GLP-1 stands for glucagon-like peptide-1. The drug labels spell it out the long way, as in Zepbound's warning that it should not be combined "with any glucagon-like peptide-1 (GLP-1) receptor agonist".1 It is a hormone, made in the gut and released after a meal,16 and it is the reason a single class of drugs went from diabetes clinics to the most searched medicines in the country. This page explains what the hormone does, how the drugs copy it, and which GLP-1 medications are on the US market, with what each one is actually approved to treat. The prices live on every GLP-1 drug compared; this is the explainer that sits above them.
What GLP-1 stands for, and what the hormone does
Your body already makes GLP-1. A review of its physiology describes it as "a blood glucose-lowering hormone that is released from enteroendocrine L cells of the distal intestine after the ingestion of a meal."16 It is one of two "incretin" hormones whose "main physiological role" is "augmenting insulin secretion after their nutrient-induced secretion from the gut"; the other is GIP, which matters later for tirzepatide.15 Ozempic's label describes it as "a physiological hormone that has multiple actions on glucose, mediated by the GLP-1 receptors", and Wegovy's label adds the part most people care about: "GLP-1 is a physiological regulator of appetite and caloric intake, and the GLP-1 receptor is present in several areas of the brain involved in appetite regulation."23
Put together, the labels describe four things GLP-1 does after you eat:
- Raises insulin, but only when it is needed. Semaglutide "stimulates insulin secretion and lowers glucagon secretion, both in a glucose-dependent manner. Thus, when blood glucose is high, insulin secretion is stimulated, and glucagon secretion is inhibited."2 The "glucose-dependent" part is why these drugs on their own rarely cause low blood sugar.
- Lowers glucagon, the hormone that tells the liver to release sugar.
- Slows the stomach. Mounjaro's label: it "delays gastric emptying".4 Food leaves the stomach more slowly, and stomach effects such as nausea are the class's most common side effects.
- Turns down appetite in the brain, through the receptors the Wegovy label places "in several areas of the brain involved in appetite regulation".3
How GLP-1 drugs work
A GLP-1 drug is a molecule built to bind the same receptor as your own hormone. Semaglutide, the molecule in Ozempic and Wegovy, "is a GLP-1 analogue with 94% sequence homology to human GLP-1" that "selectively binds to and activates the GLP-1 receptor, the target for native GLP-1."2
The difference is how long it lasts. The drugs are engineered for staying power, and Ozempic's label explains how: "The principal mechanism of protraction resulting in the long half-life of semaglutide is albumin binding", and "semaglutide is stabilized against degradation by the DPP-4 enzyme".2 That staying power is why the injections are taken once a week and the pills once a day.
Tirzepatide, the molecule in Mounjaro and Zepbound, goes one step further. It "is a GIP receptor and GLP-1 receptor agonist" that "selectively binds to and activates both the GIP and GLP-1 receptors", GIP being the second gut incretin hormone described above.415 Its label puts the result in one sentence: it "lowers fasting and postprandial glucose concentration, decreases food intake, and reduces body weight".4 Whether hitting two receptors is why tirzepatide produced more weight loss than semaglutide in their head-to-head trial is our tirzepatide vs semaglutide guide's subject.
