GLP-1 Glossary: Key Terms and Abbreviations Explained

The words around GLP-1 medicines come from four different worlds: the FDA prescribing labels, clinical trial reports, pharmacy and compounding rules, and federal pricing programs. Each world has its own vocabulary, and a single prescription can touch all of them at once. This glossary defines the terms in plain English, with the specific numbers attached to each one.

Most of the definitions below come straight from the FDA-approved labels for Ozempic, Wegovy and Rybelsus, from FDA and CMS announcements, or from published trial results. Where a figure is a label statement rather than advice, it is presented that way.

What do GLP-1 and GLP-1 receptor agonist mean?

GLP-1 stands for glucagon-like peptide-1, a natural hormone the body releases after eating ^[1]. A GLP-1 receptor agonist is a drug that mimics that hormone, and it is the drug class semaglutide belongs to [1, 5]. According to Drugs.com, semaglutide works by increasing insulin release, lowering glucagon release, delaying gastric emptying and reducing appetite ^[1].

Two related class names appear in different places. MedlinePlus calls semaglutide injection an “incretin mimetic” ^[7]. And orforglipron (brand name Foundayo) is described by the FDA as a GLP-1 receptor partial agonist taken as a once-daily tablet ^[12].

What is the difference between Ozempic, Wegovy and Rybelsus?

All three brands contain semaglutide and are made by Novo Nordisk, but each is approved for different uses ^[1]. The first FDA approval of semaglutide was granted on December 5, 2017, for the brand Ozempic ^[1].

Ozempic is approved for type 2 diabetes blood sugar control and for reducing major cardiovascular event risk in adults with type 2 diabetes and established cardiovascular disease [1, 3]. Ozempic injection is also approved to reduce the risk of sustained eGFR decline, end-stage kidney disease and cardiovascular death in adults with type 2 diabetes and chronic kidney disease [1, 3].

Wegovy is approved for weight loss and long-term weight management in adults with obesity, or overweight plus at least one weight-related condition, and for reducing major cardiovascular event risk in adults with established cardiovascular disease plus obesity or overweight ^[2]. Wegovy injection is also approved for weight loss and weight management in patients with obesity aged 12 years and older ^[2], and for noncirrhotic MASH with moderate to advanced liver fibrosis (stages F2 to F3) in adults ^[2].

Rybelsus is a tablet approved for type 2 diabetes blood sugar control and cardiovascular event risk reduction ^[1]. The Rybelsus R2 tablet formulation was rebranded as Ozempic tablets ^[1].

	Ozempic	Wegovy	Rybelsus
Active ingredient	semaglutide	semaglutide	semaglutide
Forms	weekly injection, daily tablet	weekly injection, daily tablet	daily tablet
Tablet strengths	1.5, 4, 9 mg	1.5, 4, 9, 25 mg	3, 7, 14 mg
Main approved uses	type 2 diabetes, cardiovascular risk, kidney risk (injection)	weight management (injection age 12+, tablets adults), cardiovascular risk, MASH (injection)	type 2 diabetes, cardiovascular risk

The labels state that Rybelsus and Ozempic tablets are not substitutable on a mg-to-mg basis ^[4].

What do the newer names mean — Wegovy HD, Foundayo, tirzepatide?

Wegovy HD is a 7.2 mg weekly semaglutide injection approved for weight loss and long-term maintenance in adults with obesity, or overweight with at least one weight-related condition ^[13]. It was the fourth approval under the FDA’s Commissioner’s National Priority Voucher (CNPV) pilot program, granted 54 days after filing ^[13].

Foundayo (orforglipron) was the first new molecular entity approved under the CNPV program, 50 days after filing, and unlike oral semaglutide it does not need to be taken on an empty stomach ^[12].

Tirzepatide is the active ingredient in Mounjaro ^[21]. Zepbound is listed on the federal TrumpRx pricing site ^[16]. Liraglutide was an earlier GLP-1 receptor agonist approved for weight management ^[8].

What does titration mean?

Titration, also called dosage escalation, means starting at a low dose and stepping up on a set schedule until reaching the maintenance dosage. The Wegovy injection label, for example, states that treatment starts at 0.25 mg once weekly for 4 weeks, then follows a dosage escalation schedule that steps up every 4 weeks to the maintenance dosage ^[2]. The labeled maintenance dosage for Wegovy injection is 2.4 mg once weekly ^[2], and for Wegovy tablets it is 25 mg once daily ^[2].

