Glossary
Every term, minus the jargon.
40 words that peptide guides throw around without explaining. Each one is defined in plain English, linked to its sources, and labeled by where the information came from.
Want the full walkthroughs? Read the guides0 to 9
A
B
C
- Certificate of analysis (COA)A document from a testing lab that reports what was measured in a sample: usually identity, purity and sometimes amount and contamination tests.
- Cold chainKeeping a product within a set temperature range at every step from maker to user: storage, shipping, and the trip home.
- Compounded vs brandedA branded drug is the FDA-approved product from its maker. A compounded drug is mixed by a pharmacy or outsourcing facility and is not FDA approved.
- CycleA set period of taking a compound, usually followed by a planned break. A protocol might say 8 to 12 weeks on, 4 weeks off.
D
E
F
G
- GHRHThe hormone from the hypothalamus that tells the pituitary to release growth hormone. Sermorelin, tesamorelin and CJC-1295 are GHRH analogs.
- GHRPA family of small synthetic peptides that trigger growth hormone release through the ghrelin receptor. GHRP-2, GHRP-6 and ipamorelin are examples.
- GIPA gut hormone that, like GLP-1, increases insulin release after meals. Tirzepatide acts on both the GIP and GLP-1 receptors.
- GLP-1A gut hormone that boosts insulin after meals, slows stomach emptying and reduces appetite. GLP-1 receptor agonists such as semaglutide copy and extend its effect.
- Glucagon receptorThe receptor for glucagon, a hormone that raises blood sugar and increases energy use. Retatrutide adds glucagon receptor activity to GIP and GLP-1.
H
- Half-lifeThe time it takes for the amount of a substance in the blood to fall by half. It largely decides how often a compound is dosed.
- HPLC purityThe share of the peptide signal in a sample that is the target peptide, measured by high-performance liquid chromatography. It is the percentage most COAs lead with.
I
- Injection site rotationMoving each shot to a new spot, and cycling across areas like the belly, thighs and arms, so no one patch of skin takes repeated injections.
- Insulin pen vs vialA pen is a prefilled cartridge with a dial that sets each dose. A vial holds liquid (or powder to mix) that you draw with a separate syringe.
- Intramuscular injectionA shot into muscle, such as the thigh, shoulder or glute. It needs a longer needle than a subcutaneous shot and is less common for peptides.
L
M
- Mass spectrometryA test that measures the mass of molecules. On a peptide COA it confirms identity: the measured mass should match the expected mass of the peptide.
- MicrodosingTaking a much smaller dose than the standard one, often a fraction of a starter dose. Common in GLP-1 communities for side effects, cost or maintenance.
N
P
- Peptide blendTwo or more peptides sold together in one vial, such as BPC-157 with TB-500. Every draw delivers all of them in a fixed ratio.
- Peptide stabilityHow long a peptide keeps its structure and strength. It depends on the molecule, whether it is dry or in solution, temperature, light and handling.
R
- ReconstitutionAdding a sterile liquid, usually bacteriostatic water, to a vial of freeze-dried peptide powder so it becomes an injectable solution with a known strength.
- Research use only (RUO)A label sellers put on compounds that are not approved drugs, stating they are sold for laboratory research and not for human use.
S
- SecretagogueAnything that makes a gland secrete a hormone. In peptide talk it almost always means a growth hormone secretagogue: a compound that prompts your own pituitary to release growth hormone.
- Sterile techniqueThe set of habits that keep germs out of a vial, syringe and injection site: clean hands, swabbed stoppers and skin, new needles, and never touching anything that should stay sterile.
- Subcutaneous injectionA shot into the fat layer just under the skin. It is the route most injectable peptides use, usually with a short, fine insulin needle.
T
U
- U-100 insulin syringeThe small insulin syringe most people use for peptides. Its scale is marked in units, where 100 units equals 1 mL, so 1 unit is 0.01 mL of liquid.
- Units vs mg vs mcgMilligrams (mg) and micrograms (mcg) measure how much peptide you take. Syringe units measure how much liquid you draw. You need the vial's concentration to convert one into the other.
V
W
- WADA S0The catch-all class on the World Anti-Doping Agency list: any substance with no current approval for human therapeutic use is banned in sport at all times, even if it is not named.
- WashoutTime off a compound so it clears the body before you start something else or measure your baseline. In trials it separates one treatment from the next.