What Are GLP-1 Medications? How They Work and Which Ones Exist

GLP-1 (glucagon-like peptide-1) is a hormone your gut releases when you eat. It helps the pancreas release insulin when blood sugar rises, slows the passage of food from the stomach into the intestine and turns down appetite. The “GLP-1s” people talk about are medications that mimic this hormone or switch on its receptor. In the US, the FDA has approved semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound), liraglutide (Victoza, Saxenda), dulaglutide (Trulicity), exenatide (Byetta, the first one, now discontinued) and orforglipron (Foundayo). Tirzepatide also acts on a second gut hormone, GIP.

I built this guide from two reviews of the hormone, by Müller and colleagues (2019) and Drucker (2018), each drug’s FDA label and approval record, the EU prescribing information and the trials I cite. Label facts have a dotted underline and the date I checked them. Each active ingredient has a reference page in our drug section (in Spanish).

The GLP-1 hormone: where it’s made and what it does

GLP-1 is made mainly by L cells in the lining of the gut, which are most abundant toward the end of the small intestine (the ileum) and in the colon. A small group of neurons in the brainstem makes it too, according to Müller’s review. L cells release it into the blood when nutrients reach the intestine.

Once in circulation, GLP-1 does four main things, as Drucker summarizes:

• Raises insulin from the pancreas, but only when blood sugar is high. This is called a glucose-dependent effect.
• Lowers glucagon, the hormone that tells the liver to release glucose.
• Slows stomach emptying, so food stays in the stomach longer.
• Reduces food intake, partly by acting on appetite centers in the brain.

The result is that blood sugar rises less after meals and people eat less. GLP-1 is one of the incretins: gut hormones that explain why glucose taken by mouth triggers more insulin than the same glucose given into a vein. The other key incretin is GIP (glucose-dependent insulinotropic polypeptide), which comes back with tirzepatide.

Because the insulin effect depends on glucose, there’s a practical consequence. The US labels flag low blood sugar (hypoglycemia) mainly when these drugs are used with insulin or an insulin secretagogue, such as a sulfonylurea, another type of diabetes medication.

From hormone to medication

The natural hormone is nearly useless as a drug because it doesn’t last. An enzyme in the blood and tissues, DPP-4, cuts it up almost immediately, and the kidneys clear the rest. Its half-life (the time it takes the body to clear half of it) is 1 to 2 minutes in Müller’s review and 1.5 to 2 minutes in the US Victoza label.

The Gila monster

In 1992, Eng and colleagues isolated a peptide they called exendin-4 from the venom of the Gila monster (Heloderma suspectum), a venomous lizard. It resembles human GLP-1, sharing about 53% of its first 30 amino acids, and it activates the same receptor, according to Müller’s review.

Its synthetic version, exenatide (Byetta), injected twice a day, was the first drug in this family. The FDA approved it on April 28, 2005, and the EU authorized it on November 20, 2006, both for type 2 diabetes. Drugs@FDA now lists both Byetta pens as discontinued in the US; the EU still lists it as authorized.

How the effect was stretched out

Since then, each generation has aimed to last longer, so people need fewer doses:

Active ingredient	How its effect is extended	Half-life in the US label
Natural GLP-1 (Victoza label)	It isn’t: DPP-4 breaks it down	1.5 to 2 minutes
Exenatide	A lizard peptide, cleared mainly by the kidneys	2.4 hours (injected twice a day)
Liraglutide	A fatty-acid chain; binds to blood proteins and resists DPP-4	About 13 hours (once a day)
Orforglipron	A small molecule, not a peptide	About 29 to 49 hours (one pill a day)
Dulaglutide	Two copies of a GLP-1 analog fused to an antibody fragment, modified to resist DPP-4	About 5 days (once a week)
Tirzepatide	A fatty-acid chain that lets it bind to albumin, a blood protein	About 5 days (once a week)
Semaglutide	Binding to albumin is the main mechanism	About 1 week (a weekly shot or a daily pill)

Source: each drug’s US label (linked), sections 11, 12.1 and 12.3.

That’s why semaglutide and liraglutide are called GLP-1 analogs: tweaked versions of the human hormone. According to their US labels, semaglutide shares 94% of its sequence with human GLP-1, and liraglutide 97%. All of them are also GLP-1 receptor agonists: they bind to that receptor and switch it on, as the hormone does. Orforglipron activates the receptor without resembling the hormone. It’s a small molecule, not a peptide, and it’s taken by mouth.

