Reference

Glossary

A plain-English translation of the jargon that comes up around GLP-1s, peptides, and clinical trials. Hover any underlined term inside an article to see the short version; come here for the full list.

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503ARegulation: Two FDA categories of compounding pharmacy. 503A pharmacies compound for individual prescriptions. 503B 'outsourcing facilities' operate under stricter, manufacturer-like oversight.

A

A1cLab values: A blood test that reflects your average blood sugar over the past ~3 months. The standard yardstick for diabetes control.
agonistPharmacology basics: A drug that turns a receptor ON, mimicking the body's natural signal. A 'GLP-1 agonist' activates the GLP-1 receptor the same way the GLP-1 hormone would.

B

bacteriostatic waterDosing: Sterile water with a tiny amount of benzyl alcohol added to slow bacterial growth, used to reconstitute multi-dose peptide vials.
BMILab values: Body Mass Index — weight divided by height squared. A crude population-level screen for obesity; not a great measure of any individual's body composition.
body compositionPhysiology: What your weight is made of — fat mass vs lean mass (muscle, bone, organs). Two people at the same weight can have very different body composition.

C

caloric deficitPhysiology: Eating fewer calories than you burn. Required for weight loss, but a deficit that's too aggressive on GLP-1s drives loss of muscle, not just fat.
cardiovascular eventConditions: A serious heart or vascular incident — heart attack, stroke, or cardiovascular death. Some GLP-1 drugs are approved specifically to lower the risk of these events.
compoundedRegulation: A medication custom-mixed by a licensed pharmacy rather than mass-produced by the brand-name maker. Quality and oversight vary a lot from one pharmacy to another.
contraindicationRegulation: A specific reason NOT to use a drug — a condition or other medication that makes it unsafe. GLP-1s are contraindicated in certain thyroid cancer histories, for example.

D

double-blindClinical trials: A study design where neither the participants nor the researchers know who is getting the real drug versus the placebo, which reduces bias.
dual agonistPharmacology basics: A drug that activates two receptors at once. Tirzepatide is a GLP-1/GIP dual agonist.

E

early satietySide effects: Feeling full after only a few bites. A common, usually-mild GLP-1 side effect driven by slowed gastric emptying.
energy expenditurePhysiology: How many calories your body burns over a given period. Glucagon-receptor activity (e.g. in retatrutide) is thought to nudge this upward.

F

FDA shortage listRegulation: An official FDA list of drugs in short supply. While a drug is listed, compounding pharmacies are temporarily allowed to prepare 'essentially copies' of it under specific conditions.
FDA-approvedRegulation: The U.S. Food and Drug Administration has reviewed trial data and cleared a specific molecule, dose, and formulation for a specific use. Approval attaches to the use, not the molecule in the abstract.
food noisePhysiology: Intrusive thoughts about food — cravings, planning meals, fixating on snacks. Many people report GLP-1 drugs quiet this background chatter; its return often precedes weight regain.

G

gastric emptyingPhysiology: How quickly the stomach moves food into the small intestine. GLP-1 drugs slow this down, which prolongs fullness but also causes nausea and reflux.
GIPHormones & receptors: Another gut hormone released after eating. It works alongside GLP-1 to help control blood sugar and may influence how the body handles fat.
GLP-1Hormones & receptors: A gut hormone your body releases after eating that nudges insulin up, slows stomach emptying, and tells your brain you're full. GLP-1 drugs mimic this hormone.
glucagonHormones & receptors: A hormone that raises blood sugar — insulin's counterpart. In drugs like retatrutide, activating the glucagon receptor is thought to increase energy expenditure.
glycemic controlPhysiology: How steadily blood sugar stays in a healthy range. The main goal of type 2 diabetes treatment, tracked with A1c and glucose readings.

H

half-lifePharmacology basics: How long it takes the body to clear half of a drug. A long half-life is why weekly GLP-1 injections work — the drug is still active days after the shot.

I

indicationRegulation: The specific condition the FDA has approved a drug to treat. The same molecule can be approved for one indication and used off-label for another.
insulinHormones & receptors: The hormone the pancreas releases to move sugar from the blood into cells. GLP-1 drugs nudge the pancreas to release insulin only when blood sugar is high.
intramuscularDosing: An injection into a muscle (e.g. deltoid, glute), deeper than subcutaneous. Most GLP-1 drugs are NOT given this way.
investigationalRegulation: A drug still being studied in trials and not yet approved by regulators. It can't legally be prescribed outside a trial setting.

