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Peptide glossary: 30 terms explained in plain English

Lyophilised, bacteriostatic, subcutaneous, half-life, agonist — the vocabulary you'll run into when researching peptides, defined without jargon.

Peptide research has a vocabulary problem: half of it is clinical, half is forum slang, and nobody defines either. Here are the terms you'll actually encounter, in plain English. Nothing here is guidance — it's a dictionary.

The basics

• Peptide — a short chain of amino acids. Longer chains are proteins; the line between them is a matter of convention rather than chemistry.
• Amino acid — the building block. Sequence determines shape, and shape determines what a peptide interacts with.
• Sequence — the specific order of amino acids. Change the order and you have a different compound entirely.
• Analogue — a modified version of a naturally occurring peptide, usually altered to change stability or duration.

Form and preparation

• Lyophilised — freeze-dried. Water removed under vacuum, leaving a stable powder.
• Reconstitution — returning that powder to liquid form with a sterile diluent.
• Diluent — the liquid used to do it.
• Bacteriostatic water — sterile water with a preservative that inhibits bacterial growth.
• Sterile water — no preservative, therefore no protection after a vial is entered more than once.
• Blend — a single vial containing more than one peptide.
• Purity — the proportion of the contents that is the stated compound, usually established by HPLC testing.
• HPLC — high-performance liquid chromatography; the standard analytical method behind a purity figure.
• COA — certificate of analysis; the document reporting those test results.

Routes and administration

• Subcutaneous (SubQ/SC) — into the layer of fat beneath the skin.
• Intramuscular (IM) — into muscle tissue.
• Intranasal — via a nasal spray.
• Oral — swallowed; many peptides survive digestion poorly, which is why it's uncommon.
• Topical — applied to the skin, typical of cosmetic peptides.
• Site rotation — varying the location used, and the reason it's worth recording rather than remembering.
• U-100 syringe — an insulin syringe graduated in 100 units per millilitre.

Pharmacology

• Half-life — the time for the amount present in the body to fall by half. Longer half-life generally means less frequent administration.
• Agonist — binds a receptor and activates it.
• Antagonist — binds a receptor and blocks it.
• Dual agonist — activates two receptor types; the mechanism behind several newer metabolic compounds.
• Receptor — the cellular structure a compound binds to in order to have an effect.
• Bioavailability — how much of what's administered actually reaches circulation.
• Secretagogue — something that prompts the body to secrete a substance of its own rather than supplying it directly.
• Peptide bond — the chemical link joining amino acids in the chain.

Research and safety vocabulary

• In vitro — in a dish. Interesting, but a long way from a human result.
• In vivo — in a living organism.
• Preclinical — before human trials. A great deal of peptide literature stops here, which is worth remembering when reading claims.
• RUO (research use only) — labelled for laboratory research, not for human use.
• Contraindication — a reason something shouldn't be used in a given situation.
• Off-label — use outside a compound's approved indication.
• Placebo effect — improvement from expectation rather than from the compound. The main reason a consistent baseline in your own log is worth more than a strong first impression.

Want to see how these terms apply to specific compounds? Every entry in the A–Z reference uses this vocabulary in context, and the 3D library is the visual version of the same thing.

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Educational content only. Peptide Wizard does not calculate or recommend doses and is not medical advice — always consult a qualified healthcare professional.