Which GLP-1 medications exist

The table covers the approved drugs and the two furthest along in development, checked against Drugs@FDA, the FDA labels and the European Medicines Agency (EMA). Years are each brand’s first approval in that region.

Active ingredient	US brands	Type	How it’s taken	FDA approval (US)	EU authorization	Approved in the US for
Semaglutide	Ozempic (injection and tablets), Rybelsus, Wegovy (injection and tablets)	GLP-1 receptor agonist	Weekly injection (Ozempic, Wegovy); daily tablet (Rybelsus, Ozempic tablets, Wegovy tablets)	Ozempic 2017; Rybelsus 2019; Wegovy 2021; Wegovy tablets 2025; Ozempic tablets 2026	Ozempic 2018; Rybelsus 2020; Wegovy 2022; Wegovy tablets 2026	Type 2 diabetes (Ozempic, Rybelsus); weight management (Wegovy); also heart, kidney and liver uses (see below)
Tirzepatide	Mounjaro, Zepbound	Dual GIP and GLP-1 receptor agonist	Weekly injection	Mounjaro 2022; Zepbound 2023	Mounjaro 2022 (diabetes); weight management added in December 2023	Type 2 diabetes (Mounjaro); weight management and sleep apnea (Zepbound)
Liraglutide	Victoza, Saxenda, plus generics	GLP-1 receptor agonist	Daily injection	Victoza 2010; Saxenda 2014	Victoza 2009; Saxenda 2015	Type 2 diabetes (Victoza); weight management (Saxenda)
Dulaglutide	Trulicity	GLP-1 receptor agonist	Weekly injection	2014	2014	Type 2 diabetes only
Orforglipron	Foundayo	Non-peptide GLP-1 receptor agonist	Daily tablet	2026 (weight management); type 2 diabetes under review	Under EMA review	Weight management
Exenatide	Byetta	GLP-1 receptor agonist	Twice-daily injection	2005; brand now discontinued	2006	Type 2 diabetes
Cagrilintide and semaglutide	CagriSema (working name)	An amylin analog combined with a GLP-1 receptor agonist	Weekly injection (in trials)	In development: application submitted to the FDA in December 2025	In development: not on the EMA’s list of applications under review (September 2026)	Nothing approved
Retatrutide	No brand	Triple GIP, GLP-1 and glucagon receptor agonist	Weekly injection (in trials)	In development (phase 3); application planned for 2027, per the manufacturer	In development (phase 3)	Nothing approved

Sources: Drugs@FDA and the EU prescribing information (linked in the table); the EMA’s list of applications under review (September 2026); announcements from Novo Nordisk and Eli Lilly for the drugs in development and Foundayo’s diabetes application.

A few details the table can’t hold:

• Ozempic tablets. In January 2026, the FDA approved a newer semaglutide tablet under the Rybelsus application, sold as Ozempic tablets. They share one label with Rybelsus, which warns that the two are not substitutable on a mg-to-mg basis.
• Wegovy 7.2 mg. On March 19, 2026, the FDA approved a higher weekly dose, sold as Wegovy HD. The label reserves it for adults who tolerate 2.4 mg for at least 4 weeks and for whom additional weight reduction is clinically indicated. The EU prescribing information includes a 7.2 mg dose too.
• Generics. The FDA approved the first generics of exenatide and Victoza in late 2024, and Drugs@FDA lists generics of Saxenda too.
• Orforglipron elsewhere. The UK’s medicines regulator (MHRA) authorized it on August 10, 2026, for weight management and type 2 diabetes.

GLP-1, dual and triple agonists: how they differ

They all share the same base: they activate the GLP-1 receptor. What changes is whether they activate other receptors too.

GLP-1 receptor agonists (exenatide, liraglutide, dulaglutide, semaglutide, orforglipron). They act on that receptor only. This is the family with the longest track record.

Dual GIP/GLP-1 agonists (tirzepatide). They activate the GLP-1 receptor and the receptor for GIP, the other incretin. Both hormones stimulate insulin when blood sugar is high.

Triple GIP/GLP-1/glucagon agonists (retatrutide, in development). These add the glucagon receptor. That sounds contradictory, since glucagon raises blood sugar. The idea, according to Müller’s review, is to harness other effects of glucagon, such as higher energy expenditure and less liver fat, while GLP-1 offsets its effect on glucose.

Amylin combinations (CagriSema, in development). This isn’t one molecule but two: semaglutide plus cagrilintide, an amylin analog. Amylin is another hormone, released by the pancreas along with insulin, that reinforces fullness through a different pathway.

