GLP-1 Glossary for Patients: 80 Terms, Explained Simply

Starting a GLP-1 medication means walking into three vocabularies at once. There is the clinical one your prescriber uses, the bureaucratic one your insurance plan uses, and the informal one everyone on Reddit uses. Nobody hands you a dictionary for any of them.

This is that dictionary. Terms are grouped by where you will run into them. Nothing here is medical advice, and none of these definitions tells you what to do — they tell you what the words mean so you can have a better conversation with a healthcare provider.

Last verified September 14, 2026.

The drugs and the class

GLP-1 (glucagon-like peptide-1). A hormone released by your small intestine after you eat. It tells the pancreas to release insulin, slows how fast the stomach empties, and reduces appetite. It breaks down in minutes naturally [1].

GLP-1 receptor agonist. A drug that switches on the same receptor the natural hormone uses. An “agonist” is anything that activates a receptor. This is the class semaglutide belongs to [1][5].

Semaglutide. The active ingredient in Ozempic and Wegovy. A lab-made peptide engineered to last about a week instead of minutes [1].

Ozempic. The semaglutide brand approved for type 2 diabetes, cardiovascular risk reduction and chronic kidney disease. Sold as a weekly injection and, since May 2026, as daily tablets [3].

Wegovy. The semaglutide brand approved for weight management, cardiovascular risk reduction and MASH. Sold as a weekly injection, as Wegovy HD 7.2 mg, and as a 25 mg daily tablet [2].

Rybelsus. The original oral semaglutide brand, retired in the US in 2026 and replaced by Ozempic tablets [4].

Wegovy HD. Semaglutide 7.2 mg once weekly, approved March 2026 for adults who have tolerated 2.4 mg for at least four weeks [13].

Tirzepatide. A different molecule, made by Eli Lilly, sold as Mounjaro and Zepbound. It is a dual GIP and GLP-1 receptor agonist. It is not semaglutide and the two are not interchangeable.

Orforglipron. Another different molecule, also Eli Lilly, sold as Foundayo. It is a small-molecule GLP-1 pill approved in April 2026 [12].

Liraglutide. An older, daily GLP-1 medicine sold as Victoza and Saxenda. Generic versions exist.

GIP (glucose-dependent insulinotropic polypeptide). A second gut hormone. Tirzepatide acts on both GIP and GLP-1 receptors; semaglutide acts only on GLP-1.

Amylin. A third hormone involved in fullness. Combination drugs in development pair an amylin analog with semaglutide.

Incretin. The umbrella term for gut hormones, including GLP-1 and GIP, that increase insulin release after eating.

Peptide. A short chain of amino acids. Semaglutide is a peptide, which is why it is injected rather than simply swallowed without help.

SNAC. Salcaprozate sodium, the absorption enhancer in oral semaglutide tablets that lets a peptide survive the stomach. It is the reason the pill has such specific instructions [4].

Taking the medicine

Titration. Stepping the dose up gradually on a schedule so the body can adjust. The whole point with GLP-1 drugs is reducing nausea [2][3].

Starting dose. A dose given to begin treatment that is not expected to do the full job on its own. Semaglutide 0.25 mg weekly is a starting dose, not a maintenance dose [2].

Maintenance dose. The dose you stay on once titration finishes.

Subcutaneous. Under the skin, as opposed to into a muscle or a vein. GLP-1 injections are subcutaneous, usually in the abdomen, thigh or upper arm [3].

Units. The markings on an insulin syringe. They are a volume measure, not a milligram measure, which is why converting a compounded vial into units requires knowing the concentration. Getting this wrong is a documented source of accidental overdose [11].

Concentration. How much drug is in each milliliter of liquid, written like 2.5 mg/mL. Two vials with the same milligram total can require completely different syringe volumes.

Pen. A prefilled injector, either single-dose or multi-dose. Pens must never be shared between people, even with a new needle [2].

Priming. Checking that a multi-dose pen is flowing before dialing your dose. Your product’s instructions for use say whether and how to do it.

Site rotation. Changing where you inject from week to week.

