sell?
- No. It is a statement of intent, and FDA weighs it against all other evidence. Recent warning letters quote such statements and then find, from the rest of the website, that the products were intended for use in people.
- Can a seller be responsible for what its customers do?
- Intended use can be shown by circumstances in which a product is offered or used for a purpose the seller knows about, even if that purpose is not on the label. What a seller knows, and how it responds, is part of the evidence.
- Does describing published research count as a claim?
- It can. Recent letters quote research-framed statements, such as compounds "studied for their roles in metabolic and weight management research", as evidence of intended use, alongside more direct statements.
- Is a peptide that is also an approved medicine's active ingredient different?
- Not in the seller's favour. An approved application covers a specific product from a specific sponsor. FDA's letters note that while approved versions of a substance may exist, no approval covers the seller's product.
- Are FDA's positions in its warning letters the law?
- No. They are the agency's interpretation of the statute and its regulations as applied to particular facts. They are the best guide to how FDA is likely to act, but courts have the final word, and the agency's interpretation and priorities can change, in either direction.
- Who is liable for a violation?
- The company and, under the responsible corporate officer doctrine, the individuals in a position to prevent or correct the violation, even without proof that they personally took part.
Sources & Further Reading
- Federal Food, Drug, and Cosmetic Act §§ 201(g)(1), 201(p), 301, 303, 502(f), 505(a), 505(i); 21 U.S.C. §§ 321(g)(1), 321(p), 331, 333, 352(f), 355(a), 355(i).
- 21 CFR 201.5, Drugs; adequate directions for use.
- 21 CFR 201.128, Meaning of "intended uses".
- Food and Drug Administration. Regulations regarding "intended uses". Final rule. Federal Register 2021;86:41383. August 2, 2021.
- 21 CFR 809.10(c), Labeling for in vitro diagnostic products.
- Food and Drug Administration. Distribution of In Vitro Diagnostic Products Labeled for Research Use Only or Investigational Use Only. Guidance for industry and FDA staff. November 2013.
- 21 CFR part 312, Investigational new drug application.
- United States v. Dotterweich, 320 U.S. 277 (1943).
- United States v. Park, 421 U.S. 658 (1975).
- Food and Drug Administration, Center for Drug Evaluation and Research. Warning letter to Gram Peptides, reference 721806. March 31, 2026.
- Food and Drug Administration, Center for Drug Evaluation and Research. Warning letter to Royal Peptides LLC, reference 734884. August 24, 2026.
- Food and Drug Administration. Warning letter to USApeptide.com, reference 696885. February 26, 2025.
- United States Attorney's Office, Northern District of Indiana. United States v. Matthew Kawa; sentencing of July 30, 2026.
- Food and Drug Administration. Regulatory Procedures Manual, Chapter 4: Advisory Actions (Warning Letters and Untitled Letters).
See also
- How the FDA decides what a product is for
- Common mistakes in research-use-only supply
- What strict compliance costs
- Where research-use-only regulation is heading
- Intended use — glossary
- Unapproved new drug — glossary
- Adequate directions for use — glossary
- Responsible corporate officer doctrine — glossary
- Research use only — glossary
For in vitro laboratory research only. Not for human or veterinary use. This library describes chemistry, analytical methods and published laboratory research; it gives no guidance on use in people or animals.