Glossary

What do all these words mean?

227 GLP-1 terms explained in plain English, from A1C and incretin to prior authorization and 503B, each with a source.

5 A B C D E F G H I K L M N O P Q R S T U W Y Z

5

503A pharmacy: A state-licensed pharmacy that can make a customized drug for one identified patient with a prescription. It does not need FDA approval or drug-manufacturing quality rules, and its products are never FDA-approved.Source
503B bulks list: The list of bulk ingredients outsourcing facilities may legally compound from. The FDA proposed in April 2026 to bar semaglutide, tirzepatide and liraglutide permanently; no final decision had been published as of September 2026.Source
503B outsourcing facility: A registered facility that can compound in bulk without patient-specific prescriptions, but must follow federal manufacturing quality rules and register with the FDA. Its GLP-1 shortage exemption ended in May 2025.Source

A

ACA Marketplace plan: Individual insurance bought through healthcare.gov or a state exchange. Coverage of obesity drugs is uneven and varies by plan and state.Source
Accelerated approval: FDA clearance based on a marker likely to predict benefit, with a confirmatory trial required afterward. Wegovy's MASH approval works this way, and its confirmatory data are not due until about 2029.Source
Acquired hypothalamic obesity: Severe, hard-to-treat obesity that follows damage to the hypothalamus, usually from a brain tumor or its treatment. It is the newest approved use for setmelanotide.Source
Active ingredient: The molecule that does the work. Ozempic and Wegovy share one active ingredient (semaglutide) but are different products with different approved uses and different doses.Source
Active, not recruiting: A ClinicalTrials.gov status meaning the trial is still running and still following participants, but has stopped enrolling. Several of the trials people most want answers from — SURMOUNT-MMO, the type 1 diabetes program, TRIUMPH-5 — sit in this state.Source
Adverse benefit determination: The legal name for a coverage denial. Federal rules require the notice to tell you the specific reason, the plan rule it relied on, how to get the internal criteria, and how to appeal.Source
Adverse reaction: A side effect recorded in a clinical trial, usually with a percentage and a placebo comparison. Nausea, for example, hit 44% on Wegovy 2.4 mg versus 16% on placebo.Source
Affiliate disclosure: A clear statement that a site earns money if you click or buy. The FTC requires it, and its 2024 rule also bans fake reviews and undisclosed insider testimonials.Source
Alternative funding program: A vendor a self-funded employer hires to move an expensive drug off the health plan. The plan excludes the drug, and the vendor tries to get it from a manufacturer assistance program, a charity or an overseas pharmacy instead.Source
Amylin: A hormone released alongside insulin that slows stomach emptying and adds to the feeling of fullness. Cagrilintide, petrelintide and eloralintide are lab-made amylin copies being tested for weight loss.Source
ANDA: The application used for a generic copy. It relies on the original drug's safety and effectiveness data and only has to prove sameness.Source
Anti-drug antibodies: Antibodies the immune system makes against an injected peptide drug. They appear in a substantial minority of people on tirzepatide, are reported in the label, and in the trials did not meaningfully change how well the drug worked.Source
Anti-obesity medication: The umbrella term for any drug approved for long-term weight management, from orlistat and phentermine/topiramate to the GLP-1 drugs. Insurers and state plans use it as the category they cover or exclude.Source
API: The raw drug substance before it becomes a finished product. The FDA created a GLP-1 "green list" of vetted suppliers and an import alert to keep unapproved foreign API out of the compounding market.Source
Apnea-hypopnea index (AHI): The number of times breathing stops or becomes shallow per hour of sleep, measured in a sleep study. It is the endpoint behind Zepbound's sleep apnea approval and the only apnea endpoint any drug in this class has ever hit.Source
Area postrema: A small brainstem region where the blood-brain barrier is naturally leaky. GLP-1 drugs reach it to create fullness — and it is also the brain's nausea trigger zone, which is why the two effects travel together.Source
Asynchronous prescribing: Getting a prescription from a questionnaire, with no live video or phone visit. Legal in some states and not others, and a recurring subject of state medical board attention.Source
Authorized generic: The brand-name drug itself, sold without the brand name and usually at a lower price, by the brand company or a partner. Teva's liraglutide is the clearest GLP-1 example.Source

B

Bariatric surgery: Weight-loss operations such as gastric sleeve or bypass. US volumes have fallen sharply since GLP-1 drugs arrived, and the drugs are also used for weight regain after surgery.Source
Bellwether trial: A test case tried early in an MDL to show both sides how juries react. Neither GLP-1 MDL had a bellwether date as of September 2026, so any settlement figure circulating online is speculation.Source
Biased agonism: The idea that two drugs hitting the same receptor can trigger different downstream signals. It is one unproven hypothesis for why tirzepatide produces more weight loss than semaglutide.Source
Bioavailability: How much of a dose actually reaches the bloodstream. Injected semaglutide is about 89% bioavailable; swallowed semaglutide is roughly 1%, which is why the pills need far larger milligram numbers.Source
Biosimilar: The near-copy pathway used for large biologic medicines. Semaglutide is regulated as a drug rather than a biologic, so its copies go through the generic pathway, not the biosimilar one.Source
BMI: Weight divided by height squared, used as a rough screening number. US labels use BMI 30 and above, or 27 and above with a weight-related condition, as the threshold for weight-management drugs — and insurers use the same cutoffs.Source
Boxed warning: The FDA's strongest label warning. Every semaglutide and tirzepatide product carries one for thyroid C-cell tumors seen in rodents, along with a hard ban on use by people with a personal or family history of medullary thyroid cancer or MEN 2.Source
Brand disambiguation: Mounjaro and Zepbound are the same molecule sold under two names with two labels, two sets of indications, two price ladders and two coverage worlds. Treating them as interchangeable is the single most common error in consumer coverage of tirzepatide.Source