What the trials show on weight

These are the main placebo-controlled trials for each type.

Drug and type	Trial	Who took part	Length	Average weight change: drug vs. placebo
Liraglutide 3 mg daily (GLP-1)	SCALE	3,731 adults with obesity or overweight, without type 2 diabetes	56 weeks	−8.4 kg (18.5 lb) vs. −2.8 kg (6.2 lb)
Semaglutide 2.4 mg weekly (GLP-1)	STEP 1	1,961 adults with obesity or overweight, without diabetes	68 weeks	−14.9% vs. −2.4%
Semaglutide 2.4 mg weekly (GLP-1)	STEP 2	1,210 adults with overweight or obesity and type 2 diabetes	68 weeks	−9.6% vs. −3.4%
Orforglipron daily pill (GLP-1)	ATTAIN-1	3,127 adults with obesity or overweight, without diabetes	72 weeks	−7.5% to −11.2% by dose, vs. −2.1%
Tirzepatide 5 to 15 mg weekly (dual)	SURMOUNT-1	2,539 adults with obesity or overweight, without diabetes	72 weeks	−15.0% to −20.9% by dose, vs. −3.1%
Tirzepatide 10 and 15 mg weekly (dual)	SURMOUNT-2	938 adults with obesity and type 2 diabetes	72 weeks	−12.8% to −14.7%, vs. −3.2%
CagriSema weekly (combination, in development)	REDEFINE 1	3,417 adults with obesity or overweight, without diabetes	68 weeks	−20.4% vs. −3.0%
Retatrutide 1 to 12 mg weekly (triple, in development)	Phase 2	338 adults with obesity or overweight, without diabetes	48 weeks	−8.7% to −24.2% by dose, vs. −2.1%

These are averages, with a lot of variation between people, and the rows can’t be compared with each other: population, length and design all differ. SCALE reports weight loss in kilograms, and the retatrutide trial is a small phase 2 study. People with type 2 diabetes lose less, as STEP 1 vs. STEP 2 and SURMOUNT-1 vs. SURMOUNT-2 show. The manufacturers funded all of them: Novo Nordisk the SCALE, STEP and REDEFINE trials, Eli Lilly the SURMOUNT trials, ATTAIN-1 and the retatrutide trial. Retatrutide’s phase 3 obesity results have only been announced in press releases, not published in a peer-reviewed journal, so I leave them out. Its first published phase 3 trial, TRANSCEND-T2D-1, is in type 2 diabetes.

Head-to-head: tirzepatide vs. semaglutide

Two published trials have compared them directly:

• SURMOUNT-5, in 751 adults with obesity or overweight without diabetes, over 72 weeks. Weight fell 20.2% on tirzepatide and 13.7% on semaglutide, each at the maximum tolerated dose: a difference of 6.5 percentage points. It was open-label (participants knew which drug they got) and funded by Eli Lilly, which makes tirzepatide.
• SURPASS-2, in 1,879 adults with type 2 diabetes taking metformin, over 40 weeks. HbA1c (average blood sugar over the past few months) fell 2.01 to 2.30 points on tirzepatide vs. 1.86 on semaglutide 1 mg. Tirzepatide also took off 1.9 to 5.5 kg (4 to 12 lb) more. The comparison was against semaglutide 1 mg, not the higher doses approved later.

Without a trial that compares two drugs directly, any “this one beats that one” claim mixes studies that can’t be compared.

What they’re approved for

A drug is approved only for what its label says. Here’s the picture by use, US first:

Use	United States (FDA label)	European Union (EU prescribing information)
Type 2 diabetes	Ozempic (injection and tablets), Rybelsus, Mounjaro, Victoza, Trulicity, Byetta	Ozempic, Rybelsus, Mounjaro, Victoza, Trulicity, Byetta
Type 2 diabetes in children 10 and older	Mounjaro, Victoza, Trulicity	Mounjaro, Victoza, Trulicity
Weight management in adults	Wegovy (injection and tablets), Zepbound, Saxenda, Foundayo	Wegovy, Mounjaro, Saxenda
Weight management in teens 12 and older	Wegovy injection; Saxenda (over 60 kg, or 132 lb)	Wegovy and Saxenda (over 60 kg)
Lowering heart attack, stroke and cardiovascular death risk	Wegovy (injection and tablets), in adults with cardiovascular disease and obesity or overweight; in type 2 diabetes, Ozempic, Rybelsus, Ozempic tablets, Mounjaro, Victoza and Trulicity	Not a separate indication: results appear in section 5.1
Chronic kidney disease with type 2 diabetes	Ozempic injection	Not a separate indication (Ozempic, section 5.1)
Obstructive sleep apnea	Zepbound, in adults with obesity (since December 2024)	Not a separate indication (Mounjaro, section 5.1)
MASH (fatty liver disease with inflammation)	Wegovy injection (accelerated approval)	Not in the indications of the EU Wegovy label

