What Are Peptides? Definition, Examples, and Which Are FDA-Approved
Peptides are short chains of amino acids, typically 2 to 50, linked by peptide bonds. Longer chains are polypeptides and proteins. Some peptides are FDA-approved medicines, including semaglutide (Ozempic, Wegovy) and tirzepatide (Zepbound). Many peptides sold online for research, such as BPC-157 and TB-500, are not FDA-approved medicines.[1][3][7]
What is a peptide?
The National Human Genome Research Institute defines a peptide as a short chain of amino acids, typically 2 to 50, linked by chemical bonds called peptide bonds. A longer chain of 51 or more is called a polypeptide.[1] An amino acid is a single building block, a peptide bond is the link between two of them, and a chain is a peptide. Some medicines are built this way. The Ozempic label describes semaglutide as a human GLP-1 receptor agonist, or GLP-1 analog, with a peptide backbone produced by yeast fermentation.[3] The Zepbound label describes tirzepatide as a GIP receptor and GLP-1 receptor agonist.[4] The Egrifta WR label describes tesamorelin as a growth hormone-releasing factor analog made of a 44 amino acid sequence.[5] Being a peptide says nothing about whether a product is safe, approved, or right for a person. The product label and a prescriber answer those questions.
- Amino acid
- A single building block that is linked into chains.[1]
- Peptide
- A short chain of amino acids, typically 2 to 50, linked by peptide bonds.[1]
- Peptide bond
- The chemical bond that links one amino acid to the next.[1]
- Polypeptide
- A longer chain of linked amino acids, 51 or more by the NHGRI count.[1]
- Protein
- Built from one or more polypeptides. The FDA treats a defined-sequence chain of more than 40 amino acids as a protein.[2]
- GLP-1 receptor agonist
- A medicine that activates the receptor for glucagon-like peptide-1, such as semaglutide.[3]
- Lyophilized
- Freeze-dried into a powder, so a liquid must be added before use. See how to reconstitute peptides.
- Half-life
- The time for the amount of a drug in the body to fall by half. The Ozempic label gives about 1 week for semaglutide.[3]
What is the difference between a peptide and a protein?
The difference is mostly size, and two official definitions draw the line in different places. The NHGRI says a peptide is typically 2 to 50 amino acids, a chain of 51 or more is a polypeptide, and proteins are built from one or more polypeptides.[1] The FDA, in a 2020 final rule, defined the term protein as any alpha amino acid polymer with a specific, defined sequence that is greater than 40 amino acids in size.[2] So a chain with 44 amino acids is a peptide by the NHGRI range and sits above the FDA line. Tesamorelin has 44 amino acids according to its label.[5] That is why the word on its own does not settle how a product is classified or regulated. The product label, not the vocabulary, tells you what you have. Structure also matters, since proteins fold into shapes, but length is the practical yardstick.
| Feature | Amino acid | Peptide | Protein |
|---|---|---|---|
| What it is | A single building block | A short chain of amino acids joined by peptide bonds | One or more polypeptide chains |
| Size by NHGRI | 1 | Typically 2 to 50[1] | Built from polypeptides of 51 or more[1] |
| Size by FDA rule | Not applicable | Not above 40, by the same line[2] | More than 40, with a defined sequence[2] |
| Example on this page | Not covered | Tesamorelin has 44 amino acids, between the two lines[5] | Not covered |
Which peptides are FDA-approved medicines?
Several, and each is approved for a specific use on its own label. The Ozempic label says it is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes.[3] Zepbound is the tirzepatide product, and Wegovy is another semaglutide product that also comes as a tablet taken by mouth once daily.[4][6] Egrifta WR is indicated for the reduction of excess abdominal fat in HIV-infected adult patients with lipodystrophy.[5] Insulin is an older example of a hormone medicine. The FDA's history of insulin dates its first clinical success to January 1922.[10] Approval always covers a named product, dose form, and use. It does not extend to every product that shares a molecule name. Read the indication on the label itself instead of relying on a summary, including this one, and let your prescriber decide what applies to you.
| Peptide | FDA status on the date above | Source |
|---|---|---|
| Semaglutide | Approved in Ozempic and Wegovy, which are prescription products | Product labels[3][6] |
| Tirzepatide | Approved in Zepbound, a prescription product | Product label[4] |
| Tesamorelin | Approved in Egrifta WR, a prescription product | Product label[5] |
| Retatrutide | The FDA says it cannot be used in compounding under federal law | FDA alert[8] |
| BPC-157 | Not an FDA-approved medicine; listed by the FDA among compounding substances with safety concerns | FDA compounding page[7] |
| TB-500 | Not an FDA-approved medicine; listed by the FDA as nominated but withdrawn for compounding | FDA compounding page[7] |
Are research peptides like BPC-157 and TB-500 FDA-approved?
