Written and fact-checked to our published editorial standards.Last updated 2026-07-26. Every clinical claim on this page is sourced to a named primary authority, listed at the foot of the page — see how we research, source, and correct our work.
The short answer
90 terms across drug mechanisms, brand and generic names, dosing, side effects, compounding and regulatory status, insurance, telehealth, and clinical-trial terminology — searchable below. Each definition is deliberately short and general; where a fuller, cited treatment already exists elsewhere on this site, the entry links straight to it rather than repeating figures out of context.
A traditional compounding pharmacy that prepares medication to fill an individual, patient-specific prescription, regulated primarily by state pharmacy boards rather than the FDA's manufacturing rules.
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503B outsourcing facility
Compounding & regulatory
A larger-scale compounding facility registered with the FDA that can produce compounded drugs in bulk, without an individual prescription in hand, typically used during an FDA-declared drug shortage. Once a drug comes off the shortage list, this bulk-compounding pathway generally closes.
A blood test that reflects average blood sugar over roughly the past three months, used both to diagnose diabetes and to measure how well a treatment is working.
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Adverse event
Side effects & safety
Any unwanted or unexpected medical occurrence in a patient taking a drug, whether or not it's proven to be caused by the drug. Clinical trials and FDA labels report the rate of each adverse event observed in the trial population.
A pre-filled, spring-loaded injection device designed to deliver a fixed dose with the push of a button, without the user handling a needle and syringe directly. Most branded GLP-1 medications ship this way.
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B
Beta cells
Drug classes & mechanisms
The cells within the pancreas that produce and release insulin. GLP-1 receptor agonists act partly by making beta cells more responsive to blood sugar.
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Bioequivalence
Compounding & regulatory
Evidence that a drug product delivers the same active ingredient to the body at the same rate and extent as the reference product. Compounded GLP-1 products are not required to demonstrate bioequivalence to the branded original the way an FDA-approved generic would be.
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BMI — Body mass index
General health terms
A simple ratio of weight to height, used as a screening tool for classifying underweight, healthy weight, overweight, and obesity. Most GLP-1 eligibility criteria, including the Medicare GLP-1 Bridge program, are written in terms of BMI thresholds.
The FDA's most serious drug-label warning, printed in a bordered box at the top of the prescribing information. GLP-1 receptor agonists carry a boxed warning about thyroid C-cell tumors observed in rodent studies, and are contraindicated in patients with a personal or family history of medullary thyroid carcinoma or MEN 2 syndrome.
Brand name for twice-daily injectable exenatide, one of the earliest GLP-1 receptor agonists for type 2 diabetes.
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C
Cash-pay
Insurance & cost
Paying the full price for a medication or service directly, without billing insurance. Most compounded-only GLP-1 telehealth providers operate on a cash-pay model.
The formation of gallstones, more common with rapid weight loss from any cause, including GLP-1 medications. Can lead to gallbladder inflammation requiring treatment.
Coinsurance
Insurance & cost
The percentage of a drug's cost you're responsible for, rather than a fixed copay — for example, paying 20% of the cost with insurance covering 80%.
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Comorbidity
General health terms
A separate health condition that exists alongside the primary one being treated — for example, high blood pressure or sleep apnea alongside obesity. Many GLP-1 eligibility and coverage rules key off specific weight-related comorbidities.
Compounded medication
Compounding & regulatory
A drug prepared by a pharmacy to an individual prescription, rather than manufactured by the original drug company. Compounded semaglutide and tirzepatide are not FDA-approved in their own right — the FDA doesn't review compounded formulations for safety, effectiveness, or manufacturing quality the way it does an approved drug.
A specific condition or situation in which a drug should not be used because the risk clearly outweighs any benefit — as opposed to a side effect, which is a risk that's weighed against benefit on a case-by-case basis.
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Copay
Insurance & cost
A fixed dollar amount you pay for a covered prescription, with your insurance plan covering the rest.
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D
Deductible
Insurance & cost
The amount you must pay out of pocket before your insurance plan starts covering costs. Some plans apply the full list price of a GLP-1 medication toward the deductible before any coverage kicks in.
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Discontinuation rate
Clinical trials & research
The share of patients who stop a medication within a defined period — the inverse of the persistence rate.
A trial design where neither the participants nor the researchers assessing outcomes know who received the actual drug versus the placebo, reducing bias in both self-reported and observed results.
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Drug shortage list
Compounding & regulatory
The FDA's official registry of medications in short supply. While a drug is listed, compounding pharmacies gain broader legal ability to produce copies. Semaglutide and tirzepatide were both removed from this list in 2024–2025, which is steadily narrowing the legal compounding pathway for both.