C

Cardiovascular outcomes trial: A very large, years-long trial counting heart attacks, strokes and cardiovascular deaths rather than lab numbers. SELECT, SUSTAIN 6, SOUL and SURPASS-CVOT are the ones that matter here.Source
Chronic weight management: The FDA's phrasing for long-term obesity treatment, as opposed to a short diet course. It is the indication Wegovy and Zepbound carry, and the word "chronic" is doing real work: the trials show the weight returns when the drug stops.Source
Class action: One lawsuit brought on behalf of a whole group of people with the same complaint — distinct from an MDL, where each person keeps their own case.Source
Clinical obesity: A 2025 proposal to diagnose obesity by actual organ or function problems rather than BMI alone, splitting it from 'preclinical obesity' where excess fat is present but nothing is yet impaired.Source
Coinsurance: A percentage of the drug's price rather than a flat fee — brutal on a drug with a four-figure list price.Source
Compounded dosing error: Overdoses caused by confusing units — milligrams versus milliliters versus insulin-syringe "units" — when drawing compounded semaglutide from a vial. Poison-control reports include ten-fold overdoses.Source
Compounding: Making a drug by combining or altering ingredients, outside the FDA approval system. Compounded semaglutide is not an FDA-approved product and has not been reviewed for safety, effectiveness or quality.Source
Conference abstract: A short summary presented at a medical meeting such as ADA, ObesityWeek or ECO, often months or years before the full paper. Several 2026 findings in this corpus exist only in this form and are flagged as such.Source
Contraindication: A situation where a drug must not be used at all. For semaglutide: a personal or family history of medullary thyroid carcinoma or MEN 2, or a previous serious allergic reaction to the drug.Source
Copay: The fixed amount you pay per fill. The Medicare GLP-1 Bridge, for example, sets a $50 monthly copay for covered GLP-1 drugs.Source
Copay accumulator: A plan design that lets you use a manufacturer savings card at the pharmacy but does not count that money toward your deductible or out-of-pocket maximum. When the card's annual limit runs out mid-year, your cost jumps to the full amount all at once.Source
Copay card: A manufacturer coupon that cuts your out-of-pocket cost if you have commercial insurance. They are barred by law from being used with Medicare or Medicaid.Source
Copay maximizer: A plan design that raises your monthly share of the cost to exactly the amount a manufacturer card will cover, spreading the card evenly across the year. There is no sudden cliff, but the plan itself ends up paying nothing.Source
Counterfeit pen: A fake device made to look like a real one, sometimes carrying a genuine lot number. The FDA has seized counterfeit Ozempic three times since 2023, with some fakes containing insulin instead of semaglutide.Source

D

Deductible: What you pay before insurance starts contributing. Money you spend on a manufacturer self-pay program usually does not count toward it, which surprises people.Source
DEXA scan: The X-ray body-composition scan used in trials to split weight loss into fat, lean tissue and bone. It is the source of every "X% of the weight was muscle" figure you read.Source
Diabetic retinopathy: Damage to the blood vessels of the retina from diabetes. Rapid blood-sugar improvement can temporarily worsen it, which is why the semaglutide label carries a retinopathy precaution traced back to the SUSTAIN 6 trial.Source
Dietary Supplement Health and Education Act: The 1994 law that regulates supplements more like food than like drugs. Makers do not need FDA approval before selling, and the FDA generally can only act once a product is already on the market.Source
Direct-to-consumer pharmacy: A manufacturer selling straight to patients, bypassing insurance: NovoCare Pharmacy for Novo Nordisk products, LillyDirect for Eli Lilly.Source
Dose step-down: Dropping to a lower maintenance dose instead of stopping altogether. SURMOUNT-MAINTAIN tested a single fixed step-down to tirzepatide 5 mg held for a year. It is not the same thing as tapering, and no randomized taper study exists for any drug in this class.Source
DPP-4: The enzyme in your blood that chops up natural GLP-1 within about two minutes. Semaglutide is deliberately built to resist it, which is a large part of why one injection lasts a week.Source
Drug shortage list: The FDA's official list of drugs in short supply. Listing semaglutide in 2022 is what legalized mass compounding; the February 21, 2025 declaration that the shortage was resolved is what started shutting it down.Source
Dual GIP/GLP-1 receptor agonist: A drug that activates two gut-hormone receptors at once instead of one. Tirzepatide is the only one on the US market: a single 39-amino-acid peptide that hits both the GIP receptor and the GLP-1 receptor. Semaglutide hits only the GLP-1 receptor.Source
Dulaglutide: Eli Lilly's once-weekly GLP-1 drug for type 2 diabetes, sold as Trulicity.Source
Dysesthesia: Altered skin sensation — tingling, burning, sensitivity or pain. It showed up in 22% of people on the 7.2 mg Wegovy HD dose versus 6% at 2.4 mg, and the FDA has said it is still looking into it.Source