The Ozempic tablet label states a starting dosage of 1.5 mg once daily for days 1 to 30, and notes that this dosage is not effective for glycemic control ^[4]. A “limitations of use” section on the Wegovy label states that use with other semaglutide-containing products, or with any other GLP-1 receptor agonist, is not recommended ^[2].

What do the injection terms mean?

Subcutaneous means injected under the skin, in the abdomen, thigh or upper arm [2, 7]. Site rotation means using a different body area for each shot, and avoiding skin that is tender, red, bruised, hard, scarred or has stretch marks ^[5].

Concentration describes how much drug is in each milliliter of liquid. Ozempic pens come in 0.68, 1.34 and 2.68 mg/mL concentrations ^[3]. Ozempic pens are multi-dose, single-patient-use pens, while the Wegovy injection is a prefilled single-dose pen [3, 2]. The Ozempic label states never to share a pen between patients, even if the needle is changed ^[3].

A flow check is the step before each Ozempic pen dose where the dose counter shows a flow check symbol. Mayo Clinic’s instructions for the Ozempic prefilled pen say that if no drop of medicine appears at the needle tip, the steps can be repeated but not more than 6 times ^[5].

What do the tablet terms mean, including SNAC?

The labels for Rybelsus and Ozempic tablets state that they are taken once daily on an empty stomach in the morning with up to 4 ounces of water, with no other liquids, and that after taking the tablet a person waits at least 30 minutes before eating food, drinking beverages or taking other oral medications ^[4]. The tablets are swallowed whole and must not be split, crushed, chewed or dissolved ^[4].

SNAC stands for salcaprozate sodium, an absorption enhancer co-formulated with semaglutide in Rybelsus and Ozempic tablets ^[4]. With SNAC, absorption of semaglutide occurs mainly in the stomach ^[4].

How long does semaglutide stay in the body?

The elimination half-life of semaglutide is approximately 1 week, and the label states it will be present in the circulation for about 5 to 7 weeks after the last dose ^[2]. Washout refers to clearing the drug before a planned event; the labels state that treatment should be stopped at least 2 months before a planned pregnancy because of the long washout period [3, 4].

Because semaglutide delays gastric emptying, the labels note it may affect the absorption of other oral medicines, and they flag use with drugs that have a narrow therapeutic index or require clinical monitoring [2, 4]. For storage, the pen is refrigerated, and it can be kept at room temperature for up to 28 days before the cap is removed ^[6].

What do boxed warning, contraindication and indication mean?

An indication is the condition a drug is FDA-approved to treat. A contraindication is a situation where a drug should not be used. For semaglutide products, the listed contraindications are a personal or family history of medullary thyroid carcinoma (MTC), Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), or serious hypersensitivity to semaglutide or any excipient [2, 3].

A boxed warning is a warning the FDA requires to appear in a boxed format at the top of the label. The semaglutide boxed warning states that the drug causes thyroid C-cell tumors in rodents at clinically relevant exposures, and that human relevance has not been determined [2, 3].

The Wegovy MASH indication was granted under accelerated approval based on improvement in MASH and fibrosis, and the label states that continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial ^[2]. Postmarketing reports are adverse events reported after approval; the Ozempic label lists ileus, intestinal obstruction and acute kidney injury among them ^[3].

What do the side-effect terms mean?

Eructation is the medical word for burping, and it appears on the Wegovy list of reactions occurring at 5% or more ^[2]. Gastroparesis means the stomach is not emptying food normally; the labels state semaglutide products are not recommended in patients with severe gastroparesis [5, 3].

Pancreatitis is inflammation of the pancreas, described as severe stomach pain that can spread to the back [6, 3]. Cholelithiasis (gallstones) and cholecystitis (gallbladder inflammation) are forms of gallbladder disease flagged in the labels [6, 3]. The labels state that concomitant use with insulin or an insulin secretagogue such as a sulfonylurea may increase the risk of hypoglycemia, including severe hypoglycemia [3, 2], and acute kidney injury can result from volume depletion [3, 2]. Pulmonary aspiration means food or liquid entering the lungs during general anesthesia or deep sedation, which is why the labels instruct patients to tell providers about planned procedures [5, 2].

