What Is GLP-1? The Hormone and the Medicines, Explained
GLP-1 is a hormone your own gut makes after a meal, and it is also the basis of a class of prescription medicines that includes Ozempic, Wegovy, Mounjaro and Zepbound. This page explains both sides of the term in plain language: what the hormone does, what the medicines are, and who they are approved for in general terms. It is education only, not medical advice.
GLP-1 starts as a hormone in your own gut
GLP-1 stands for glucagon like peptide 1. It is an incretin hormone, which means it is released from the gut when you eat and helps coordinate what happens next. When food arrives, GLP-1 signals the pancreas to release insulin in step with the rise in blood sugar, tells the pancreas to hold back glucagon, the hormone that raises blood sugar, and sends fullness signals that help a meal come to a natural end. It also plays a part in slowing how quickly the stomach empties, so nutrients are absorbed more gradually.
The natural hormone itself does not last long. The body breaks GLP-1 down within minutes, which is fine for a signal that is meant to rise and fall with each meal. That short life is also why the hormone on its own could never be a medicine. Drug researchers had to build longer lasting versions that copy its action, and those copies are the GLP-1 medicines people now talk about. The fuller mechanism, step by step, is covered on the how does GLP-1 work page.
From hormone to medicine class
The medicines are called GLP-1 receptor agonists. Agonist simply means the medicine activates the same receptor the natural hormone uses, so the body responds as if GLP-1 activity were higher and lasted far longer. Because the drug versions resist the rapid breakdown that clears the natural hormone, a single weekly injection can keep that signal present all week. Semaglutide has a half-life of about 1 week, which is why Ozempic and Wegovy are taken once a week.
That one design idea explains most of what people experience on these medicines. Appetite falls because fullness signaling is stronger and steadier. Blood sugar control improves in type 2 diabetes because insulin release is better matched to meals. The stomach empties more slowly, especially early in treatment, which is also why nausea is the most commonly discussed side effect and why doses are raised slowly. The class overview, brand by brand, is on the GLP-1 drugs and medications page.
Two ingredients, four brands
Most of the current conversation involves just two active ingredients. The first is semaglutide, sold as Ozempic for type 2 diabetes and as Wegovy for weight management, with the same ingredient also available as the daily Rybelsus tablet for type 2 diabetes. The second is tirzepatide, sold as Mounjaro for type 2 diabetes and as Zepbound for weight management and for moderate to severe obstructive sleep apnea in adults with obesity. Tirzepatide activates a second gut hormone receptor, GIP, as well as GLP-1, which is the main design difference between the two ingredients.
An older ingredient, liraglutide, is taken daily rather than weekly and belongs to the same class. Newer and investigational medicines are in development, but they are not the same as approved medicines and should not be treated as interchangeable. Keeping the names straight matters, because each brand has its own approved uses, its own dose schedule and its own label. The dosage charts on this site set out the published schedules, including the Ozempic dosage chart and the Zepbound dosage chart.
Who the medicines are approved for, in general terms
Approvals differ by brand, and the details belong on each label, but the general pattern is consistent. The diabetes brands, Ozempic, Mounjaro and Rybelsus, are approved to improve blood sugar control in adults with type 2 diabetes. Ozempic is also approved to reduce the risk of kidney disease progression in adults with type 2 diabetes and chronic kidney disease. The weight management brands, Wegovy and Zepbound, are approved for chronic weight management in adults with obesity, or with overweight plus a weight related condition. Wegovy is also approved for adolescents aged 12 and older, and for reducing cardiovascular risk in adults with cardiovascular disease and obesity or overweight. Zepbound carries the sleep apnea approval described above.
Approved for does not mean right for everyone. Every label in the class carries a boxed warning about thyroid C cell tumors and a contraindication for people with a personal or family history of medullary thyroid carcinoma or MEN 2 syndrome. Labels also advise stopping semaglutide at least 2 months before a planned pregnancy. Whether a GLP-1 medicine fits a particular person, and which brand, is a decision for that person and their prescriber. The GLP-1 BMI eligibility calculator gives a general sense of the weight criteria the labels use, and nothing more.