E

"Essentially a copy": The legal test that bars compounders from making near-identical versions of a commercially available approved drug. It is the central fight in the compounded-GLP-1 story, and it only relaxes while the drug is officially in shortage.Source
Efficacy supplement: An application asking the FDA to add or change what a label claims a drug does, backed by new clinical data. It is how Zepbound got sleep apnea and how Mounjaro got cardiovascular risk reduction — new indications on an existing approval rather than new drugs.Source
eGFR: An estimate of how well your kidneys filter blood. Sustained declines in eGFR were part of the composite endpoint in the FLOW kidney trial.Source
ERISA class action: A suit brought by health-plan members under the federal law governing employer benefit plans. Larkin v. Caremark RX is the GLP-1 example: members sued over the mid-year removal of Zepbound from a formulary.Source
Estimand: The rule for how a trial handles people who stop the drug or drop out. The "efficacy" estimand assumes everyone stayed on treatment; the "treatment regimen" estimand counts everyone as randomized. It is why one trial can honestly report two different weight-loss numbers.Source
Estimated primary completion date: The date a trial expects to finish collecting its main outcome — not the date results are published, which usually comes six months to two years later. Reading it as a readout date is the most common way trial timelines get reported wrong.Source
European Public Assessment Report (EPAR): The EMA's published dossier for an approved medicine: the assessment, the procedural steps and the current product information. It is the European counterpart to Drugs@FDA and the right source for an EU approval date.Source
Exclusivity: A period after approval when regulators will not clear a copy, separate from patents. Canada's expiry in January 2026 is part of why generic semaglutide arrived there years before it can arrive in the US.Source
Exenatide: The first GLP-1 drug, derived from a peptide in Gila monster venom and sold as Byetta and Bydureon. AstraZeneca discontinued both in the US in October 2024.Source
External review: The appeal stage after you have exhausted the insurer's own appeals: an independent reviewer outside the plan looks at the case and can overturn the denial. Some states run their own process; otherwise HHS runs a federal one.Source

F

FAERS / AEMS: The FDA's database of side-effect reports submitted by patients, doctors and companies, now called the Adverse Event Monitoring System. Reports are unverified and do not prove a drug caused anything, but clusters in them are how signals like NAION get noticed.Source
Fibrosis: Scarring of an organ, in this context the liver. MASH trials measure whether fibrosis improves without the inflammation getting worse.Source
Flexible spending account: An employer-run account you fund with pre-tax pay and spend on medical costs within the plan year. The same medical-necessity rules that govern HSA use of a GLP-1 apply here.Source
Food noise: The constant, intrusive mental chatter about food that many people describe. Quieting it is the single most common subjective effect people report on GLP-1 drugs, even before the weight changes.Source
Form 10-K: The annual report a US-listed company files with the SEC. It is the primary source for revenue, headcount, segment detail and legal proceedings — and the reason any company financial figure sourced to an aggregator instead should be treated as provisional.Source
Formulary: The list of drugs your plan covers, usually sorted into tiers with different copays. A drug that is "off formulary" is one you pay for entirely yourself unless you win an appeal.Source
Formulary exception: A request asking the plan to cover a drug that is not on its list, on the grounds that the covered alternatives will not work for you or would harm you.Source
Formulary exclusion: When a plan removes a drug entirely rather than putting it on a higher tier. The 2025 Zepbound exclusion at CVS Caremark is the best-known GLP-1 example.Source
Foundayo: The brand name for orforglipron, the first small-molecule GLP-1 pill approved for obesity, launched in April 2026.Source

G

Gastric emptying: How fast food leaves your stomach. Semaglutide slows it, mostly in the first hour after eating, which contributes to fullness and to nausea, and is the reason for the anesthesia precautions.Source
Gastroparesis: Severely delayed stomach emptying, causing vomiting, bloating and fullness that does not pass. It is the core injury claimed in the MDL 3094 lawsuits, and published evidence on whether it reverses after stopping is thin.Source
Generic drug: A copy of an approved drug, made by another company after patents and exclusivity lapse, reviewed by the FDA for sameness. Generic liraglutide exists in the US; generic semaglutide does not, though it is on sale in Canada and India.Source
GIP: The second incretin hormone. Tirzepatide (Mounjaro, Zepbound) switches on the GIP receptor as well as the GLP-1 receptor, which is the main molecular difference between it and semaglutide.Source
GIP receptor (GIPR): The cell-surface receptor for GIP, found on fat cells, pancreatic islet cells and in parts of the brain. Tirzepatide activates it; semaglutide does not. Confusingly, drugs that block this receptor also produce weight loss, and nobody has yet explained why both directions work.Source
GLP-1: A hormone your small intestine releases within minutes of eating. It tells the pancreas to release insulin when blood sugar is high, tells the liver to stop dumping sugar, slows how fast the stomach empties, and signals fullness to the brain. Natural GLP-1 is destroyed in about two minutes; the drugs are engineered copies that last much longer.Source
GLP-1 booster: A supplement marketed as raising your own GLP-1 levels. The usual ingredients are fibers and plant extracts with small satiety effects at best, and the claims are largely unreviewed by any regulator.Source
GLP-1 microdosing: Taking doses below the labeled schedule, heavily marketed by compounders and telehealth sellers. No randomized trial supports it, and the doses in the trials are the doses in the label.Source
GLP-1 receptor agonist: Any drug that switches on the GLP-1 receptor, imitating the natural hormone. Semaglutide, liraglutide, dulaglutide, exenatide and orforglipron are all GLP-1 receptor agonists. Tirzepatide hits the GLP-1 receptor plus a second one.Source
Glucose-dependent: Means the drug only pushes insulin when blood sugar is already high, easing off as sugar falls. It is why semaglutide alone rarely causes low blood sugar, unlike insulin.Source
Gold carding: An insurer policy that exempts clinicians with a consistently high approval rate from having to file prior authorizations at all, for a set period and for named services. Six states have passed gold-carding laws.Source

