Short answer
Legality depends on the product and the channel, not the molecule's name. An approved drug is legal with a prescription; the same molecule in a research-use vial is not a legal human product.
Approved drugs
FDA-approved products are legal with a prescription for their labeled uses. Prescribing them off-label is legal and common for clinicians: the evidence for the off-label use is a separate question from its legality.
Compounded drugs
Compounding pharmacies can legally prepare certain drugs for individual prescriptions under sections 503A and 503B, but compounded products are not FDA-approved and the rules around which bulk substances may be used are actively tightening: the July 2026 PCAC review covers several discussed peptides.
Investigational compounds
Compounds in clinical trials (like retatrutide) have no legal channel for general human use. Selling or marketing them for human use outside trials makes them unapproved drugs regardless of how promising the trial data looks.
Research-use-only products
A 'for research use only' label does not create legality for human use. FDA has warned repeatedly that when marketing points toward human use, RUO products are unapproved, misbranded drugs: the disclaimer does not change what the product is.
The gray market in practice
Enforcement focuses mostly on sellers rather than individual buyers, but 'rarely prosecuted' is not the same as legal. Every quality, identity, and contamination risk sits entirely with the buyer, with no regulated supply chain behind it.
Athletes: a separate prohibition
WADA rules are contractual sport rules, not laws. A peptide can be legal to purchase and still end a competitive athlete's eligibility: GH secretagogues, IGF-1 variants, and thymosin products are common examples.
Sources
- 1.
FDA. Compounding and the FDA: Questions and Answers 2026.
Accessed 2026-06-08.
FDA explains that compounded drugs are not FDA-approved and that FDA does not verify their safety, effectiveness, or quality before marketing.
- 2.
FDA. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks 2026.
Accessed 2026-06-08.
FDA summarizes potential significant safety risks and missing safety information for several nominated peptide bulk substances.
- 3.
Accessed 2026-06-08.
FDA distinguishes approved semaglutide products from compounded semaglutide products and describes dosing-error concerns.
- 4.
WADA. The 2026 Prohibited List 2026.
Accessed 2026-06-08.
WADA states that S0 non-approved substances are prohibited at all times when they have no current approval by a governmental regulatory health authority for human therapeutic use.