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Dual agonist
Drug classes & mechanisms
A medication that activates two different hormone receptors at once. Tirzepatide is a dual GIP/GLP-1 receptor agonist — the combined action is one reason its trial weight-loss figures ran higher than single-agonist semaglutide's in head-to-head-adjacent trial comparisons.
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Dulaglutide
Brand & generic names
The generic name for Trulicity, a weekly-injection GLP-1 receptor agonist approved for type 2 diabetes.
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E
Exenatide
Brand & generic names
One of the first GLP-1 receptor agonists brought to market, sold as Byetta (twice-daily injection) and Bydureon (weekly injection), for type 2 diabetes.
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F
FDA approval
Compounding & regulatory
The FDA's determination that a specific drug, at a specific dose and for a specific indication, has been shown safe and effective enough to market — based on the manufacturer's trial data. Approval is indication-specific: a drug approved for diabetes isn't automatically approved for weight loss.
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Formulary
Insurance & cost
The list of drugs a specific insurance plan covers, usually organized into cost tiers. Whether a GLP-1 medication is on your plan's formulary — and at what tier — is often the single biggest factor in what you'll pay.
Eli Lilly's brand name for orforglipron, the first oral non-peptide GLP-1 receptor agonist, FDA-approved for weight management in April 2026.
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G
Gastric emptying
Drug classes & mechanisms
The rate at which food moves from the stomach into the small intestine. GLP-1 medications slow this process substantially, which is the main reason food feels more filling and lasts longer — and the main mechanism behind nausea, bloating, and constipation.
A condition of severely delayed stomach emptying. GLP-1 medications intentionally slow gastric emptying as part of how they work, and in rare cases this effect has been reported as severe enough to resemble gastroparesis, particularly at higher doses.
A second incretin hormone, distinct from GLP-1, that also stimulates insulin release after eating. Tirzepatide activates both the GIP and GLP-1 receptors, which is why it's called a "dual agonist."
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GLP-1 — Glucagon-like peptide-1
Drug classes & mechanisms
A natural hormone released by the gut after eating. It signals the pancreas to release insulin, slows stomach emptying, and reduces appetite — the effects that GLP-1 receptor agonist medications imitate at higher, sustained levels than the body produces on its own.
A medication that binds to and activates the same receptor as the natural GLP-1 hormone, producing a stronger and longer-lasting version of its effects on blood sugar and appetite. Semaglutide and liraglutide are single GLP-1 receptor agonists.
A hormone that raises blood sugar by triggering the liver to release stored glucose — the functional opposite of insulin. GLP-1 medications suppress glucagon release when blood sugar is already high, which helps prevent post-meal spikes.
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H
Half-life
Dosing & administration
The time it takes for half of a drug dose to be cleared from the body. Semaglutide and tirzepatide have long half-lives (about a week), which is why they're dosed weekly rather than daily.
Tax-advantaged accounts that can be used to pay for qualified medical expenses, including GLP-1 medications and related visits when prescribed for a covered medical condition.
Hypoglycemia
Side effects & safety
Abnormally low blood sugar. GLP-1 medications carry a lower hypoglycemia risk on their own than insulin or sulfonylureas, because they only stimulate insulin release when blood sugar is elevated — but risk rises when combined with those other diabetes medications.
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I
Ileus
Side effects & safety
A temporary halt in normal intestinal movement, causing a functional bowel blockage without a physical obstruction. Listed as a rare but serious reported event on GLP-1 prescribing labels.
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Incretin
Drug classes & mechanisms
Any hormone released by the gut in response to eating that boosts insulin release. GLP-1 and GIP are the two major incretins in humans, and "incretin mimetic" is an older term for this drug class.
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Injection site rotation
Dosing & administration
Systematically changing the exact injection spot each dose, within the approved body areas, to avoid repeated trauma to the same patch of tissue (lipodystrophy) and keep absorption consistent.
The hormone that lowers blood sugar by helping cells absorb glucose from the bloodstream. GLP-1 medications increase insulin release, but only when blood sugar is elevated — a built-in safety feature that makes severe hypoglycemia less likely than with some older diabetes drugs.
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L
Lean mass loss
Side effects & safety
The loss of muscle and other non-fat tissue that occurs alongside fat loss during rapid weight loss. Trial data shows roughly a quarter of the weight lost on GLP-1 medications is lean mass — a normal response to fast weight loss generally, not unique to these drugs, and partly modifiable with protein intake and resistance exercise.
An earlier GLP-1 receptor agonist, sold as Victoza (diabetes) and Saxenda (weight management). Dosed daily by injection rather than weekly — largely superseded by semaglutide and tirzepatide for new prescriptions, but still in use.