No. Neither has an FDA label as a medicine. The FDA's compounding safety page states that compounded drugs containing BPC-157 may pose a risk for immunogenicity for certain routes of administration and may have complexities with peptide-related impurities and active pharmaceutical ingredient characterization.[7] On the page version we read, dated April 22, 2026, BPC-157 and TB-500 sit in a group labeled nominated but withdrawn, which means they are not currently under review for the compounding bulk lists.[7] An FDA advisory committee met on July 23 and 24, 2026 to discuss whether BPC-157, TB-500, and other substances should be added to the 503A bulks list. The FDA says advisory committees make non-binding recommendations.[9] A committee recommendation is not FDA approval and does not by itself change the list. Status moves, so re-check the FDA pages. PepTrac does not recommend any compound.
Are peptides legal?
This page cannot give legal advice, but the FDA's public position is clear on several points. Approved peptide drugs such as Ozempic, Wegovy, and Zepbound are prescription products.[3][6][4] The FDA says compounded drugs are not FDA-approved, which means the agency does not review them for safety, effectiveness, or quality.[8] The agency also warns about companies illegally marketing unapproved drugs that are falsely labeled for research purposes or not for human consumption while giving dosing instructions for human use.[8] For retatrutide, the FDA says it cannot be used in compounding under federal law.[8] The FDA also describes dosing errors with compounded products, some needing hospital care.[8] A product described as for research use only is not a prescription medicine with a label, and no label means no approved dose, site, or storage instructions. Speak to a licensed prescriber and pharmacist about what applies to you.
Are peptides banned in sports?
Some are. The United States Anti-Doping Agency states that BPC-157 is prohibited under the S0 Non-Approved Substances category of the World Anti-Doping Agency's Prohibited List.[11] Other peptides may be listed in other categories, so no single sentence covers every compound. Product labels cannot settle the question for an athlete either. The FDA says compounded drugs are not reviewed for safety, effectiveness, or quality, and it warns about products falsely labeled for research purposes, so a label alone is not proof of what a vial contains.[8] This page did not verify the status of each peptide in the table above against the current List, so it makes no claim about them. Athletes should check the current Prohibited List and ask their national anti-doping organization before using any peptide or supplement, and should not rely on an online article, including this one, for a clearance.
How do people take peptides?
The route depends on the product, and the label states it. Ozempic and Zepbound are given as subcutaneous injections, which means under the skin of the abdomen, thigh, or upper arm, with the exact sites listed on each label.[3][4] Wegovy comes as an injection and also as a tablet that the label says to take once daily on an empty stomach in the morning with water.[6] Egrifta WR is a powder mixed with a diluent and injected into the abdomen.[5] That variety is why no single how-to covers all peptides. The injection sites guide compares what the labels say, and the reconstitution guide explains the math for a dry vial. Neither one gives a dose. Dose, timing, and route are decisions for you and your prescriber, based on the label for the exact product you hold.
Frequently asked questions
Is semaglutide a peptide?
Yes. The Ozempic label describes semaglutide as a human GLP-1 receptor agonist, or GLP-1 analog, with a peptide backbone. It is an FDA-approved ingredient in prescription products.
Are collagen peptides the same thing?
Not as injectable drugs. Collagen peptides are food-derived peptide fragments sold as supplements. This page makes no benefit claims about them and only notes that the word peptide covers different products.
Is BPC-157 FDA-approved?
No. It is not an FDA-approved medicine. The FDA's compounding safety page raises concerns about immunogenicity and peptide-related impurities in compounded products that contain it.
Are peptides steroids?
No. Peptides are chains of amino acids joined by peptide bonds. This page does not cover how anti-doping bodies group substances, so check the current Prohibited List if you compete in sport.
Do I need a prescription for peptides?
Approved peptide drugs such as Ozempic, Wegovy, Zepbound, and Egrifta WR are prescription products. Ask a prescriber and a pharmacist about your situation. This page is not legal or medical advice.
Does PepTrac sell or recommend peptides?
No. PepTrac is an iPhone record-keeping app, free to download with an optional PepTrac Pro subscription, published by Blanket LLC. It does not sell peptides or tell you what to take.
Sources
- National Human Genome Research Institute. Talking Glossary of Genomic and Genetic Terms: Peptide. Accessed October 3, 2026.
- Federal Register (U.S. Food and Drug Administration). Definition of the Term Biological Product (final rule, February 21, 2020). Accessed October 3, 2026.
- DailyMed, National Library of Medicine (Novo Nordisk). Ozempic (semaglutide) injection prescribing information. Accessed October 3, 2026.
- DailyMed, National Library of Medicine (Eli Lilly). Zepbound (tirzepatide) prescribing information. Accessed October 3, 2026.
- DailyMed, National Library of Medicine (Theratechnologies). Egrifta WR (tesamorelin) prescribing information. Accessed October 3, 2026.
- DailyMed, National Library of Medicine (Novo Nordisk). Wegovy (semaglutide) prescribing information. Accessed October 3, 2026.
- U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Accessed October 3, 2026.
- U.S. Food and Drug Administration. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. Accessed October 3, 2026.
- U.S. Food and Drug Administration. July 23-24, 2026 Meeting of the Pharmacy Compounding Advisory Committee. Accessed October 3, 2026.
- U.S. Food and Drug Administration. 100 Years of Insulin. Accessed October 3, 2026.
- U.S. Anti-Doping Agency. Is BPC-157 prohibited?. Accessed October 3, 2026.
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