Plain-English definitions of the words you will see across this site and in peptide discussions. Jump to a letter, or use your browser’s find tool.
A · B · C · D · E · F · G · H · I · L · M · N · P · R · S · T · U · V · W
A
Acetic acid (0.6%): A weak acid solution sometimes used instead of bacteriostatic water to dissolve peptides that do not mix well in water.
Agonist: A compound that switches a receptor on. A GLP-1 agonist, for example, switches on GLP-1 receptors.
Amidate (amide): A small chemical cap added to the end of a peptide to protect it from breakdown, as in NA-Semax Amidate.
Amino acid: The building blocks of peptides and proteins. There are 20 standard amino acids.
Analog: A lab-made version of a natural molecule, changed slightly to last longer or work more strongly.
B
Bacteriostatic water (BAC water): Sterile water with 0.9% benzyl alcohol, a preservative that slows bacterial growth so a mixed vial can be used for several weeks.
Batch (lot) number: The code identifying a production run. It should match the batch on the certificate of analysis.
BDNF: Brain-derived neurotrophic factor, a natural protein that supports the growth and survival of nerve cells.
Bioregulator: A very short peptide, often two to four amino acids, from the Russian research tradition, aimed at supporting a specific organ.
Blend: Two or more peptides combined in one vial, such as BPC-157 with TB-500.
C
Certificate of analysis (COA): A lab report showing the identity, purity and amount of a specific batch. See Reading a COA.
Concentration: How much peptide is in each mL of mixed liquid. Vial mg ÷ mL of water.
Cycling: Using a peptide for a period, then taking a break.
D
DAC: Drug Affinity Complex, a chemical add-on that lets CJC-1295 bind to proteins in the blood and last for days.
Diluent: The liquid used to dissolve a powder, usually bacteriostatic water.
Dose: The amount of peptide taken at one time, usually in mcg or mg.
E
Endotoxin: A toxin from bacteria that can cause fever and reactions. Good COAs include an endotoxin test.
F
FDA-approved: Approved by the US Food and Drug Administration for at least one medical use. Entries on this site show this only when it applies.
G
GHRH: Growth hormone releasing hormone. GHRH analogs such as CJC-1295, sermorelin and tesamorelin prompt the pituitary to release growth hormone.
GHRP (ghrelin mimetic): Growth hormone releasing peptides such as ipamorelin and GHRP-2, which trigger growth hormone release through the ghrelin receptor.
GLP-1: Glucagon-like peptide-1, a gut hormone that reduces appetite and helps control blood sugar. Semaglutide and tirzepatide act on its receptor.
H
Half-life: The time it takes for half of a dose to be cleared from the body. It helps explain how often a peptide is dosed.
HPLC: High-performance liquid chromatography, the lab test used to measure purity.
I
IGF-1: Insulin-like growth factor 1, made mainly in the liver in response to growth hormone. It carries out many of growth hormone’s effects.
Injection site: The spot where a dose is injected. Rotating sites helps prevent irritation.
Insulin syringe: A small syringe marked in units. All calculations on this site assume U-100 insulin syringes.
Intramuscular (IM): An injection into a muscle.
IU (international unit): A unit based on biological activity rather than weight, used for HGH, HCG and oxytocin.
L
Loading phase: A higher starting dose used for a short time before dropping to a lower maintenance dose.
Lyophilized: Freeze-dried. Most peptides are supplied as a lyophilized powder, sometimes called a “puck.”
M
Maintenance dose: The ongoing dose after a loading phase or titration.
Mass spectrometry (MS): A lab test that weighs molecules to confirm a compound’s identity.
mcg (microgram): One thousandth of a milligram. 1,000 mcg = 1 mg.
mg (milligram): The unit most vials are labeled in. 1 mg = 1,000 mcg.
mL (milliliter): A unit of liquid volume. 1 mL = 100 units on a U-100 syringe.
N
Nasal spray: A route where the peptide is sprayed into the nose, used for several brain-focused peptides.
P
Peptide: A short chain of amino acids. Many act as signals that tell cells what to do.
PEG (pegylation): Attaching a polyethylene glycol chain to a peptide so it lasts longer, as in PEG-MGF.
Protocol: A plan for dose, frequency and length of use.
Purity: The share of the material that is the target compound, measured by HPLC.
R
Receptor: A protein on or inside a cell that a peptide binds to, triggering a response.
Reconstitution: Adding liquid to a powdered peptide so it can be measured. See the Reconstitution Guide.
S
Senolytic: A compound that helps clear senescent (“zombie”) cells, such as FOXO4-DRI.
Stack: Using two or more peptides together for complementary effects.
Subcutaneous (SubQ): An injection into the fat just under the skin, the most common route for peptides.
T
Titration: Starting with a low dose and increasing slowly to reduce side effects, standard with GLP-1 peptides.
U
U-100: The standard insulin syringe scale: 100 units = 1 mL.
Units: The markings on an insulin syringe. Units measure liquid volume, not the amount of peptide.
V
Vial: The small glass bottle a peptide comes in, sealed with a rubber stopper.
W
WADA: The World Anti-Doping Agency. Many peptides are on its prohibited list for competitive athletes.