H

Half-life: How long it takes your body to clear half of a drug dose. Semaglutide's is about one week, which is why it is injected weekly and why it takes roughly five weeks to wash out after the last dose.Source
HbA1c: A blood test showing your average blood sugar over roughly the past three months, reported as a percentage. It is the main endpoint in every diabetes trial in this field; semaglutide typically lowers it by about 1.5 percentage points.Source
Health savings account: A tax-advantaged account paired with a high-deductible health plan. A GLP-1 prescribed to treat a diagnosed condition is an eligible expense; for general weight loss the IRS usually expects a letter of medical necessity.Source
HFpEF: A form of heart failure where the heart pumps normally but cannot fill properly. Semaglutide improved symptoms and physical limitation in the STEP-HFpEF trials.Source
Hypoglycemia: Blood sugar falling too low. Semaglutide alone rarely causes it because its insulin effect is glucose-dependent, but the risk rises sharply when it is combined with insulin or sulfonylureas.Source

I

Ileus: A stall in the normal movement of the intestines, which can be a medical emergency. It appears in the postmarketing section of the semaglutide label.Source
Import Alert: An FDA order letting inspectors detain a category of imported product without physically examining it. GLP-1 active ingredients from unregistered foreign suppliers sit under one, which is what makes the gray-market peptide supply chain illegal rather than merely unregulated.Source
In-use storage window: How long a pen or vial stays usable once you have started it, which is shorter than the shelf life of an unopened one and differs by device. Reading the number for the wrong device is a common mistake.Source
Incretin: A gut hormone released after eating that boosts insulin release. GLP-1 and GIP are the two main human incretins. "Incretin drug" is the umbrella term for this whole class of medicines.Source
Incretin effect: The discovery that swallowing glucose produces far more insulin than putting the same amount of glucose straight into a vein. That gap is what told researchers gut hormones must exist, and it is the reason this entire drug class exists.Source
Incretin market share: A company's share of total US prescriptions for GLP-1 and dual-agonist drugs, usually measured by IQVIA and quoted by the manufacturer. Lilly last published a figure — 60.1% — in its Q1 2026 deck, on four-week rolling data to March 27, 2026.Source
Indication: A specific condition a drug is approved to treat, spelled out in section 1 of the label. Semaglutide products carry different indications even though the molecule is identical.Source
Internal appeal: Your formal request that the insurer reconsider its own denial, with deadlines set by federal claims rules. It has to be exhausted before an external review can be requested.Source
International price gap: The difference between US and other rich-country prices. The most-cited comparison found a month of Ozempic listed around $936 in the US against roughly $169 in Japan and about $93 to $103 in the UK and Germany — figures from 2023 that are now dated.Source

K

KwikPen: Lilly's single-patient-use multi-dose injection pen. The tirzepatide KwikPen holds four weekly doses in one device, so one pen lasts a month. It is a different presentation from the single-dose pen and the vial, and it carries its own savings-card terms.Source

L

Label / prescribing information: The FDA-approved document that defines what a drug is approved to treat, at what doses, with what warnings. In this repository the label outranks every press release and news story.Source
Lanham Act claim: The federal false-advertising cause of action companies use against each other. It is what Novo Nordisk brought against Eli Lilly in July 2026, and what Lilly brought against several compounders — in the Empower case, those claims were dismissed while state-law claims survived.Source
Lean mass: Everything in your body that is not fat, including muscle. Roughly a quarter to 40% of the weight lost on semaglutide is lean tissue, which is normal for weight loss but matters more for older adults.Source
Letter of medical necessity: A letter your prescriber writes to argue that a specific drug is medically necessary for you. It names the drug, strength and duration, gives the diagnosis and ICD-10 codes, lists what you already tried and why it failed, and cites the clinical evidence.Source
LillyDirect: Eli Lilly's direct-to-consumer channel: a website where people can get a telehealth prescription and buy Zepbound, Mounjaro or Foundayo at a published self-pay price, shipped by a partner pharmacy or picked up at Walmart. It is how most cash-paying tirzepatide patients now buy.Source
Lipase inhibitor: A drug that blocks the gut enzyme that digests fat, so some of the fat you eat passes through undigested. Orlistat is the only one on the US market, and its side effects are all digestive.Source
Liraglutide: The once-daily GLP-1 drug that came before semaglutide, sold as Victoza for diabetes and Saxenda for weight loss. Now also available as a US generic.Source