The newest drug in the class, Foundayo (orforglipron), is a daily pill. Its label describes the same chain in plain terms: it "binds to and activates the human GLP-1 receptor", it "decreases food intake. This effect is likely mediated by decreased appetite", and it "reduces body weight, with greater fat mass loss than lean mass loss."5
Every GLP-1 medication on the US market
Seven brands, four molecules. The approved use belongs to the brand and its label, not to the molecule: Ozempic and Wegovy are both semaglutide, but only one is labelled for weight loss. Each row below quotes or summarises the brand's own label.567891011
| Brand | Molecule | Form | FDA-approved for |
|---|---|---|---|
| Ozempic | semaglutide | weekly injection | type 2 diabetes; heart and kidney risk reduction in type 2 diabetes |
| Rybelsus and Ozempic tablets | semaglutide | daily pill | type 2 diabetes; heart risk reduction in type 2 diabetes |
| Wegovy | semaglutide | weekly injection or daily pill | weight loss and long-term maintenance; heart risk reduction; MASH liver disease (injection) |
| Mounjaro | tirzepatide | weekly injection | type 2 diabetes (adults and children 10 and up); heart risk reduction in type 2 diabetes |
| Zepbound | tirzepatide | weekly injection | weight loss and long-term maintenance; moderate to severe sleep apnea with obesity |
| Foundayo | orforglipron | daily pill | weight loss and long-term maintenance (approved 2026) |
| Trulicity | dulaglutide | weekly injection | type 2 diabetes (adults and children 10 and up); heart risk reduction in type 2 diabetes |
Two details from those labels are worth flagging. The weight-loss labels all use the same wording: for "adults with obesity or adults with overweight in the presence of at least one weight-related comorbid condition", in combination with diet and exercise.10 And the semaglutide pills are not interchangeable with each other dose for dose: "RYBELSUS and OZEMPIC tablets are not substitutable on a mg-to-mg basis."7 Older daily GLP-1 injections such as liraglutide also exist; the table covers the brands most people are comparing today.
Each of these has its own page with sourced prices and guides: Ozempic, Wegovy, Zepbound, Foundayo, Mounjaro and the GLP-1 pills.
Semaglutide vs tirzepatide vs the rest
For practical purposes, most decisions come down to two molecules. Semaglutide is the GLP-1-only drug sold as Ozempic, Rybelsus and Wegovy. Tirzepatide is the dual GIP and GLP-1 drug sold as Mounjaro and Zepbound. Dulaglutide (Trulicity), "a human GLP-1 receptor agonist with 90% amino acid sequence homology to endogenous human GLP-1", is labelled for type 2 diabetes only, where it "decreases glucagon secretion and slows gastric emptying".11 Foundayo is the first daily pill approved specifically for weight loss under its own brand, with an initial US approval in 2026.5
What comes next, GLP-2, GLP-3 and the triple-hormone drugs in trials, is in GLP-1 vs GLP-2 vs GLP-3.
Side effects the whole class shares
Because every GLP-1 drug slows the stomach, they share the same leading side effects. Wegovy's label lists the most common, at 5 percent or more: "nausea, diarrhea, vomiting, constipation, abdominal pain, dysesthesia, headache, fatigue, dyspepsia, dizziness, abdominal distension, eructation, hypoglycemia in patients with type 2 diabetes, flatulence, gastroenteritis, gastroesophageal reflux disease, and hair loss."12 On Zepbound, stomach reactions "occurred more frequently among patients receiving ZEPBOUND (5 mg 56%, 10 mg 56%, 15 mg 56%) than placebo (30%)", and most of them "occurred during dose escalation and decreased over time."13 Foundayo, a pill, still "delays gastric emptying", with the delay "largest after the first dose".5
The full, dose-by-dose numbers are drug by drug: Ozempic, Wegovy, Zepbound, Mounjaro and semaglutide in general. The practical playbook for the common ones is nausea, constipation and diarrhea on a GLP-1.
Compounded GLP-1: same molecule, not the same product
Alongside the brands there is a large market in compounded semaglutide and tirzepatide, mixed by pharmacies and sold through telehealth programs, usually for much less. The molecule is the same; the approval is not. The FDA's own wording: "unapproved versions do not undergo FDA's review for safety, effectiveness and quality before they are marketed."14 That trade, lower price against no FDA review of the finished product, is the one most buyers are weighing, and our guides to whether compounded semaglutide is safe and compounded tirzepatide lay it out with the FDA's own statements.
What GLP-1 drugs cost
Price depends on three things more than on the molecule: whether your insurance covers the brand, whether you pay the maker directly, and whether you choose a compounded program. The board below is every program we track, ranked by what actually leaves your account, membership fees included, and re-checked weekly. For insurance, start with the coverage checker; for the brand makers' own cards, see GLP-1 savings cards.
Everything on this page about how the drugs work and what they treat is quoted from their FDA labels. It is not medical advice: whether a GLP-1 is right for you, and which one, is a decision for a prescriber who knows your history.