L

lean massPhysiology: Everything in your body that isn't fat — mostly muscle. Aggressive caloric deficits on GLP-1s can cost lean mass alongside fat, which hurts long-term maintenance.
lipolysisPhysiology: The process of breaking down stored fat into fatty acids the body can burn for energy.

M

maintenance doseDosing: The steady long-term dose a person stays on after titration, once tolerability and response have stabilized.
metabolismPhysiology: The chemical reactions that turn food into energy. Despite the marketing, GLP-1s don't 'boost' metabolism — they reduce intake via appetite and gut signaling.

O

obesityConditions: A clinical category typically defined as BMI ≥ 30. The FDA label for Wegovy and Zepbound uses BMI thresholds plus weight-related conditions to define eligibility.
off-labelRegulation: When a doctor legally prescribes an FDA-approved drug for a use the FDA hasn't formally approved. Common and often evidence-based, but not the same as 'unapproved.'

P

pancreasPhysiology: The organ behind your stomach that makes insulin, glucagon, and digestive enzymes. It's a key target of GLP-1 signaling.
pancreatitisSide effects: Inflammation of the pancreas. A rare but serious GLP-1 side effect — classic sign is severe abdominal pain that radiates to the back, sometimes with vomiting or fever.
peptidePharmacology basics: A short chain of amino acids — basically a mini-protein. Many hormones (insulin, GLP-1) are peptides, which is why peptide drugs usually have to be injected rather than swallowed.
peptide bondPharmacology basics: The chemical link that joins one amino acid to the next, forming a peptide chain.
Phase 2Clinical trials: The middle stage of drug testing in humans — typically a few hundred patients, designed to find an effective dose and gather early efficacy data.
Phase 3Clinical trials: The large, late-stage trials (thousands of patients) used to confirm efficacy and safety before FDA approval. The last hurdle before a drug can be marketed.
placeboClinical trials: A fake treatment (saline injection, sugar pill) given to a control group so researchers can tell whether the real drug's effects are bigger than expectation alone.
prior authorizationRegulation: An insurance hurdle where your provider has to justify a prescription before the plan agrees to pay. Common for GLP-1s, especially for weight-loss indications.

R

receptorPharmacology basics: A protein on or inside cells that acts like a lock. When the right key (a hormone or drug) fits in, the cell does something — release insulin, feel full, etc.
reconstitutionDosing: Mixing a powdered drug with sterile liquid (usually bacteriostatic water) to make it injectable. Common with compounded peptides sold as vials of powder.
refluxSide effects: Stomach contents (and acid) backing up into the esophagus. More common on GLP-1s because the stomach empties more slowly.
research peptideRegulation: A compound sold for laboratory use only — not for humans. It is not FDA-regulated, not tested for human-grade purity, and not a legal shortcut to a prescription drug.
resistance trainingPhysiology: Exercise against load (weights, bands, bodyweight) that signals muscle to be preserved or built. The main non-pharmacologic lever to protect lean mass during GLP-1 weight loss.
retatrutideDrugs: An experimental injectable from Eli Lilly that activates three hormone receptors at once (GLP-1, GIP, and glucagon). Not yet FDA-approved.

S

semaglutideDrugs: A GLP-1 agonist sold as Ozempic (diabetes), Wegovy (weight loss), and Rybelsus (oral form for diabetes).
starter doseDosing: The low first dose used to let the body adjust to a drug. Not intended to drive results — just to limit side effects before escalation.
subcutaneousDosing: An injection into the fatty layer just under the skin (belly, thigh, upper arm) — not into a muscle or vein. This is how GLP-1 drugs are given.

T

tirzepatideDrugs: A weekly injection that activates both GLP-1 and GIP receptors. Sold as Mounjaro (type 2 diabetes) and Zepbound (weight loss).
titrationDosing: Gradually stepping the dose up (or down) over weeks so the body has time to adjust. Most GLP-1 drugs use titration to limit nausea.
trial armClinical trials: One group of participants in a clinical trial. A trial usually has several arms — for example, a placebo arm and one or more dose arms — so researchers can compare outcomes.
triple agonistPharmacology basics: A drug that activates three receptors at once. Retatrutide hits GLP-1, GIP, and glucagon together.
type 2 diabetesConditions: A chronic condition where the body doesn't respond well to insulin and blood sugar runs high. GLP-1 drugs were originally developed to treat it.