Beyond-use date (BUD). The date after which a compounded preparation should not be used. It is not the same as an FDA-approved product’s expiration date and is usually much sooner.

Half-life. How long it takes for half the drug to leave your body. Semaglutide’s is about one week, which is why it is dosed weekly and why it takes roughly five weeks to clear after the last dose [1].

Bioavailability. How much of a swallowed dose actually reaches your bloodstream. For oral semaglutide it is very low, which is why the empty-stomach and 30-minute rules exist [4].

Adherence and persistence. Adherence is taking the medicine as directed. Persistence is still being on it months later. Both matter enormously to real-world results.

Side effects and safety

Adverse reaction. An unwanted effect linked to a medicine. On a label these are grouped by how often they occurred in trials.

Boxed warning. The FDA’s strongest label warning. Every semaglutide product carries one about thyroid C-cell tumors observed in rodents [2].

Contraindication. A situation where a drug should not be used at all. Semaglutide has two: a personal or family history of medullary thyroid carcinoma or MEN 2 syndrome, and a prior serious allergic reaction to the drug [2].

Medullary thyroid carcinoma (MTC). A rare thyroid cancer named in the boxed warning and contraindication.

MEN 2. Multiple endocrine neoplasia syndrome type 2, an inherited condition that raises MTC risk.

Gastroparesis. Delayed stomach emptying severe enough to cause symptoms, sometimes called stomach paralysis. GLP-1 drugs slow emptying by design; in a minority of people it becomes a problem [3].

Ileus. When the intestine stops moving contents along. Listed in the postmarketing section of semaglutide labels [3].

Pancreatitis. Inflammation of the pancreas. The classic warning sign is severe abdominal pain that spreads to the back [2].

Cholecystitis and cholelithiasis. Gallbladder inflammation and gallstones. Both occur more often on semaglutide than placebo [2].

Dysesthesia. An abnormal skin sensation: tingling, burning or unusual sensitivity. It rose sharply at the 7.2 mg dose in the STEP UP trial, from 6.0 percent to 22.9 percent [19].

Eructation. The label word for burping. Online, the same thing is usually called sulfur burps.

NAION (non-arteritic anterior ischemic optic neuropathy). Sudden, usually painless, usually permanent vision loss in one eye caused by loss of blood flow to the optic nerve. European and UK regulators classify it as a very rare side effect of semaglutide; as of September 2026 the US label does not carry that warning [17].

Telogen effluvium. Temporary hair shedding triggered by a physical stressor such as rapid weight loss. It is the best current explanation for hair loss reported on GLP-1 drugs.

Hypoglycemia. Low blood sugar. Semaglutide alone rarely causes dangerous lows, but the risk rises sharply when combined with insulin or a sulfonylurea [2].

Sulfonylurea. An older class of diabetes pill that pushes the pancreas to release insulin. Named in the semaglutide interaction section for that reason.

Acute kidney injury. A sudden drop in kidney function. In GLP-1 reports it usually follows dehydration from severe vomiting or diarrhea [2].

Pulmonary aspiration. Stomach contents entering the lungs, a risk during anesthesia if food remains in the stomach after fasting. This is why every clinician should know you take a GLP-1 before any procedure [3].

Postmarketing. Reports collected after a drug is approved and in wide use. They can flag a signal but cannot by themselves prove the drug caused it.

Results and expectations

Percent body weight loss. The standard way trials report results, because losing 10 percent means something different at 180 pounds than at 300.

Plateau. A stretch where weight stops changing. In SELECT, weight loss continued to roughly week 65 and then held steady, so plateaus are expected rather than a sign of failure [18].

Weight regain. The return of lost weight after stopping. In the STEP 1 extension, about two-thirds of lost weight came back within a year of stopping.

Estimand. A technical trial term for which question the analysis is answering. The “treatment policy” estimand counts everyone including people who stopped; the “trial product” estimand counts people as if they had stayed on. This is why the same trial produces two different headline numbers, such as 18.7 percent and 20.7 percent for the same STEP UP result [19].

Lean mass. Everything in your body that is not fat, including muscle, water and organs. It is not the same as muscle, though the two are often used interchangeably.