M

MACE: The bundled trial endpoint of cardiovascular death, heart attack and stroke. Semaglutide cut it by 20% in the SELECT trial, which is what earned Wegovy its heart indication.Source
Maintenance dose: The dose you stay on after finishing the step-up schedule — 2.4 mg weekly for Wegovy, for example. Some people stop at a lower dose if that is what they tolerate.Source
MASH: A fatty liver disease with inflammation and scarring, formerly called NASH. Wegovy won accelerated approval for it in August 2025.Source
Maximum fair price: The price Medicare negotiates directly with a manufacturer under the Inflation Reduction Act. Ozempic, Rybelsus and Wegovy were selected in January 2025, with the negotiated price effective January 1, 2027.Source
MC4R agonist: A drug that acts on the brain's melanocortin-4 receptor, a different appetite pathway from GLP-1. Setmelanotide is the approved example, and it only works for rare genetic and acquired forms of obesity.Source
MDL: A federal system that gathers similar lawsuits from around the country before one judge for pretrial work. MDL 3094 handles GLP-1 stomach injury claims; MDL 3163 handles NAION vision-loss claims.Source
Mediation analysis: A statistical attempt to work out how much of a drug's benefit runs through one pathway — for example, how much of tirzepatide's sleep apnea benefit is explained by weight loss alone. It is an inference from trial data, never a direct measurement.Source
Medicaid: The joint federal-state program for people with low incomes. Whether it covers GLP-1 drugs for obesity is a state-by-state choice, and several states have added and then dropped coverage as budgets moved.Source
Medical expense deduction: The itemized tax deduction for unreimbursed medical costs above a set share of your income. GLP-1 costs can count when the drug treats a diagnosed disease rather than general health.Source
Medicare GLP-1 Bridge: The CMS demonstration that started July 1, 2026, offering Medicare beneficiaries covered GLP-1 drugs at $50 a month. It is scheduled to end December 31, 2027.Source
Medicare Part D: Medicare's outpatient prescription benefit. By statute it cannot cover drugs used for weight loss, which is why Medicare coverage of semaglutide depends on a second indication such as heart-risk reduction, or on a special demonstration.Source
Medicare Prescription Payment Plan: A Part D option that spreads your out-of-pocket drug costs into capped monthly bills from the plan instead of large payments at the pharmacy counter. It changes the timing, not the total.Source
Meta-analysis: A study that statistically pools many earlier studies. Useful for rare effects, but only as good as the studies inside it.Source
Missed dose rule: What the label tells you to do if you skip an injection. For Ozempic, take it within 5 days of the missed day; after that, skip it and resume the normal schedule. The rules differ for Wegovy and for the tablets.Source
Most-favored-nation pricing: A deal tying US prices to the lowest price a drugmaker charges in comparable wealthy countries. The November 2025 agreements with Novo Nordisk and Eli Lilly set a $245 Medicare price for GLP-1 drugs in exchange for tariff relief and priority review vouchers.Source
Mounjaro: Eli Lilly's tirzepatide injection for type 2 diabetes, and since December 2025 for children aged 10 and older.Source
Multi-dose pen: A pen holding several weekly doses that you dial and reuse. Never share one, even with a new needle, because of blood-borne infection risk.Source
Multi-dose vial: A four-dose tirzepatide vial approved for both Zepbound and Mounjaro on January 7, 2026, with full NDC numbers in both labels. As of September 2026 no retail or direct channel had been found actually selling one for either brand.Source

N

NAION: Sudden, usually painless vision loss in one eye caused by an interrupted blood supply to the optic nerve. European, UK, Australian and WHO regulators added it to semaglutide labeling; US labels still did not carry it as of September 2026.Source
National Drug Code: The eleven-digit code that identifies a specific drug product, strength and package size. Pharmacy counters, savings cards and coverage programs all key off it, so the right NDC is what makes a discount actually apply.Source
National priority voucher: An FDA pilot that compresses review from months to weeks for selected products. Wegovy HD was cleared in 54 days under it in March 2026; Foundayo followed.Source
Nature's Ozempic: A marketing phrase attached to berberine and other supplements since 2023. Nothing sold under it is a GLP-1 receptor agonist, and none of it produces weight loss anywhere near the prescription drugs.Source
NCT number: The unique registry ID for a clinical trial on ClinicalTrials.gov, such as NCT03548935 for STEP 1. If a trial has no NCT number, treat every claim about it carefully.Source
NDA: The application a company files to get a new drug approved, and the number that identifies it forever after. Ozempic is NDA 209637; Wegovy is NDA 215256.Source
NDC number: The National Drug Code printed on every US drug package — the unique identifier for that exact product, strength and package size. Checking it is one way to verify a pen is genuine.Source
Net price: What the manufacturer actually keeps after rebates to insurers and pharmacy benefit managers. The gap between list and net is why a "50% price cut" may change very little for a covered patient.Source
Non-inferiority: A trial design asking only whether a new drug is not meaningfully worse than an existing one. CagriSema failed a non-inferiority test against tirzepatide in REDEFINE 4 in February 2026.Source
Notice of Compliance: Health Canada's equivalent of an FDA approval letter. Canadian approval dates for tirzepatide products are frequently quoted from company press releases rather than the Notice of Compliance itself.Source

O

"Ozempic babies": Unexpected pregnancies during GLP-1 treatment, attributed to restored ovulation with weight loss and, for the oral products, reduced absorption of the contraceptive pill. No study has ever measured how often it actually happens.Source
"Ozempic face": The hollowed, older-looking face that can follow fast weight loss. It is a consequence of losing facial fat quickly, not a drug-specific effect — any rapid weight loss can do it.Source
Obesity as a chronic disease: The framing behind these approvals: obesity as a long-term medical condition requiring ongoing treatment rather than a temporary willpower problem. It is what makes indefinite drug therapy a coherent plan rather than a failure.Source
Obstructive sleep apnea: Repeated airway collapse during sleep. Tirzepatide (Zepbound) is the only drug approved for it; no semaglutide trial has ever used the standard sleep-apnea measurement as its main endpoint.Source
Off-label use: Prescribing an approved drug for something outside its approved uses — legal for doctors, but unstudied territory. Using Ozempic purely for weight loss is the most common example.Source
Oral contraceptive interaction: Tirzepatide slows stomach emptying enough to change how much of a swallowed birth control pill is absorbed, so the label advises a backup method or a switch to a non-oral contraceptive around starting and each dose increase. All the evidence is pharmacokinetic; no trial has counted pregnancies.Source
Orange Book: The FDA's public list of approved drugs with their patents and exclusivity periods. It is the authoritative answer to "when can a generic launch" — and the reason any patent-expiry date not traced to it should be treated as secondhand.Source
Orforglipron: Eli Lilly's once-daily GLP-1 pill, sold as Foundayo since April 2026. It is a small molecule rather than a peptide, so it can be swallowed with or without food and needs no special waiting period.Source
Out-of-pocket cap: The annual ceiling on what you pay yourself. Medicare Part D now has one, which changed the arithmetic for expensive drugs like semaglutide.Source
Ozempic: The once-weekly semaglutide injection approved for type 2 diabetes, heart-risk reduction in people with diabetes and heart disease, and slowing kidney disease. It is not approved for weight loss, even though it causes it.Source
Ozempic tablets: The reformulated, better-absorbed oral semaglutide (1.5, 4 and 9 mg) that replaced Rybelsus in US pharmacies in May 2026. It is not interchangeable milligram-for-milligram with Rybelsus.Source

