Guide · glossary
A GLP-1 glossary, with the marketing words separated out
Some of these terms are pharmacology, some are law, and a few are sales language wearing the costume of the other two. Knowing which is which is most of what it takes to read a sales page in this market.
Updated 2026-08-239 sources
Every entry below links onward to the page where the term is used in context. Where a phrase is doing marketing work rather than describing something, that is said in the definition rather than left for you to notice.
The drugs
| Term | What it means |
|---|---|
| GLP-1 | Glucagon-like peptide-1, a hormone the gut releases after eating. It regulates appetite and calorie intake, and its receptor is present in brain regions involved in appetite. The drug class imitates it — How GLP-1 drugs actually work, and what that explains. |
| GLP-1 receptor agonist | A drug that binds and activates that receptor. Semaglutide is one. So, in part, is tirzepatide. |
| GIP | Glucose-dependent insulinotropic polypeptide — a second gut hormone. Tirzepatide activates both the GIP and GLP-1 receptors, which is what distinguishes it. Its label describes the evidence for GIP’s contribution to appetite as nonclinical. |
| Semaglutide | The molecule in Wegovy, Ozempic and Rybelsus. A peptide with 94% sequence homology to human GLP-1. |
| Tirzepatide | The molecule in Zepbound and Mounjaro, and the one with the largest average weight change of any approved agent in this class. |
| Orforglipron | An oral small-molecule GLP-1 receptor agonist sold as Foundayo — not a peptide, which is why it carries none of oral semaglutide’s food-and-water timing rules. See Pills or injections, now that the same drug comes as both. |
| Brand versus molecule | One molecule is usually sold under at least two brands at very different prices, with different approved indications. This is the single most expensive confusion in the market — Same molecule, different label, ten times the price and Every GLP-1 brand, and what each one is licensed for. |
How it is taken
| Term | What it means |
|---|---|
| Titration | Climbing the dose in fixed steps rather than starting at the treatment dose. Both labels say the purpose is to reduce gastrointestinal adverse reactions — Every dose step, and what to do when you miss one. |
| Starting dose | The first step on that ladder. For Zepbound the label states explicitly that the 2.5 mg starting dose “is not approved as a maintenance dosage.” Advertised prices frequently attach to this dose. |
| Maintenance dose | The dose you stay on, and the one whose price describes your actual annual cost. Usually more than one dose is approved as maintenance. |
| Microdosing | Deliberately staying below any approved dose. No label in this class describes it and no published trial result was produced at those levels — GLP-1 microdosing, and what the trials do not say about it. |
| Cold chain | Keeping the medicine within its temperature range from pharmacy to fridge. What happens when it breaks is in Shipping, storage and what happens when the box is late. |
Where the medicine comes from
| Term | What it means |
|---|---|
| Compounded | Made up by a pharmacy rather than manufactured and approved as a finished product. Compounded GLP-1s are not FDA-approved and have no approved indication — Brand-name vs compounded GLP-1s. |
| 503A pharmacy | A traditional compounding pharmacy, compounding against individual prescriptions. |
| 503B outsourcing facility | A facility registered with FDA that may compound in larger volumes. Registration is not approval of anything it makes. |
| 503B bulks list | The list of substances FDA has found a clinical need for outsourcing facilities to compound. In a notice published on 1 May 2026 FDA proposed not to include semaglutide, tirzepatide or liraglutide — which would remove the legal basis for most of the cheap tier. Not settled; see Brand-name vs compounded GLP-1s. |
| “FDA-registered facility” | A statement about a building, not about a medicine. FDA does not approve or license compounding pharmacies, and has sent warning letters to telehealth companies for implying otherwise — How to tell a regulated GLP-1 seller from a risky one. |
| Salt form | Semaglutide sodium or acetate, sold by some sellers as equivalent to the approved base. They are not the same active ingredient as the approved product. |
The money
| Term | What it means |
|---|---|
| Entry price | The lowest recurring medication price a provider publishes. Used for ranking on this site, and comparable only within a single market — The cheapest GLP-1 programmes, with the memberships added back in. |
| Membership fee | A subscription charge separate from the medication. Adding it back in changes the cheapest-provider ranking substantially. |
| Self-pay or cash price | What you pay without insurance, often through a manufacturer’s own channel. Frequently the cheapest lawful route to brand-name product. |
| List price | The undiscounted price of a package. Almost nobody pays it, and it is quoted mainly to make a discount look larger. |
| Prior authorisation | The insurer’s permission step before it will cover a drug. Whether a service will help with it is one of the thirteen checklist items — Thirteen things a GLP-1 service should tell you before you pay. |
| HSA / FSA | US tax-advantaged health accounts. Only 11 of 87 reviewed services say whether their charges qualify — Insurance, HSA and FSA for GLP-1s. |
| Formulary exclusion | A plan choosing not to cover a drug class at all. Coverage attaches to indications, not molecules, which is why the indication you meet matters — What else these drugs are approved to do. |
The rules
| Term | What it means |
|---|---|