What are dysesthesia and NAION?

Dysesthesia means altered skin sensation, such as sensitivity, pain or burning. Reports of dysesthesia were more frequent at the 7.2 mg Wegovy HD dose than at lower doses, and the FDA is conducting further investigations regarding this reaction ^[13]. In the STEP UP T2D trial, dysesthesia occurred in 18.9% of participants on 7.2 mg, versus 4.9% on 2.4 mg and none on placebo ^[19].

NAION stands for non-arteritic anterior ischemic optic neuropathy, an eye condition that may cause loss of vision. The European Medicines Agency’s safety committee (PRAC) concluded that NAION is a very rare side effect of semaglutide, meaning it may affect up to 1 in 10,000 people taking the medicine ^[17]. PRAC also reported that large epidemiological studies in adults with type 2 diabetes suggest about a two-fold increase in risk, corresponding to about one additional case per 10,000 person-years of treatment; one person-year means one person taking the drug for one year ^[17].

What do the clinical trial terms mean?

A placebo is a dummy treatment ^[17]. MACE, the primary cardiovascular endpoint in these trials, is a composite of cardiovascular death, nonfatal heart attack (myocardial infarction) and nonfatal stroke [2, 18]. BMI (body mass index) is weight in kilograms divided by the square of height in meters ^[18].

Two trials come up often. SELECT enrolled 17,604 patients with cardiovascular disease and overweight or obesity but no diabetes; a primary endpoint event occurred in 6.5% of the semaglutide group versus 8.0% of the placebo group, a hazard ratio of 0.80 ^[18]. STEP UP T2D enrolled 512 participants for 72 weeks; mean body weight fell 13.2% on the 7.2 mg dose versus 3.9% on placebo ^[19].

What is food noise?

Food noise is an emerging concept with no firm definition, but it is generally described as persistent, intrusive thoughts about food that disrupt daily life and make healthy behaviors difficult ^[9]. It is a colloquial term, and patients taking GLP-1 receptor agonists have reported less rumination and obsessive preoccupation with food ^[8].

Researchers connect food noise to food cue reactivity, and a 2023 review in the journal Nutrients proposed the CIRO (Cue-Influencer-Reactivity-Outcome) model to frame it ^[8]. A Food Noise Questionnaire has been developed with 5 items, each scored 0 to 4 for a total out of 20, with no set cutoff for what counts as food noise ^[9].

What is a compounding pharmacy?

Compounded drugs are drugs made by a pharmacy or other compounder rather than dispensed as an FDA-approved product. Under section 503A of federal law, a state-licensed pharmacy or physician compounds a drug for an individual patient based on a prescription ^[10]. Compounded drugs are not FDA approved, meaning they do not go through FDA pre-market review for safety, effectiveness and quality ^[11].

Under section 503B, an outsourcing facility may compound with bulk drug substances only if the substance appears on the 503B bulks list or the drug is on FDA’s shortage list at the time of compounding, distribution and dispensing ^[10].

The semaglutide injection shortage that began in 2022 was declared resolved on February 21, 2025 ^[10]. In its April 1, 2026 update, FDA stated that semaglutide and tirzepatide do not appear on the 503B bulks list or on FDA’s drug shortage list ^[10]. FDA has also stated it does not intend to take action against a compounder for making a product that is essentially a copy of a commercially available drug if the compounder fills four or fewer prescriptions of it in a calendar month ^[10].

A few more compounding terms: salt forms such as semaglutide sodium and semaglutide acetate are different active ingredients from the one in the approved drugs ^[11]. Multi-dose vials of compounded sterile medication are generally recommended to be discarded within 28 days after first use ^[11].

What do the enforcement and lawsuit terms mean?

API stands for active pharmaceutical ingredient, also called a bulk drug substance. FDA’s import alert 66-80 is a “green list” alert aimed at stopping GLP-1 APIs with potential quality concerns from entering the US supply chain ^[11]. Warning letters are FDA enforcement notices; the agency has sent them to telehealth companies marketing unapproved drugs such as retatrutide, which, like cagrilintide, is barred from compounding under federal law ^[11]. FDA has also received reports of dosing errors with compounded injectable semaglutide, some requiring hospitalization ^[11].