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M
Maintenance dose
Dosing & administration
The target dose a patient continues on long-term after titration is complete, chosen based on tolerability and clinical response.
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Manufacturer savings card
Insurance & cost
A discount program offered directly by a drug manufacturer to lower what commercially insured patients pay out of pocket — generally not available to patients on Medicare or Medicaid, and not usable without existing insurance coverage for the drug.
The joint federal-state health coverage program for lower-income Americans. Coverage of GLP-1 medications for obesity specifically varies by state and has changed frequently as states add or roll back coverage.
The federal Medicare prescription-drug benefit. By statute, Part D cannot cover a drug prescribed solely for weight loss, though it can cover the same drug when prescribed for an approved indication like type 2 diabetes.
A rare thyroid cancer that arose in rodent studies of GLP-1 receptor agonists at high doses; it has not been confirmed to occur in humans taking these drugs, but out of caution, anyone with a personal or family history of MTC is excluded from treatment.
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MEN 2 syndrome — Multiple Endocrine Neoplasia type 2
Side effects & safety
A rare inherited condition that raises the risk of several endocrine cancers, including medullary thyroid carcinoma. It's one of the two conditions specifically excluded from GLP-1 treatment under the boxed warning.
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Metabolic syndrome
General health terms
A cluster of conditions — including excess abdominal fat, high blood pressure, high blood sugar, and abnormal cholesterol — that together raise the risk of heart disease and type 2 diabetes.
Mounjaro
Brand & generic names
Eli Lilly's brand name for injectable tirzepatide, FDA-approved for type 2 diabetes.
An advanced-practice registered nurse with prescribing authority, common as the primary prescriber on many telehealth GLP-1 platforms.
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O
Obesity
General health terms
A chronic condition of excess body fat, clinically defined as a BMI of 30 or higher, and the primary approved indication for Wegovy, Zepbound, Saxenda, and Foundayo.
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Off-label use
Compounding & regulatory
Prescribing an FDA-approved drug for a purpose, dose, or population outside what it's officially approved for. Legal and common in practice — Ozempic (approved for diabetes) has been widely prescribed off-label for weight loss — but it means the specific use hasn't been through the FDA's own review for that purpose.
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Orforglipron
Brand & generic names
A non-peptide, small-molecule oral GLP-1 receptor agonist sold as Foundayo — the first pill-form GLP-1 in its structural class, FDA-approved in April 2026.
The most you'll pay in a plan year for covered care, after which your insurance pays 100%. Manufacturer savings cards for GLP-1 medications typically don't count toward this cap.
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Overweight
General health terms
A BMI of 25–29.9. Weight-management GLP-1 medications are typically approved for adults who are overweight with at least one weight-related health condition, or who have obesity outright.
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Ozempic
Brand & generic names
Novo Nordisk's brand name for injectable semaglutide, FDA-approved for type 2 diabetes. Widely prescribed off-label for weight loss before Wegovy's approval, and still sometimes used that way.
Inflammation of the pancreas, a rare but serious adverse event reported with GLP-1 medications. Symptoms include severe abdominal pain, and it requires prompt medical attention.
The process by which independent experts in a field evaluate a study's methodology and conclusions before a journal publishes it. Peer-reviewed publication (e.g. in NEJM or The Lancet) carries more weight than a company press release describing the same results.
Persistence
Clinical trials & research
The proportion of patients still taking a medication at a given point after starting it. Real-world GLP-1 persistence is notably lower than trial completion rates — a large share of patients who start a GLP-1 for weight loss have stopped within a year.
A licensed clinician who practices medicine under physician supervision, including prescribing in most states, depending on scope-of-practice rules.
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Placebo
Clinical trials & research
An inactive treatment given to a comparison group in a trial, used to measure how much of an effect is attributable to the drug itself rather than to participation in the study. Even placebo groups in GLP-1 trials show some weight loss, from the diet and lifestyle counseling included in the trial protocol.
Blood sugar levels higher than normal but not yet high enough to be classified as type 2 diabetes. Not itself an approved indication for any GLP-1 medication, though it's often part of the broader clinical picture that leads to a prescription.
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Prescriber
Telehealth & care
A licensed clinician legally authorized to write prescriptions — physicians (MD/DO), nurse practitioners, and physician assistants, depending on state law and their own scope of practice.
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Primary endpoint
Clinical trials & research
The single, pre-specified main outcome a trial is designed to measure — for most GLP-1 weight-management trials, this is percent change in body weight at a set number of weeks.
Prior authorization
Insurance & cost
A requirement that your insurer approve a prescription before it will cover it, typically based on documented medical necessity. Extremely common for GLP-1 medications, especially for weight-loss indications.