P

Pancreatitis: Inflammation of the pancreas, usually felt as severe upper abdominal pain that may radiate to the back. The label tells prescribers to stop the drug if it is suspected.Source
Patent cliff: The moment a drug's protection lapses and copies flood in. Semaglutide's protection fell in Canada, India, China and Brazil during 2026; core US compound patents run to December 2031.Source
Patient assistance program: A manufacturer program giving free or heavily discounted medicine to people who meet income rules and have no adequate coverage.Source
PBM: The middleman that runs your drug benefit — building the formulary, negotiating rebates and setting copays. CVS Caremark's 2025 decision to prefer Wegovy and drop Zepbound moved hundreds of thousands of patients between drugs overnight.Source
PDUFA date: The target date by which the FDA aims to decide on an application. CagriSema has no published PDUFA date, which is why every "expected Q4 2026" line in coverage is an estimate.Source
Pediatric indication: FDA approval to use a drug in children, granted only on pediatric trial data. Mounjaro has one, for type 2 diabetes in children 10 and older. Zepbound does not have one for adolescent obesity, and the two are easily confused.Source
Peer-to-peer review: A phone call between your prescriber and a clinician working for the insurer, to argue the medical case directly. It is usually offered alongside or right after a denial, and many states require the insurer's reviewer to be in the same specialty.Source
Pen needle: The short, single-use needle that screws onto an injector pen. It is dispensed separately from the drug in the US, so a prescription for the pen does not automatically get you needles.Source
Peptide: A short chain of amino acids — a mini-protein. Semaglutide is a peptide, which is why it is usually injected: your gut digests peptides.Source
Perioperative guidance: The rules for GLP-1 drugs around surgery. Because the drugs slow stomach emptying, there is an aspiration risk under anesthesia; 2024 multisociety guidance replaced blanket "stop the drug" advice with a case-by-case approach.Source
Persistence and adherence: How long people keep taking a drug and how closely they follow the schedule. Roughly half of people starting a GLP-1 for weight loss are no longer on it a year later.Source
Personal importation: Buying medicine from another country for your own use. The FDA generally treats it as illegal, with narrow discretion, and warns that imported GLP-1 products are a common route for counterfeits.Source
Pharmacovigilance: The ongoing monitoring of a drug's safety after approval. Novo Nordisk received an FDA warning letter in March 2026 for reporting adverse events late.Source
Phase 3 trial: The large, usually final stage of testing before an approval filing. STEP, SUSTAIN, SURMOUNT and REDEFINE are all phase 3 programs.Source
Placebo: The dummy treatment given to a comparison group. Every headline weight-loss number should be read against its placebo arm — for STEP 1 that was 14.9% versus 2.4%.Source
Preconception washout: How long to stop a drug before trying to conceive. Tirzepatide has no US-labeled interval; the one-month figure circulating online comes from Canadian labeling, and the US label simply says to discontinue when pregnancy is recognized.Source
Preemption: A defense arguing that because the FDA approved the label, state-law failure-to-warn claims cannot proceed. It is one of the two big questions still pending in MDL 3094.Source
Preprint: A paper posted publicly before peer review, for example on medRxiv. This repository deliberately excludes preprint-only findings from its main claims.Source
Prescribing information vs marketing claim: The difference between what the FDA-approved label says and what an ad says. When the two conflict, the label wins — and the FDA can and does send letters over the gap.Source
Preserved vs preservative-free formulation: Multi-dose presentations need a preservative so the vial or cartridge stays sterile once it has been entered more than once; single-dose pens and vials do not. It is why the KwikPen and the multi-dose vial are not chemically identical to the single-dose pen.Source
Primary endpoint: The single result a trial was designed to measure. Everything else is secondary and should be read more cautiously — "missed its primary endpoint" is the phrase that sinks a drug.Source
Prior authorization: The paperwork your prescriber must file before insurance will pay. For GLP-1 weight-loss coverage it typically requires a BMI threshold, documented diet attempts, and sometimes proof you failed a cheaper drug first.Source

Q

Quantity limit: A cap on how much of a drug a plan will pay for in a given period — for a GLP-1 usually four pens or one month at a time. Exceeding it needs a separate exception request.Source