Sources: section 1 of the US labels for Wegovy, Ozempic, Rybelsus and Ozempic tablets, Mounjaro, Zepbound, Saxenda, Victoza, Trulicity, Foundayo and Byetta; sections 4.1 and 5.1 of the EU prescribing information linked above.

Who the weight-management labels cover. The US labels name adults with obesity, or adults with overweight and at least one weight-related condition, always alongside a reduced-calorie diet and more physical activity. The EU labels spell out the numbers: a body mass index (BMI) of 30 or more, or 27 to 30 with at least one weight-related condition, such as high blood pressure or prediabetes.

Heart risk. In the SELECT trial, 17,604 adults aged 45 or older with existing cardiovascular disease, a BMI of 27 or more and no diabetes were followed for an average of 39.8 months. Heart attack, stroke or cardiovascular death occurred in 6.5% on semaglutide 2.4 mg and 8.0% on placebo. Based on this, the US Wegovy label includes reducing the risk of major adverse cardiovascular events in adults with established cardiovascular disease and either obesity or overweight.

MASH. Wegovy’s liver indication covers MASH without cirrhosis and with moderate to advanced fibrosis (stages F2 to F3) in adults. It’s an accelerated approval: it may depend on a confirmatory trial showing clinical benefit.

Everything else is off-label use or research. For example, in a phase 2 trial of 48 adults with alcohol use disorder, 9 weeks of semaglutide reduced cravings. That’s early evidence, not an approved use.

How they’re taken

There are three ways:

• Weekly injection under the skin: Ozempic, Wegovy, Mounjaro, Zepbound and Trulicity.
• Daily injection: Victoza, Saxenda and generic liraglutide.
• Daily tablet: Rybelsus, Ozempic tablets and Wegovy tablets, which are semaglutide, and Foundayo, which is orforglipron.

Semaglutide tablets come with specific instructions, because they affect how much drug is absorbed. According to the US labels for Wegovy and Rybelsus and Ozempic tablets, they’re taken once a day on an empty stomach in the morning, swallowed whole with up to 4 ounces of water and no other liquid, followed by a wait of at least 30 minutes before eating, drinking or taking other oral medications. The EU Rybelsus label adds a recommended fast of at least 8 hours beforehand. Orforglipron doesn’t have these restrictions: the Foundayo label says it’s taken once daily, with or without food.

Almost every label starts with a low dose that’s stepped up over weeks or months. The Wegovy, Zepbound and Foundayo labels give the reason: to reduce the risk of gastrointestinal adverse reactions. Which drug, which dose and how fast to step up depends on your medical history, and your prescriber decides the schedule. That’s why this guide doesn’t give one.

Side effects, in brief

The most common side effects across the family are digestive. On Wegovy 2.4 mg, the US label reports nausea in 44% vs. 16% on placebo, and diarrhea in 30% vs. 16%. On Zepbound, nausea in 25% to 29% depending on the dose vs. 8% on placebo, and diarrhea in 19% to 23% vs. 8%. I cover food strategies in GLP-1 nausea and what to eat and constipation on GLP-1 medications.

Every US label in this guide except Byetta’s carries a boxed warning, the FDA’s most prominent type. For Wegovy, it says that in rodents, semaglutide caused thyroid C-cell tumors; it’s unknown whether it does in humans, and it’s contraindicated (must not be used) in people with a personal or family history of medullary thyroid carcinoma or with MEN 2, a rare inherited condition. The others say the same for their own drug. Each medication’s full warnings are on its page in our drug section (in Spanish). For changes to the face, skin and hair that come with large weight loss, see Ozempic face.

What GLP-1 medications are not

They’re not fat burners. The US Wegovy label says that semaglutide decreases calorie intake, and the effect is likely mediated by appetite. People lose weight because they eat less. With less food, it gets harder to eat enough protein and keep muscle. I explain how in protein and muscle on GLP-1 medications, and you can estimate your target with the protein calculator (in Spanish; it works in kilograms, so divide pounds by 2.2).