Why GLP-1 became such a big topic
Interest grew because the trial results were larger than people expected from a medicine. In the STEP 1 trial, semaglutide 2.4 mg produced an average loss of 14.9 percent of body weight at 68 weeks. In SURMOUNT-1, tirzepatide produced an average loss of 20.9 percent at the 15 mg dose at 72 weeks. Those figures come from separate trials and are not a head to head comparison, and individual results vary widely. What they changed was expectations: weight loss of a size previously associated mainly with surgery was being seen, on average, with a weekly injection.
With that interest came cost and access questions, because list prices are high and insurance coverage varies a great deal. The pillar page on GLP-1 cost sets out the approximate list prices and the routes people use to pay, and the page on GLP-1 weight loss looks at the results evidence and what getting started involves. Reading those two alongside this page gives the full picture: what the medicines are, what they do, and what they cost.
Terms that cause confusion
A few terms are worth pinning down. GLP-1 is the hormone. A GLP-1 medicine is a drug that activates its receptor. Brand names such as Ozempic and Mounjaro are not ingredient names, and one ingredient can sit behind several brands with different approved uses. Compounded products are pharmacy made versions that are not FDA approved, however they are marketed, and they are not generic versions of the brands, because no FDA approved generic exists for these medicines. Finally, supplements and foods may influence the body in various ways, but none of them is a GLP-1 medicine, a distinction the GLP-1 supplements and GLP-1 diet pages keep clear.
How the medicines are actually taken
Most GLP-1 medicines are once weekly injections given under the skin, on the same day each week, with the dose raised slowly over months. The weekly rhythm is possible because the drug versions were engineered to last, unlike the natural hormone. The exception in the current list is the daily Rybelsus tablet, described above, and the older daily liraglutide injections. Pens are prefilled and designed for home use after training from a clinician or pharmacist, and the injection site pages on this site explain the labeled sites in detail.
Treatment is also not usually a short course. The diabetes uses are long term by nature, and the weight management evidence was gathered over trials lasting well over a year, with regain commonly following stopping. That long horizon is worth understanding at the start, because it shapes the cost, the follow up and the commitment involved. The pages linked throughout this hub, on working, weight, cost and diet, each take one part of that picture and go deeper, so a new reader can build the full view in an order that suits their questions.
Frequently asked questions
What does GLP-1 stand for?
GLP-1 stands for glucagon like peptide 1. It is an incretin hormone released from the gut after eating. It helps the pancreas release insulin in step with blood sugar, holds back glucagon, slows stomach emptying and supports the feeling of fullness that ends a meal.
Is GLP-1 a hormone or a medicine?
Both uses of the term are correct, which is why it confuses people. GLP-1 itself is a hormone your body makes. GLP-1 medicines are prescription drugs, called receptor agonists, that copy the hormone action and last far longer than the natural hormone does.
What are the main GLP-1 medicines?
The medicines most people mean are built on two ingredients. Semaglutide sits behind Ozempic, Wegovy and the Rybelsus tablet. Tirzepatide sits behind Mounjaro and Zepbound. An older daily ingredient, liraglutide, is also in the class. Each brand has its own approved uses and schedule.
Who are GLP-1 medicines approved for?
In general terms, the diabetes brands are approved for adults with type 2 diabetes, and the weight management brands are approved for adults with obesity, or overweight with a weight related condition. Wegovy is also approved for adolescents aged 12 and older. The exact criteria are on each label, and suitability is a prescriber decision.
Are GLP-1 medicines the same as insulin?
No. Insulin is a hormone replaced directly, while GLP-1 medicines prompt the body to release its own insulin in step with meals and blood sugar. They work through a different pathway, and people with type 2 diabetes sometimes use both, under their prescriber direction.