R

Randomized controlled trial: A study where participants are assigned to treatment or comparison by chance, which is what allows a cause-and-effect claim. It is the highest standard of evidence in this corpus.Source
Randomized withdrawal trial: A trial design where everyone takes the drug first, then some are switched to placebo. SURMOUNT-4 and STEP 4 both used it, which is why we know what happens when people stop: most of the weight comes back.Source
Real-world evidence: Findings from medical records, claims or pharmacy data rather than a controlled trial. Real-world weight loss is consistently smaller than trial weight loss, mostly because people stop the drug or never reach the full dose.Source
Reauthorization: The periodic re-approval an insurer requires to keep paying for a drug, usually every 6 or 12 months. GLP-1 reauthorization criteria can require documented ongoing weight loss, so hitting your goal can end coverage.Source
Rebate: A payment from a drugmaker back to a pharmacy benefit manager or insurer in exchange for formulary placement. Rebates are confidential, which is why nobody outside the deal knows the real price of a GLP-1.Source
Refill rule: The minimum interval a self-pay or savings program allows between fills. Zepbound's is 45 days for a month's supply, which is why people who order early find the price or the card rejected.Source
Research-use-only peptide: Vials of peptide sold online labeled "not for human consumption" as a legal fig leaf. They are unapproved, unregulated and increasingly the target of FDA warning letters.Source
Rule 702 hearing: The hearing where a judge decides whether each side's expert witnesses may testify at all. In MDL 3094 the hearing opened September 14, 2026; a ruling against the plaintiffs' experts would effectively end most of those cases.Source
Rybelsus: The original semaglutide tablet (3, 7 and 14 mg) for type 2 diabetes, taken fasting with a sip of water and a 30-minute wait. The brand name was retired in 2026 in favor of Ozempic tablets.Source

S

Sarcopenia: Age-related loss of muscle mass and strength. Whether GLP-1 drugs accelerate it in older adults is an open question; no trial designed around muscle and physical function in people over 65 has reported.Source
Savings card tier: Manufacturer copay cards usually have two tiers: a low one if your plan covers the drug, and a higher one if it does not. Lilly runs separate cards for the Zepbound single-dose pen, the Zepbound KwikPen and Mounjaro, and all of them expire December 31, 2026.Source
Section 337 / ITC exclusion order: A US International Trade Commission proceeding that can block imports of infringing goods. Lilly used one against imported tirzepatide material; it works at the border rather than through a damages award.Source
Self-funded plan: An employer plan that pays claims out of the employer's own money, with an insurer hired only to administer it. These plans are governed by federal ERISA law, so state coverage mandates generally do not apply to them.Source
Self-pay / cash price: The price when you skip insurance entirely and buy direct. Novo Nordisk sells through NovoCare Pharmacy and Eli Lilly through LillyDirect, with 2026 semaglutide prices between roughly $149 and $499 a month depending on product and dose.Source
Self-pay price: The price a person pays with no insurance involved, set by the manufacturer rather than by a pharmacy benefit plan. For Zepbound it is a published ladder that rises with dose; for Mounjaro, Lilly lists a single flat monthly figure at every dose.Source
Semaglutide: The active ingredient in Ozempic, Rybelsus, Ozempic tablets, Wegovy and Wegovy tablets. It is a 31-amino-acid copy of human GLP-1 with three engineered changes that let one dose last about a week.Source
Semaglutide sodium / semaglutide acetate: Salt forms of semaglutide that have turned up in compounded products. The FDA treats them as different active ingredients from the semaglutide base in the approved drugs, so they are not approved for any use.Source
Sharps container: A rigid, puncture-resistant, leak-proof container with a tight lid for used needles and pens. The FDA says to use an FDA-cleared container where possible, and a heavy-duty plastic household container as a fallback.Source
Sharps disposal: The two-step method for getting rid of used pens and needles: put them straight into a sharps container, then dispose of the full container by whatever route your state allows. Never put loose needles in household trash or recycling.Source
Signal: A pattern in safety reports suggesting a possible new risk, not yet proven. NAION was a signal for about 18 months before European regulators concluded it was a very rare real side effect.Source
Single-dose pen: A pen containing one dose, used once and thrown away. Wegovy launched this way; Ozempic uses multi-dose pens instead.Source
Single-dose vial: A small glass vial holding one week's tirzepatide dose, drawn up with a separate syringe. It is the cheapest Zepbound presentation on LillyDirect and the reason the self-pay price ladder has a low rung.Source
Small molecule: A conventional chemical drug small enough to survive digestion and be swallowed easily. Orforglipron is the first small-molecule GLP-1 drug, which is why it has no food or water restrictions.Source
SNAC: The absorption helper mixed into oral semaglutide tablets. It temporarily changes conditions in the stomach so a small fraction of the peptide can get through the stomach wall instead of being digested.Source
sNDA / supplement: The filing used to add a new use, dose or label change to an already-approved drug. Almost every "FDA approves Ozempic for X" headline is a supplement approval, not a new drug.Source
Starting dose: The first, lowest dose. For the oral products the label says plainly that the starting dose is not effective for blood sugar control; it exists only to let your body adjust.Source
Steady state: The point where the amount of drug going in each week equals the amount being cleared. For semaglutide that takes about four to five weeks at a given dose, which is why side effects and appetite effects keep shifting early on.Source
Step therapy: A rule that you must try (and fail on) a cheaper drug before the plan will cover the one your prescriber wants.Source
Step therapy override: The process for skipping a step-therapy requirement. Most states require insurers to grant one when the required drug is contraindicated, is expected to harm you, is unlikely to work for you, was already tried and failed, or is one you are already stable on.Source
Step-down dosing: Dropping to a lower dose once you have reached your weight goal, instead of staying on the full dose. It was tested head to head against staying put for the first time in 2026.Source
Subcutaneous injection: An injection into the fat layer just under the skin — abdomen, thigh or upper arm — rather than into a muscle or vein. All GLP-1 pens are subcutaneous.Source
SURMOUNT: Eli Lilly's phase 3 trial program for tirzepatide in obesity — SURMOUNT-1 through SURMOUNT-5 plus the sleep apnea, maintenance and cardiovascular outcome studies. If a trial name starts with SURMOUNT, it is about weight, not diabetes.Source
SURPASS: Eli Lilly's phase 3 trial program for tirzepatide in type 2 diabetes — SURPASS-1 through SURPASS-6, the regional and switch studies, the pediatric study and SURPASS-CVOT. If a trial name starts with SURPASS, it is about blood sugar, not weight.Source
Sympathomimetic amine: A stimulant-like drug that mimics adrenaline signals and blunts appetite. Phentermine is the best-known weight-loss example; the class is why these drugs raise heart rate and blood pressure.Source

