What are peptides, what is peptide therapy, and are peptides legal?

What is a peptide?

A peptide is a short chain of amino acids, the same building blocks that make up proteins. FDA regulations define a protein as an amino acid chain of more than 40 amino acids, so shorter chains are generally called peptides. 21 CFR 600.3

A protein is, under FDA regulations, any alpha amino acid polymer with a specific, defined sequence that is greater than 40 amino acids in size. 21 CFR 600.3

Insulin, first made as a therapy in 1921, is described as the first therapeutic peptide. Therapeutic peptides

Since March 23, 2020, insulin products have been regulated in the US as biological products rather than as drugs. FDA (Feb 2020)

Which peptides are FDA-approved drugs?

Several well-known medicines are peptides. On DiscoverMedica, semaglutide (Wegovy, Ozempic), tirzepatide (Zepbound, Mounjaro), liraglutide (Saxenda, Victoza) and tesamorelin (Egrifta) are FDA-approved peptide drugs with official prescribing information. Worldwide, more than 80 peptide drugs have been approved. Therapeutic peptides

• Semaglutide: approved for weight management, heart risk reduction and type 2 diabetes. Wegovy label
• Tirzepatide: approved for weight management, obstructive sleep apnea with obesity and type 2 diabetes. Zepbound label
• Liraglutide: approved for weight management and type 2 diabetes, with generics available. Saxenda label
• Tesamorelin: approved to reduce excess abdominal fat in adults with HIV-associated lipodystrophy. Egrifta label

What is the difference between an approved peptide, a compounded peptide and a research peptide?

An approved peptide has passed FDA review for a specific use. A compounded peptide is prepared by a licensed pharmacy for an individual prescription, using an ingredient FDA allows for compounding, and is not FDA-approved. A research peptide is sold as a laboratory chemical, is not for human use, and has no lawful route to you. FDA

Products sold as research chemicals carry labels such as “not for human or veterinary use,” and FDA treats them as unapproved drugs when they are marketed for people. FDA warning letter

Are peptides in skin care the same as peptide injections?

No. Topical peptides such as GHK-Cu, a copper peptide, are sold legally as cosmetic ingredients. Injectable GHK-Cu is a separate, unapproved use; non-injectable GHK-Cu is in FDA’s 503A Category 1, with an advisory committee review planned. FDA

What is peptide therapy?

“Peptide therapy” is a marketing term, not a defined treatment. Clinics use it for injected peptides such as BPC-157, TB-500, CJC-1295 with ipamorelin, tesamorelin and GHK-Cu. A 2026 review for sports medicine physicians found the evidence for these uses is largely preclinical, and said their indications, frequency and duration of use remain unknown. Injectable peptide therapy

The same review notes that tesamorelin is approved only for HIV-associated lipodystrophy, with no supporting orthopaedic evidence, and that BPC-157 findings are largely unvalidated in human trials. Injectable peptide therapy

Where a clinic offers a peptide, the lawful versions are an FDA-approved drug used on or off label, or a compounded product made by a licensed pharmacy from an ingredient FDA allows for compounding. Compounded drugs are not FDA-approved. FDA

• Ask whether the peptide is an FDA-approved drug, a compounded product, or neither.
• Ask which licensed pharmacy prepares it, and whether that pharmacy is a 503A pharmacy or a 503B outsourcing facility. FDA
• Ask what human evidence supports the use you are being offered, and what is known about its risks.

Are peptides legal in the US?

It depends on the peptide and the route. An FDA-approved peptide drug is legal with a prescription. A compounded peptide is lawful only when a licensed pharmacy makes it for an individual prescription from an eligible ingredient. Cosmetic peptides in skin care need no FDA approval. Peptides sold “for research use only” are not lawful for human use. FDA

FDA treats a product marketed for people as a drug whatever its label says, and has sent warning letters to sellers of peptides labeled “for research use only.” FDA warning letter

Sport has its own rules: the World Anti-Doping Agency prohibits many peptides at all times, BPC-157 among them, even where no criminal law applies. USADA

For the details on a single peptide, see the BPC-157 legal status guide and the guide to what “research use only” means, both linked below.

How can you tell which kind of peptide you are looking at?

Check its regulatory status, not the marketing. An FDA-approved peptide has prescribing information on DailyMed and is dispensed by a pharmacy on a prescription. A research peptide has neither. Every compound page on DiscoverMedica states its status first. Wegovy label

• Search the name on DailyMed. Approved drugs have official labels there.
• Ask who prescribes it and which licensed pharmacy fills it.
• Treat “research use only” or “not for human consumption” as a stop sign for anything meant for your body. FDA warning letter

What are peptides: questions, answered

Sources

1. 21 CFR 600.3: Biological products, definitions (Cornell LII)
2. FDA (Feb 2020): Regulatory transition of insulin and other biological products
3. Therapeutic peptides: current applications and future directions (Signal Transduct Target Ther 2022)
4. DailyMed: Wegovy (semaglutide) prescribing information, revised June 2026
5. DailyMed: Zepbound prescribing information
6. DailyMed: Saxenda (liraglutide) prescribing information
7. DailyMed: Egrifta (tesamorelin) prescribing information
8. FDA: Compounding and the FDA, questions and answers
9. FDA: 503A bulk drug substance categories list (May 14, 2026)
10. FDA warning letter: Peptide Partners (Aug 24, 2026)
11. Injectable peptide therapy: a primer for orthopaedic and sports medicine physicians (Am J Sports Med 2026)
12. FDA: Is it really “FDA approved”? (updated May 4, 2026)
13. FDA: Information for outsourcing facilities (503B)
14. USADA: BPC-157, prohibited peptide

Last reviewed October 7, 2026. Every source above was checked on or before that date. Educational information only, not medical advice; it does not replace a conversation with a licensed clinician. DiscoverMedica does not employ clinicians.