MDL stands for multidistrict litigation, where federal lawsuits are grouped together. There are two GLP-1 MDLs, one focused on gastroparesis and one on vision loss ^[20]. Injuries claimed include gastroparesis, ileus, intestinal obstruction and NAION, and no global settlements had been announced as of September 2026 ^[20].

What do list price, net price and maximum fair price mean?

The list price, also called the wholesale acquisition cost (WAC), is the manufacturer’s published price before any discounts. For the semaglutide group (Ozempic, Rybelsus, Wegovy), the 2024 list price was $959 per 30-day supply ^[15].

The maximum fair price (MFP) is the price CMS negotiates under the Medicare Drug Price Negotiation Program. For the semaglutide group, the negotiated price is $274 per 30-day supply, 71% below the 2024 list price, effective January 1, 2027 ^[15]. The MFP is a negotiated price for the program, not a statement of what any individual patient pays. Net price is what is actually paid after insurer rebates and patient coupons, and it differs from list price ^[21].

Package	MFP per package
Ozempic 4 mg/3 mL pen (1 pen)	$276.78
Rybelsus 7 mg, 30 tablets	$276.78
Wegovy 2.4 mg/0.75 mL pens (4 pens)	$385.63

Off-label means a drug prescribed for a use it is not approved for, such as diabetes-approved drugs prescribed for weight loss ^[21].

What is the Medicare GLP-1 Bridge?

The Medicare GLP-1 Bridge is a short-term CMS demonstration running from July 1, 2026 to December 31, 2027 that provides eligible Medicare Part D beneficiaries access to certain GLP-1 drugs ^[14]. It operates outside the Part D benefit: the Part D deductible does not apply, there is no low-income subsidy for it, and the $50 copay does not count toward the beneficiary’s TrOOP costs ^[14].

A single central processor handles prior authorization, claims adjudication and payment to pharmacies for the Bridge ^[14]. Prior authorization is the step where a plan or program must approve coverage before a prescription is filled. CMS has also stated that the BALANCE Model is not launching in 2027 ^[14].

What is TrumpRx?

TrumpRx.gov is a federal website listing drug prices, including Most-Favored-Nation prices set against a global reference price ^[16]. Zepbound is among the products listed on the site ^[16].

Sources

1. Drugs.com. Semaglutide: Uses, Dosage, Side Effects, Brands. August 26, 2026.
2. US Food and Drug Administration. WEGOVY (semaglutide) injection and tablets prescribing information. 2026.
3. National Library of Medicine DailyMed. OZEMPIC (semaglutide) injection, solution.
4. US Food and Drug Administration. RYBELSUS and OZEMPIC (semaglutide) tablets prescribing information. 2026.
5. Mayo Clinic. Semaglutide (subcutaneous route) - Side effects & dosage.
6. Cleveland Clinic. Semaglutide Injection (Wegovy): How It Works & Side Effects.
7. MedlinePlus. Semaglutide Injection.
8. PubMed Central. What Is Food Noise? A Conceptual Model of Food Cue Reactivity.
9. GoodRx. Food Noise: What It Is and How to Stop It.
10. US Food and Drug Administration. FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize.
11. US Food and Drug Administration. FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight Loss.
12. US Food and Drug Administration. FDA Approves First New Molecular Entity Under National Priority Voucher Program.
13. US Food and Drug Administration. FDA Approves Fourth Product Under National Priority Voucher Program, Higher Dose Semaglutide.
14. Centers for Medicare & Medicaid Services. Medicare GLP-1 Bridge.
15. Centers for Medicare & Medicaid Services. Fact Sheet: Medicare Drug Price Negotiation Program - Negotiated Prices for Initial Price Applicability Year 2027. June 2023.
16. TrumpRx. TrumpRx medication pricing website.
17. European Medicines Agency. PRAC concludes eye condition NAION is a very rare side effect of semaglutide medicines Ozempic, Rybelsus and Wegovy.
18. PubMed. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes.
19. PubMed. Once-weekly semaglutide 7.2 mg in adults with obesity and type 2 diabetes (STEP UP T2D): a randomised, controlled, phase 3b trial.
20. Drugwatch. Ozempic Lawsuit: September 2026 Blindness and Gastroparesis Claims.
21. Peterson-KFF Health System Tracker. How do prices of drugs for weight loss in the U.S. compare to peer nations’ prices? August 17, 2023.