Answers to the most frequently asked questions about peptides, from basic science to regulatory status and safety.
Filed under basics, written for beginner, patient-consumer, journalist.
Not medically reviewed. Last updated 2026-05-01. Nothing here is medical advice.
This FAQ addresses the most common questions we receive about peptides, organized by topic.
**Q: What is the difference between a peptide and a protein?**
A: Both are chains of amino acids. Peptides are generally 2-50 amino acids, while proteins are longer (50+). The distinction is somewhat arbitrary — insulin (51 amino acids) is sometimes classified as either.
**Q: Are all peptides drugs?**
A: No. Peptides exist naturally in food, in the body, and in cosmetic products. A peptide becomes a "drug" when it is intended to treat, cure, prevent, or mitigate disease.
**Q: Are peptides safe?**
A: Approved peptide medications have been extensively tested for safety. Unauthorized peptide products have not been tested and may carry significant risks.
**Q: Are peptides legal?**
A: Approved peptide medications are legal with a prescription. Unauthorized peptide products may be illegal to sell for human use. "Research use only" labeling does not make a product legal for human consumption.
**Q: Can my doctor prescribe compounded peptides?**
A: In the United States, licensed physicians can prescribe compounded medications from licensed pharmacies. However, compounded drugs are not FDA-approved and have not undergone the same testing as approved medications.
**Q: Are peptides banned in sports?**
A: Many peptides are prohibited by WADA, including growth hormone-releasing peptides, EPO analogs, and IGF-1. Athletes should check the WADA Prohibited List before using any substance.
**Q: How do I know if a peptide product is safe?**
A: FDA-approved peptide medications from licensed pharmacies are the safest option. Products sold online as "research use only" have not been tested for safety in humans.
**Q: What are the risks of unauthorized peptide products?**
A: Risks include contamination, incorrect dosing, wrong substance, infection (for injectables), and unknown long-term side effects.
**Q: How do I know if a peptide claim is supported by evidence?**
A: Check PubMed for peer-reviewed studies, ClinicalTrials.gov for human trial data, and regulatory databases for approval status. See our Evidence Ratings guide for a framework.
This FAQ is for educational purposes only.
More guides: All guides, Safety centre, Peptide library.