Peptide legality in the United States: research use only, approval and compounding

"Is it legal?" has no single answer for peptides, because US law looks at a product's intended use, who makes it and how it is distributed rather than at its molecular class [1]. This guide describes the framework as it stood in October 2026. It is information only, not legal advice, and positions change; the primary sources in the reference list are the place to confirm current status.

Drug approval is the starting point

Under the Federal Food, Drug, and Cosmetic Act, nobody may introduce a new drug into interstate commerce unless an approved application is in effect for it [2]. A product is a drug when it is intended to diagnose, cure, mitigate, treat or prevent disease, or to affect the structure or any function of the body [3]. Approved peptide drugs, such as semaglutide, have FDA labels that set out indications, warnings and dosing [4]. Compounds that have never been through that process have no label, and the library marks each compound's status individually.

What "research use only" means

FDA regulation 21 CFR 312.160 contains a narrow authorization to ship a drug intended solely for tests in vitro or in animals used only for laboratory research. The package must carry the caution that it contains a new drug for investigational use only in laboratory research animals, or for tests in vitro, and is not for use in humans [5]. The shipper must use due diligence to assure that the consignee is regularly engaged in such tests, and must keep records of the recipient, date, quantity and batch for two years [5].

The label is therefore a statement about the intended customer and purpose, and it is not a legal category that makes a product acceptable for human use [5]. FDA judges intended use objectively, from labeling claims, advertising, and the circumstances of distribution [1]. In a 2024 warning letter to a chemical supplier, the agency wrote that despite statements marketing products as "research use only" and "not for human consumption," evidence from the firm's website established that they were intended as drugs for human use [6]. A June 2026 letter to another peptide seller treated website claims as evidence of intended use and described the products as unapproved new drugs [7].

Compounding under 503A and 503B

Compounded drugs are not FDA-approved, which means FDA does not verify their safety, effectiveness or quality before they are marketed [8]. Two statutory routes exist. Section 503A covers drugs compounded by a licensed pharmacist in a state-licensed pharmacy, or by a licensed physician, for an identified patient on a valid prescription [9]. Section 503B covers FDA-registered outsourcing facilities, which may not compound from a bulk drug substance unless it is on the 503B bulks list or the product is on FDA's drug shortage list [10].

Bulk substances and the interim categories

A 503A compounder may use a bulk substance only if it meets a USP or NF monograph, is a component of an FDA-approved drug, or appears on the 503A bulks list; the substance must also come with a valid certificate of analysis and be made by an FDA-registered establishment [11]. While FDA evaluates nominations, an interim policy sorts nominated substances into categories [11]. For category 1, FDA does not intend to act against compounders who meet the guidance conditions [11]. For category 2, FDA has identified significant safety risks and would consider action under its general enforcement policies [11]. Category 3 substances were nominated with insufficient information [11].

FDA's category 2 page, current as of 22 April 2026, lists GHRP-2 and GHRP-6 (503B), ipamorelin acetate (503B) and kisspeptin-10 (503A), among other substances [12]. The same page has a separate section for substances previously in category 2 and withdrawn by their nominators; it includes BPC-157, CJC-1295, epitalon, KPV, selank, semax, thymosin alpha-1, the TB-500 fragment and injectable GHK-Cu [12]. FDA's advisory committee convened on 23 and 24 July 2026 to discuss whether BPC-157, KPV, TB-500 and MOTS-c, and then emideltide, semax and epitalon, should be included on the 503A bulks list [13]. Advisory committees make non-binding recommendations, which FDA generally follows but is not legally bound to follow [13]. FDA has said that listing substances on the 503A bulks list proceeds through notice-and-comment rulemaking [11].

Why status varies and changes

Several layers move independently. Enforcement turns on intended use, so identical material can be treated differently depending on how it is described and sold [1]. Category placements change by FDA action; for example, several peptides were added to category 2 on 29 September 2023 [12]. FDA also stated that it does not intend to place substances nominated on or after 7 January 2025 into the interim categories [11]. State licensing adds another layer for pharmacies and physicians [11]. Imports face their own review: a product that requires an approved application or IND and has none is subject to refusal at entry [14]. Cosmetics, sport and shipping follow different frameworks, covered in the topical guide, the sport guide and the shipping guide; the legal status page summarizes compound-level positions.

Key points

• US law regulates by intended use, so a research-use-only label does not by itself determine legality [1, 5].
• The laboratory-research shipping provision is conditional on the recipient's genuine research purpose and on record-keeping [5].
• Compounded drugs are not FDA-approved [8].
• 503A and 503B are separate pathways with different bulk-substance rules [10, 11].
• Category placements and advisory-committee activity change over time; check FDA directly [12, 13].