The distinction is a rough convention, not a hard scientific line: shorter amino-acid chains are usually called peptides, longer ones that often fold into complex 3D shapes are called proteins. Insulin, for example, is sometimes described as one of the largest peptides or one of the smallest proteins, depending on which textbook you read — the boundary is fuzzy by design.
The word "peptide" alone tells you nothing about legal or regulatory status. Some peptides are approved medications — insulin and the GLP-1 class of drugs (semaglutide, tirzepatide) are peptides that went through full drug approval. Others are sold as research chemicals, labelled "for research use only," without that approval process. The difference is in the specific compound and how it's sold, not in the category "peptide" itself.
| Category | What it generally refers to |
|---|---|
| Metabolic/GLP-1 class | Compounds like semaglutide, tirzepatide, retatrutide |
| Growth hormone secretagogues | Compounds like CJC-1295, ipamorelin, sermorelin |
| Tissue-focused research peptides | Compounds like BPC-157, TB-500 |
| Bioregulators / signaling peptides | Compounds like epitalon, GHK-Cu |
This is a categorization convention researchers use to organize the field, not an endorsement of any claim about what a given compound does — see our compound-specific pages for what's actually documented about each.
Canadian regulation of peptides is compound-specific and has shifted meaningfully in 2026 — see our dedicated explainers for the current picture rather than relying on any general statement here: are peptides legal in Canada and what "research use only" actually means.
What is a peptide? A short chain of amino acids linked by peptide bonds — typically 2 to 50 amino acids.
How are peptides different from proteins? Size and structure — peptides are shorter, proteins longer and often more complex. The line is a convention, not a hard rule.
Are peptides drugs? Some are approved pharmaceuticals (insulin, GLP-1 medications). Others are sold as research chemicals. It depends on the specific compound, not the category.
Are peptides legal in Canada? It depends on the specific compound and how it's sold — see the dedicated legal explainer.
What does "research use only" mean? A regulatory label about intended use, not a safety grade — see the dedicated explainer.
For research and educational purposes only. Not medical advice.