What Are Peptides?

Peptides are short chains of amino acids — typically 2 to 50 residues — linked by peptide bonds. They sit between single amino acids and full proteins in size. Many hormones, signalling molecules, and natural regulators in the human body are peptides: insulin, oxytocin, and growth hormone–releasing hormone are all examples.

In a research context, peptides are studied for their potential effects on tissue repair, metabolism, inflammation, cognition, body composition, and more. Some peptides are well-characterised in clinical literature; others have only preclinical (animal or in vitro) data behind them.

What This Knowledge Base Covers

Peptide Data is a UK-focused research and educational resource. Every compound profile in this knowledge base includes:

  • Mechanism of action — how the peptide is understood to work at a molecular level
  • Research summary — what the published evidence says, graded by quality
  • Commonly discussed protocols — dosing patterns reported in research literature (not medical advice)
  • Storage and reconstitution — practical handling information
  • Blood work — relevant biomarkers to monitor in research settings
  • UK legal status — how the peptide is classified under UK law
  • Vetted UK vendors — suppliers that meet our verification criteria
  • References — peer-reviewed citations for every factual claim

Key Terms to Know

Reconstitution — Peptides are typically supplied as lyophilised (freeze-dried) powder and must be dissolved in a solvent such as bacteriostatic water before use in research.

Purity — The percentage of the sample that is the stated peptide, verified by analytical testing (HPLC). Reputable vendors provide a Certificate of Analysis (CoA).

Research use only — Peptides sold by research suppliers are not licensed medicines. They are intended for in vitro research, laboratory study, or animal models — not human consumption.

Growth hormone secretagogues (GHS) — A class of peptides that stimulate growth hormone release (e.g., ipamorelin, CJC-1295, GHRP-6).

GLP-1 receptor agonists — A class of metabolic peptides used in diabetes and obesity research (e.g., semaglutide, tirzepatide, retatrutide).

Understanding Evidence Grading

Each compound profile in this knowledge base includes an evidence grade:

  • Strong evidence — Multiple large, randomised controlled trials in humans, published in peer-reviewed journals.
  • Moderate evidence — Some human clinical data, smaller trials, or robust preclinical evidence.
  • Limited evidence — Primarily animal or in vitro studies; few or no human trials.
  • Anecdotal only — Reports from user communities or practitioner experience, without peer-reviewed backing.

This grading helps you weigh how much confidence to place in the findings. Many popular research peptides fall into the "limited evidence" category — the animal data may be promising, but human clinical confirmation is lacking.

UK Legal Status: The Basics

In the United Kingdom, research peptides are not controlled substances in the way that recreational drugs are. However, their legal status varies:

  • Legal for research purposes — Many peptides can be sold and purchased for legitimate research use. They are not licensed as medicines by the MHRA (Medicines and Healthcare products Regulatory Agency).
  • Prescription-only medicines (POM) — Some peptides (e.g., semaglutide, liraglutide) are licensed medicines in the UK and are legally available only by prescription. Supplying these without a prescription is illegal.
  • Grey area — Some compounds sit in a regulatory grey zone where their status depends on intended use and how they are marketed.

For a detailed breakdown, read our UK Legal Status of Research Peptides guide.

Choosing a Vendor

Not all peptide vendors are equal. When evaluating a supplier, look for:

  1. Certificate of Analysis (CoA) — Third-party testing confirming purity and identity.
  2. Transparency — Clear product information, batch numbers, and contact details.
  3. Reputation — Independent reviews on forums such as r/Peptides, r/PeptidesUK, and r/biohacking.
  4. Shipping and storage — Proper packaging and cold-chain shipping where required.

See our Vendor Vetting Guide for a full framework, and our individual vendor profiles for assessed UK suppliers.

Where to Go Next

Browse our compound profiles for detailed information on specific peptides, or check our news articles for the latest research developments.

Important Disclaimer

All content on Peptide Data is for research and educational purposes only. Nothing on this site constitutes medical advice. Peptides discussed here are not licensed medicines and are not approved for human consumption unless stated otherwise. Always consult a qualified healthcare professional before making any health-related decisions.