A study design that randomly assigns participants to receive either the treatment or a comparison (often a placebo), which is the strongest available way to establish that a drug — rather than chance or expectation — caused an observed effect.
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REMS — Risk Evaluation and Mitigation Strategy
Compounding & regulatory
An FDA-mandated safety program required for certain higher-risk drugs, which can include special prescriber training, patient counseling requirements, or restricted distribution. Not all GLP-1 medications carry a REMS.
Retatrutide
Brand & generic names
An investigational triple GIP/GLP-1/glucagon receptor agonist from Eli Lilly, not yet FDA-approved as of 2026. Trial data has shown the largest weight-loss figures reported to date for this drug class.
Novo Nordisk's brand name for oral semaglutide, taken as a daily tablet, FDA-approved for type 2 diabetes.
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S
Sarcopenia
Side effects & safety
Age- or illness-related loss of muscle mass and strength. A concern raised about rapid GLP-1-driven weight loss, particularly in older adults, since some of the weight lost is muscle rather than fat.
The feeling of fullness that suppresses further eating. GLP-1 medications increase satiety both by slowing gastric emptying and by acting directly on appetite centers in the brain.
Novo Nordisk's brand name for injectable liraglutide, FDA-approved for chronic weight management, dosed daily.
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Semaglutide
Brand & generic names
The generic name for the GLP-1 receptor agonist sold as Ozempic (diabetes), Wegovy (weight management), and Rybelsus (oral tablet, diabetes). Dosed weekly by injection, or daily as a pill.
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Starting dose
Dosing & administration
The lowest dose used at the beginning of treatment, before titration increases it. Chosen to minimize side effects, not because it's expected to produce the medication's full effect.
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Step therapy
Insurance & cost
An insurance requirement to try and fail a cheaper treatment before the plan will cover a more expensive one. Some plans require step therapy through non-GLP-1 weight-loss treatments before approving a GLP-1 medication.
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STEP trial program
Clinical trials & research
Novo Nordisk's series of pivotal semaglutide trials (STEP 1 through STEP 8 and beyond), each testing the drug in a different population or against a different comparator. STEP 1 is the trial most often cited for Wegovy's headline weight-loss figure.
An injection given into the fatty layer just beneath the skin, rather than into muscle or a vein. All currently approved injectable GLP-1 medications are dosed this way, typically in the abdomen, thigh, or upper arm.
Eli Lilly's series of pivotal tirzepatide trials, paralleling the STEP program. SURMOUNT-1 is the trial most often cited for Zepbound's headline weight-loss figure; SURMOUNT-2 tested tirzepatide specifically in patients with type 2 diabetes.
Medical care delivered remotely, typically by video or messaging, rather than an in-person visit. Most GLP-1 prescribing outside a traditional primary-care relationship now happens through telehealth platforms.
The generic name for the dual GIP/GLP-1 receptor agonist sold as Mounjaro (diabetes) and Zepbound (weight management). Dosed weekly by injection.
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Titration
Dosing & administration
The gradual, stepwise increase of a medication's dose over weeks or months, rather than starting at the full target dose. GLP-1 medications are titrated specifically to reduce nausea and other GI side effects as the body adjusts.
A statistical approach that counts all randomized participants in the final result, including those who stopped taking the drug early — giving a more real-world picture of expected outcomes than only counting people who completed treatment as prescribed.
Triple agonist
Drug classes & mechanisms
A medication that activates three hormone receptors at once — typically GLP-1, GIP, and glucagon. Retatrutide is the leading triple agonist in trials as of 2026; it is not yet FDA-approved.
Eli Lilly's brand name for injectable dulaglutide, a weekly GLP-1 receptor agonist for type 2 diabetes.
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Type 2 diabetes
General health terms
A chronic condition in which the body doesn't use insulin effectively, leading to elevated blood sugar. The original and still primary approved indication for most GLP-1 medications, including Ozempic, Mounjaro, Trulicity, and Rybelsus.
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V
Vial
Dosing & administration
A small glass container of medication drawn up with a separate needle and syringe, rather than a pre-filled pen. Some GLP-1 products (and most compounded versions) are dispensed this way, which requires the patient to measure the dose themselves.
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Victoza
Brand & generic names
Novo Nordisk's brand name for injectable liraglutide, FDA-approved for type 2 diabetes, dosed daily.
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W
Wegovy
Brand & generic names
Novo Nordisk's brand name for injectable semaglutide at a higher maintenance dose (2.4mg), FDA-approved specifically for chronic weight management. Also available as an oral tablet.
This page is general education, not medical advice. Talk to your own healthcare provider about your situation before starting, stopping, or changing any medication.