Peptide Glossary: Terms Explained in Plain English

Mixing and measuring

Lyophilized — freeze-dried. The white powder/puck form peptides ship in, stable until water is added.

Reconstitution — dissolving the lyophilized powder in water to make an injectable solution.

Bacteriostatic water (BAC water) — sterile water with 0.9% benzyl alcohol, which stops bacterial growth in multi-use vials.

U-100 — the standard insulin syringe scale: 100 units per 1 ml. A 'unit' is a volume mark, not an amount of drug.

Concentration — how much peptide per volume, usually mg/ml or mcg per unit. Determined entirely by vial size and water amount.

Dead space — liquid trapped in a syringe hub/needle after injecting; wasted peptide unless using fixed-needle syringes.

Dosing language

mcg / mg — microgram and milligram; 1000 mcg = 1 mg. Most peptide doses are in mcg, most vials labeled in mg — the unit mismatch behind many errors.

Titration — starting low and raising the dose on a schedule, standard for GLP-1s to manage side effects.

Loading phase — a deliberately higher-frequency start (e.g., TB-500 twice weekly) before dropping to maintenance.

Cycling — running a compound for a set period then pausing, typically to protect receptor sensitivity.

Half-life — time for blood levels to fall by half; the reason CJC-1295 DAC is weekly while the no-DAC version is daily.

Subcutaneous (subq) — injection into the fat layer under the skin, the default route for peptides.

The GH axis

GHRH — growth hormone releasing hormone; analogs (sermorelin, CJC-1295, tesamorelin) amplify natural GH pulses.

Secretagogue / GHRP — compounds (ipamorelin, GHRP-2/6, hexarelin) that trigger GH release via the ghrelin receptor.

Somatostatin — the body's GH brake; part of why GHRH + secretagogue combos outperform either alone.

IGF-1 — the downstream growth factor GH stimulates; the blood marker used to verify GH-axis protocols are doing anything.

GH bleed — continuous moderate GH elevation (CJC-1295 DAC's pattern), as opposed to natural sharp pulses.

Metabolic and other

GLP-1 / GIP / glucagon receptor agonists — the incretin-axis weight-loss class: semaglutide (GLP-1), tirzepatide (dual), retatrutide (triple).

Amylin analog — cagrilintide's class; a separate satiety pathway stacked with GLP-1s.

Melanocortin — receptor family behind Melanotan II (tanning) and PT-141 (libido).

COA — certificate of analysis; third-party purity testing document reputable vendors publish per batch.

Research use only (RUO) — the legal designation for most compounds here: not approved for human use.