T

Tachyphylaxis: When a drug effect fades with repeated dosing. The open question for tirzepatide and semaglutide is whether the slowing of stomach emptying fades over months of weekly use. Lilly's data say it does; a 2023 anesthesiology correspondence and a scintigraphy meta-analysis say it does not.Source
Tainted supplement: A product sold as a supplement that actually contains an undeclared prescription drug, often a withdrawn one such as sibutramine. The FDA maintains a public database of the products it has found.Source
Target trial emulation: A method for analyzing existing health records as though they were a randomized trial, by specifying the trial you would have run and then mimicking it. Stronger than a plain retrospective cohort, still not randomized, and still open to confounding.Source
Telehealth: Getting a prescription through an online platform rather than an in-person visit. It is how a large share of US GLP-1 prescriptions now start, and the FDA has published specific rules about how these companies may advertise.Source
Tentative approval: FDA sign-off on a generic that still cannot be sold because patents or exclusivity have not expired. Apotex holds one for generic semaglutide in the US; nothing can be marketed until the patents lapse.Source
Tiering exception: A request asking the plan to charge you the cost share of a cheaper tier for a drug that sits on an expensive one. Some plans, including the federal employee program for GLP-1s, refuse tiering exceptions outright.Source
Tirzepatide: The active ingredient in Mounjaro and Zepbound, made by Eli Lilly. It works on two receptors (GIP and GLP-1) rather than one, and beat semaglutide in the only head-to-head weight-loss trial.Source
Titration: Starting low and stepping the dose up on a schedule. Every semaglutide label does this to limit nausea and other stomach side effects, not because the low doses are the target.Source
Topline results: The company press release version of a trial result: headline numbers, no detail, no peer review. It usually arrives six to twelve months before the actual paper.Source
Triple agonist: A peptide that activates three receptors — GLP-1, GIP and glucagon. Retatrutide is the furthest along; it is not approved anywhere and its head-to-head trial against tirzepatide has not reported.Source
TrumpRx: The federal website launched in February 2026 that lists discounted direct-to-consumer prices for drugs covered by the pricing deals, including semaglutide products.Source
Type 2 diabetes: A condition where the body stops responding properly to insulin and blood sugar runs high. It is the original approved use for Ozempic, Rybelsus and Mounjaro.Source

U

U-100 syringe: The standard insulin syringe, whose 'unit' marks measure volume (100 units = 1 mL), not milligrams of drug. Reading a GLP-1 dose off those marks as if they were milligrams is how tenfold overdoses happen.Source
Unit (syringe unit): A volume mark on an insulin syringe, equal to one hundredth of a milliliter. How much drug a unit contains depends entirely on the concentration of the vial, which is why 'take 20 units' means nothing without the concentration.Source
Untitled letter: A milder FDA enforcement letter than a warning letter, often used for advertising problems — as with the February 2026 letter about a Wegovy pill TV ad.Source

W

WAC: The manufacturer's published sticker price before any rebate or discount. Almost nobody pays it, but it is the number in headlines and the base for many out-of-pocket calculations. Novo Nordisk has said semaglutide's WAC drops to $675 a month on January 1, 2027.Source
Warning letter: An FDA letter telling a company it is breaking the law and must fix it. Three waves of them hit GLP-1 compounders and telehealth marketers between September 2025 and June 2026.Source
Warnings and precautions: The label section listing the serious risks a prescriber is meant to watch for — pancreatitis, gallbladder disease, kidney injury from dehydration, diabetic retinopathy complications, severe stomach reactions and low blood sugar with other diabetes drugs.Source
Wegovy: The once-weekly semaglutide injection approved for chronic weight management, plus heart-risk reduction in people with obesity and liver disease (MASH). Same molecule as Ozempic, higher dose, different label.Source
Wegovy HD: The 7.2 mg high-dose Wegovy injection approved in March 2026 for people who need more than the standard 2.4 mg maintenance dose.Source
Wegovy tablets: Oral semaglutide 25 mg, the first GLP-1 pill approved for weight loss, cleared in December 2025 and launched in January 2026. A completely different oral product from Ozempic tablets.Source
Weight regain: What happens after stopping. Trial extensions showed about two-thirds of lost weight returning within a year; real-world cohorts show much smaller changes, largely because many people restart the drug or switch to another one.Source
Weight-loss plateau: The point where the scale stops moving on a steady dose, because the body's energy needs have fallen to match the smaller intake. In the pivotal trials it typically arrives somewhere between month 9 and month 18.Source

Y

YMYL: Google's label for topics that can affect health, safety or finances. Pages about prescription drugs are held to a higher standard of expertise and accuracy in search rankings.Source

Z

Zepbound: Eli Lilly's tirzepatide injection for chronic weight management, and the first drug ever approved for obstructive sleep apnea.Source