New to peptides? Start here.

What is a peptide?

A peptide is a short chain of amino acids — the building blocks of proteins — linked by peptide bonds. By common definition, a peptide is a chain of roughly 2 to 50 amino acids; longer unbranched chains are polypeptides, and larger folded structures are proteins [1]. Each unit in the chain is a “residue” [1]. Peptides occur naturally and act as hormones and signalling molecules in normal physiology [1].

Peptides as medicines

Because of that signalling role, peptides have been developed into approved medicines — more than 80 peptide drugs have reached the market worldwide for conditions including diabetes and osteoporosis, and peptides remain an active research area [2]. Familiar approved, prescription peptide medicines include insulin and the GLP-1 medicines such as semaglutide [2].

“Approved medicine” vs. “research peptide”

• Authorized medicines carry a DIN and are dispensed by prescription; they've been reviewed for safety, efficacy, and quality [3].
• “Research” peptides are compounds sold online, usually labelled “for research use only,” that have not been authorized by Health Canada — and, as our regulatory page explains, that label does not make them legal, exempt, or safe [3][4].

PeptideCheck helps you tell the difference and evaluate the documentation behind products in the second category. We don't sell peptides and we don't advise anyone to use them.

Glossary

• Amino acid — the basic building-block molecule of peptides and proteins [1].
• Peptide bond — the covalent bond linking amino acids into a chain [1].
• Residue — one amino-acid unit within a peptide chain [1].
• Certificate of Analysis (COA) — a batch-specific lab report of identity, purity, and sometimes contamination testing [5].
• HPLC — separates a sample's components to quantify purity [5][6].
• Mass spectrometry (MS) — measures molecular mass to confirm identity [5][6].
• Endotoxin / LAL assay — test for bacterial endotoxin contamination against pharmacopoeial limits [7][8].
• Lot / batch number — ties a product unit to a production run and its COA [5].
• DIN (Drug Identification Number) — the 8-digit number marking a Health-Canada-authorized drug [3].
• Lyophilised — freeze-dried.

FAQ

What's the difference between a peptide medicine and a “research peptide”?

A peptide medicine is authorized by Health Canada (has a DIN) and dispensed by prescription; a “research peptide” is an unauthorized compound sold online and is not a Health-Canada-approved medicine [2][3].

Does “for research use only” mean it's legal?

No. Health Canada has stated this label does not make a product legal or exempt, and advises against buying or using such products [4].

What makes a COA trustworthy?

A named, independent lab; a batch/lot number that matches the vial; identity (MS) and purity (HPLC) data; and a report you can verify on the lab's own website [5][6].

Is a high purity number enough?

No. Purity (HPLC) and identity (MS) don't measure endotoxin contamination, which needs a separate LAL test [7][8].

Do you sell peptides or recommend using them?

No. PeptideCheck is an independent information and vendor-assessment resource. We don't sell anything and we don't advise anyone to use these substances.

How do you make money?

From independent verification/testing services and educational work — never from selling peptides or selling ratings. See How we stay independent.