| Indication | What a drug is approved to treat, as written on the label. Not what it can be prescribed for. |
| Off-label | Lawful prescribing outside the approved indication. Common and legitimate; it is the marketing of off-label use that is restricted. |
| Boxed warning | The most serious warning FDA applies. This class carries one for thyroid C-cell tumours, based on rodent data, with a contraindication for personal or family history of medullary thyroid carcinoma or MEN 2 — Who qualifies for a GLP-1, and what a real intake asks. |
| Accelerated approval | Approval on a surrogate marker rather than a hard outcome, with continued approval contingent on a confirmatory trial. The MASH indication is one — What else these drugs are approved to do. |
| Warning letter | A regulator’s written conclusion that something was wrong. A conclusion, not an allegation. |
| Complaint | An allegation that has not been decided. This site labels the two differently, and so should anything you read — How to tell a regulated GLP-1 seller from a risky one. |
| CAP Code rule 12.12 | The UK rule forbidding advertising a prescription-only medicine to the public. It is why British sites publish so few prices — Why UK GLP-1 pages tell you so much less. |
| GPhC | The General Pharmaceutical Council, whose public register is the fastest way to check a UK pharmacy. |
| MHRA | The UK medicines regulator, and the source of repeated warnings about unlicensed weight-loss pens sold online. |
| NICE | The body that decides what the NHS funds in England. Its appraisal of tirzepatide is TA1026. |
Reading a trial result
| Term | What it means |
|---|---|
| Placebo-adjusted | The drug result minus the placebo result. Always ask for both numbers — a good deal of what gets attributed to these drugs also happened on placebo, as The first year on a GLP-1, in the order things actually happen shows. |
| Estimand | The precise definition of the effect being estimated — including how people who stopped treatment are handled. Two figures from the same trial can differ purely on this. |
| MACE | Major adverse cardiovascular events: cardiovascular death, non-fatal myocardial infarction, non-fatal stroke. The endpoint behind semaglutide’s cardiovascular indication. |
| OSA | Obstructive sleep apnoea. An approved Zepbound indication, with its own higher maintenance doses. |
| MASH | Metabolic dysfunction-associated steatohepatitis, formerly NASH. An approved Wegovy indication for fibrosis stages F2 to F3, under accelerated approval. |
| Lean mass | Body mass that is not fat. Both labels say these drugs produce “greater fat mass loss than lean mass loss” — greater than, not instead of. |
| “Food noise” | A patient term, not a regulatory one. It appears in no label. What the labels describe is a physiological regulator of appetite acting on brain regions involved in appetite regulation. |
| “Nature’s Ozempic” | Marketing. No supplement in this category is a GLP-1 receptor agonist — GLP-1 supplements: what the label says, and what the evidence says. |
Questions
Is a compounded drug a generic?
No. A generic is an approved copy of an approved drug, held to bioequivalence standards. A compounded preparation is made by a pharmacy and is not FDA-approved at all. Liraglutide has genuine generics; semaglutide and tirzepatide do not.
What is the difference between Ozempic and Wegovy?
The same molecule, different brands, different approved indications and doses, and very different prices. The diabetes brands state on their own sites that they are not weight-loss drugs — Same molecule, different label, ten times the price.
Why does this site not score the researched reviews?
Because the rubric measures cancellation friction and clinical responsiveness, which cannot be assessed from a marketing page. Publishing a number nobody measured would be inventing an assessment — the methodology page sets out the reasoning.
Read next
- GuideStart here: which GLP-1 question are you actually asking?
- GuideHow GLP-1 drugs actually work, and what that explains
- ComparisonEvery GLP-1 brand, and what each one is licensed for
- ComparisonBrand-name vs compounded GLP-1s
- GuideThirteen things a GLP-1 service should tell you before you pay
- GuideWhat GLP-1s actually cost in 2026
- GuideMuscle loss on a GLP-1, and what the scans actually found
Sources
Everything on this page traces to one of the links below, retrieved on the date shown. Prices and programme terms in this market change without notice — confirm against the provider before you buy.
- 01WEGOVY® (semaglutide) injection and tablets — US prescribing information, Novo Nordisk, revised 06/2026retrieved 2026-08-23
- 02ZEPBOUND® (tirzepatide) injection — US prescribing information, Eli Lilly and Company, revised 04/2026retrieved 2026-08-23
- 03FDA — “Telehealth Companies: What to Know When Promoting Compounded Drugs” (cited from the search index)retrieved 2026-08-16
- 04FDA — “FDA Proposes to Exclude Semaglutide, Tirzepatide, and Liraglutide from the 503B Bulks List”, April 2026 (cited from the search index)retrieved 2026-08-16
- 05Federal Register — “List of Bulk Drug Substances for Which There Is a Clinical Need Under Section 503B”, notice 2026-08552, published 1 May 2026 (91 FR 23431), Docket FDA-2018-N-3240retrieved 2026-08-16
- 06ASA — Advertising advice, “Weight control: Prescription-only medicines”, setting out CAP Code rule 12.12retrieved 2026-08-16
- 07General Pharmaceutical Council — register of pharmacies and pharmacy professionalsretrieved 2026-08-16
- 08NICE — Technology appraisal TA1026, tirzepatide for managing overweight and obesityretrieved 2026-08-16
- 09MHRA — “MHRA urges public to avoid illegal online weight-loss medicines this New Year”, 29 December 2025retrieved 2026-08-16