DXA. A body scan that separates fat from lean tissue and bone. The source of most body composition claims about GLP-1 drugs.

Real-world evidence. Data from ordinary clinical care rather than a randomized trial. It usually shows smaller effects than trials, mostly because people stop earlier and use lower doses.

Bellwether trial. In mass litigation, an early test case whose result signals how others might go. None has been held in the GLP-1 cases as of September 2026 [20].

Money and insurance

List price (WAC). The wholesale acquisition cost the manufacturer sets before rebates. Almost nobody pays it [22].

Net price. What a payer actually pays after rebates and fees.

Cash price or self-pay price. What you pay without using insurance, including manufacturer direct prices.

Copay. Your fixed share of a covered prescription.

Coinsurance. Your share as a percentage instead of a flat amount.

Deductible. What you pay before the plan starts paying.

Formulary. The list of drugs your plan covers, usually organized into tiers.

Prior authorization. Approval your prescriber must get before the plan will pay. Close to universal for GLP-1 drugs.

Step therapy. A rule requiring you to try a cheaper drug first.

Appeal. Asking the plan to reconsider a denial. Most commercial plans also offer an external independent review once internal appeals are exhausted.

Copay card / savings card. A manufacturer discount for people with commercial insurance. People with Medicare, Medicaid or other government coverage are excluded.

Patient assistance program. A manufacturer program providing medicine at reduced or no cost to people who meet income and coverage criteria.

PBM (pharmacy benefit manager). The company that runs your plan’s drug benefit and negotiates rebates. The reason list price and what you pay are so far apart.

Medicare Part D. The Medicare prescription drug benefit.

Medicare GLP-1 Bridge. A CMS demonstration that began July 1, 2026 and runs through December 31, 2027, giving eligible Part D enrollees certain obesity medicines for a flat $50 monthly copay [14].

Maximum fair price. The price produced by Medicare drug price negotiation. CMS announced a headline figure of $274 for a 30-day supply of the semaglutide group beginning January 1, 2027; because the negotiation is per package, CMS’s own figures put Ozempic and Rybelsus near $276 and Wegovy near $385. A separate most-favored-nation agreement set a $245 Medicare price, and which one governs in 2027 is still unsettled [15].

Most-favored-nation (MFN) pricing. A policy of tying US prices to the lowest price paid in comparable countries.

TrumpRx. A federal website launched February 2026 that displays discounted cash prices and issues coupons you present at a pharmacy. It is not a pharmacy and its prices cannot be combined with insurance [16].

Regulation and manufacturing

FDA approval. The agency’s determination that a drug is safe and effective for a stated use.

Indication. A specific use a drug is approved for. A drug can have several.

Off-label. Using an approved drug outside its approved indication, age range or dose. Legal; rarely covered by insurance.

Accelerated approval. Approval based on a measure likely to predict benefit, with confirmation required later. Wegovy’s MASH indication was granted this way.

Tentative approval. An FDA finding that a generic meets all standards but cannot be marketed yet, usually because of patents or exclusivity. This is what a generic semaglutide injection received in April 2026, and it is not the same as a generic being available.

Generic. A copy that has proven equivalence to the brand and is FDA approved.

Biosimilar. The equivalent concept for large biologic molecules. Semaglutide is regulated as a drug, not a biologic, so its copies are generics.

Compounding pharmacy. A pharmacy that mixes customized medicines. Compounded drugs are not FDA approved and are not reviewed for safety, effectiveness or quality before sale [10][11].

503A. A traditional compounding pharmacy making preparations for individual patients with prescriptions.

503B outsourcing facility. A larger compounder that can make batches without individual prescriptions and is subject to more manufacturing oversight, but still does not produce FDA-approved drugs.

Drug shortage list. The FDA’s official list. While semaglutide was on it, compounding was far more permissible; that changed once supply stabilized [10].

Warning letter. An FDA notice that a company is violating the law. The agency has sent multiple rounds to telehealth companies marketing compounded GLP-1 products [11].