They’re not for everyone. Each label defines who the drug is for and who shouldn’t use it. In the US, Ozempic, Rybelsus, Mounjaro, Victoza and Trulicity are approved only for uses tied to type 2 diabetes.

Compounded versions are not FDA-approved. The FDA explains that it doesn’t review compounded drugs for safety, effectiveness or quality before they’re sold. As of May 31, 2026, it had received 990 adverse event reports for compounded semaglutide and more than 730 for compounded tirzepatide, some linked to dosing errors and some requiring hospitalization. It considers them likely underreported, since state-licensed pharmacies that aren’t outsourcing facilities don’t have to report them. Retatrutide and cagrilintide can’t be used in compounding under federal law.

“Natural GLP-1” supplements are not GLP-1 medications. Supplements, drops or patches marketed that way haven’t been approved or evaluated for safety and effectiveness. In December 2024, the FDA sent a warning letter to a company selling weight-loss drops promoted with “The Science of GLP-1” and an “FDA APPROVED” badge. The agency found they were unapproved new drugs with false or misleading labeling. The same FDA page warns about fraudulent products labeled as compounded semaglutide or tirzepatide, some naming pharmacies that don’t exist.

Frequently asked questions

Is Ozempic a GLP-1?

Yes. Ozempic is semaglutide, a GLP-1 analog that switches on the GLP-1 receptor. In the US, it’s approved for adults with type 2 diabetes, including to lower heart and kidney risk in some of them. Wegovy is the same molecule at different doses, approved for weight management; Rybelsus and Ozempic tablets are the pill versions for diabetes.

Is Ozempic approved for weight loss?

No. Its US label covers only uses tied to type 2 diabetes. The semaglutide approved for weight management is Wegovy, as a weekly injection (since 2021) or a daily tablet (since December 2025). Using Ozempic for weight loss is off-label: outside what the FDA reviewed for that product. Which drug fits you is a question for your prescriber.

Is Mounjaro or Zepbound a GLP-1?

Partly. Tirzepatide, the drug in both, activates the GLP-1 receptor and the GIP receptor, which is why it’s called a dual agonist. In everyday speech it’s lumped in with “the GLP-1s”, and it shares their main effects and most of their warnings. Mounjaro is the brand for type 2 diabetes and Zepbound the one for weight management and sleep apnea.

Which GLP-1 is the strongest?

Among approved drugs, the largest average weight losses in people without diabetes are with tirzepatide and semaglutide 2.4 mg (see the trial table). The head-to-head trial in obesity, SURMOUNT-5, found 20.2% with tirzepatide vs. 13.7% with semaglutide. But “strongest” doesn’t mean “best for you”: tolerance, your other health conditions and the approved use all matter, and that’s for your appointment.

Are there GLP-1 pills?

Yes. In the US: Rybelsus and Ozempic tablets (semaglutide) for type 2 diabetes; Wegovy tablets (semaglutide) for weight management, approved December 22, 2025; and Foundayo (orforglipron) for weight management, approved April 1, 2026. In the EU, Rybelsus and Wegovy tablets are authorized, and orforglipron is under review.

What’s the difference between a GLP-1 agonist, a GLP-1 analog and a “GLP-1 drug”?

A GLP-1 receptor agonist is any drug that switches on that receptor. A GLP-1 analog is an agonist that also resembles the hormone, like semaglutide or liraglutide; orforglipron is an agonist but not an analog. GLP-1 drug is the everyday term, which usually includes tirzepatide.

Do they work for type 1 diabetes?

They aren’t approved for it: none of the US or EU labels I reviewed lists it as an indication. The US Wegovy label notes that use in patients with type 1 diabetes has not been evaluated, and the EU Trulicity label says dulaglutide should not be used in patients with type 1 diabetes. If you have type 1 diabetes, take any questions about these drugs to your endocrinologist.

What happens if you stop taking them?

Appetite comes back and, on average, much of the weight does too. In the STEP 1 extension, a year after stopping semaglutide and the lifestyle program, participants had regained about two-thirds of the weight they’d lost. Stopping is a decision to make with your prescriber. More in what happens when you stop Ozempic, Wegovy or Zepbound.

Do I need to change what I eat?

It helps a lot. With less appetite, each meal needs to deliver more: enough protein, fiber and fluids. There’s a full guide to what to eat on GLP-1 medications, plus nutrient data for each food in our food pages (in Spanish) and the protein calculator to estimate how much you need.