MDL (multidistrict litigation). A procedure that consolidates similar federal lawsuits before one judge. Two exist for GLP-1 drugs: one for gastrointestinal injuries, one for NAION [20].

Label / prescribing information. The FDA-approved document describing a drug’s uses, dosing, warnings and adverse reactions. It is the source of record, and it is public.

Community shorthand you will see online

These are not medical terms. They are what people actually write, and knowing them makes forums readable.

SW / CW / GW. Starting weight, current weight, goal weight.

Onederland. Dropping below 200 pounds.

Sulfur burps. Eructation with a rotten-egg smell.

Food noise. Intrusive, repetitive thoughts about food. Now the subject of published research [8][9].

Stall. A plateau.

Super responder. Someone who gets a strong effect at a very low dose.

Titrating up. Moving to the next dose step.

Microdosing. Using a dose below the labeled schedule, usually to save money or limit side effects. Not a labeled approach, and worth discussing with a prescriber rather than doing independently.

Compound / compounded sema. Compounded semaglutide.

Brand. FDA-approved manufacturer product, as opposed to compounded.

PA. Prior authorization.

Zep / Mounj / Tirz. Zepbound, Mounjaro, tirzepatide — all tirzepatide, none of them semaglutide.

Sources

1. Drugs.com, Semaglutide — https://www.drugs.com/semaglutide
2. FDA, Wegovy prescribing information — https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/215256s033lbl.pdf
3. DailyMed, Ozempic prescribing information — https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=adec4fd2-6858-4c99-91d4-531f5f2a2d79
4. FDA, oral semaglutide prescribing information — https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/213051Orig1s030lbl.pdf
5. Mayo Clinic, semaglutide (subcutaneous route) — https://www.mayoclinic.org/drugs-supplements/semaglutide-subcutaneous-route/description/drg-20406730
6. Cleveland Clinic, semaglutide injection for weight management — https://my.clevelandclinic.org/health/drugs/23611-semaglutide-injection-weight-management
7. MedlinePlus, semaglutide injection — https://www.medlineplus.gov/druginfo/meds/a618008.html
8. PMC, What is food noise? A conceptual model of food cue reactivity — https://pmc.ncbi.nlm.nih.gov/articles/PMC10674813
9. GoodRx, What is food noise — https://www.goodrx.com/health-topic/weight/what-is-food-noise
10. FDA, compounding policies as GLP-1 supply stabilizes — https://www.fda.gov/drugs/drug-alerts-and-statements/fda-clarifies-policies-compounders-national-glp-1-supply-begins-stabilize
11. FDA, concerns with unapproved GLP-1 drugs used for weight loss — https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
12. FDA, first new molecular entity approved under the National Priority Voucher program — https://www.fda.gov/news-events/press-announcements/fda-approves-first-new-molecular-entity-under-national-priority-voucher-program
13. FDA, higher-dose semaglutide approval announcement — https://www.fda.gov/news-events/press-announcements/fda-approves-fourth-product-under-national-priority-voucher-program-higher-dose-semaglutide
14. CMS, Medicare GLP-1 Bridge — https://www.cms.gov/medicare/coverage/prescription-drug-coverage/medicare-glp-1-bridge
15. CMS, negotiated prices fact sheet for 2027 — https://www.cms.gov/files/document/fact-sheet-negotiated-prices-ipay-2027.pdf
16. TrumpRx.gov — https://trumprx.gov/
17. EMA, PRAC conclusion on NAION — https://www.ema.europa.eu/en/news/prac-concludes-eye-condition-naion-very-rare-side-effect-semaglutide-medicines-ozempic-rybelsus-wegovy
18. PubMed, SELECT — https://pubmed.ncbi.nlm.nih.gov/37952131/
19. PubMed, STEP UP — https://pubmed.ncbi.nlm.nih.gov/40961953/
20. Drugwatch, Ozempic lawsuit status — https://www.drugwatch.com/legal/ozempic-lawsuit/
21. Peterson-KFF, prices of weight loss drugs in the US and peer nations — https://www.healthsystemtracker.org/brief/prices-of-drugs-for-weight-loss-in-the-us-and-peer-nations/