Question 1

What is the difference between GLP-1 and GLP-3?

Accepted Answer

One of these names belongs to a hormone and the other belongs to a marketplace, and that is the whole of the difference. GLP-1 is glucagon-like peptide-1, a hormone the intestine releases, and a 2025 review names albiglutide, dulaglutide, exenatide, liraglutide, lixisenatide, orforglipron and semaglutide as medicines built to imitate it. Among the sources behind this page, no molecule carries the name GLP-3, and no hormone does either. It is a coinage used in selling rather than a class anybody publishes in. What the people typing it are nearly always reaching for is retatrutide, which a 2026 phase 3 trial calls a GIP, GLP-1, and glucagon triple hormone receptor agonist. So the comparison worth making is not between two hormones in a numbered series. It is between a molecule acting at one receptor and a molecule acting at three, and that comparison has trials behind it.

Question 2

How do the one-, two- and three-receptor molecules compare on evidence?

Accepted Answer

Compare the evidence rather than the promises, because the evidence is where these molecules genuinely separate. The GLP-1 molecules have the longest record and the widest approvals. A 2025 review reports that trials and real-world studies have confirmed the marked glucose-lowering and weight-lowering efficacy of these agents across diverse populations. The triple agonist sits a step behind that. Retatrutide reached a 40-week phase 3 trial at 48 sites in the USA, Mexico, and India, with 537 participants. That is a real trial, and it is one trial. The dual GLP-1 and glucagon molecules are earlier still. Survodutide is running a 76-week phase 3 trial, and cotadutide has reported from a phase 2b study in 247 participants. So the order on evidence runs the opposite way to the order on receptor count.

Question 3

Does GLP-3 work for weight loss?

Accepted Answer

The molecule behind the name does have weight figures, and they come from trials rather than from testimonials. A 2025 review sets the ladder out as measured in trial participants: liraglutide induced a weight loss of 6-8%, Semaglutide 2.4 mg once weekly improved weight loss to about 12-15%, while the dual GIP/GLP-1 receptor agonist tirzepatide once weekly has induced a weight loss of about 20% in obese people without diabetes. Retatrutide is the molecule above those on receptor count, and its phase 3 trial set the percentage change in bodyweight from baseline to week 40 as a key secondary endpoint. A key secondary endpoint is a planned measurement that is not the trial's main question. Read the whole ladder with one thing in mind. Each figure belongs to the molecule that was tested, at the amount that was tested, in the group that was enrolled, and none of it transfers to a vial labelled with a name that no trial among these sources has used.

Question 4

Does GLP-3 burn fat?

Accepted Answer

Burning fat and losing weight are two different measurements, and the trials behind these molecules nearly always recorded the second one. The retatrutide phase 3 trial measured the percentage change in bodyweight from baseline to week 40, and bodyweight on a scale holds water, muscle and fat together. One trial among these sources goes further than that. In the survodutide phase 3 programme, a subset of participants will be assessed for additional endpoints of liver fat content and body composition, which is the measurement this question is really about. That trial has published its design and its baseline characteristics rather than any result. On mechanism, a 2025 review describes how liraglutide and semaglutide have great weight loss effect through reducing food intake and delaying gastric emptying. Appetite and stomach emptying are routes to eating less, not direct evidence of fat leaving the body, and among these sources only one trial set out to measure the second thing.

Question 5

Is there a best GLP-3 for weight loss?

Accepted Answer

The question assumes a ranking exists, and the most useful thing this literature does is explain why one does not. The phase 2 retatrutide trial used dulaglutide as its active comparator, and a 2023 analysis takes that apart. Retatrutide may be superior to the GLP-1 receptor agonist dulaglutide in reducing plasma glucose and body weight, but this is not a meaningful comparison. The reason is that another GLP-1 receptor agonist (semaglutide) is more potent than dulaglutide at this and may have similar efficacy to retatrutide. In plain terms, the triple agonist was measured against a weaker member of the older class. The same analysis adds that retatrutide needs to be compared with tirzepatide as well. So the ranking readers want has not been produced, and the comparison that does exist was run against the wrong yardstick. Choosing between these molecules on published evidence is a question no trial among the sources behind this page was built to answer.

Question 6

How does retatrutide compare with tirzepatide and semaglutide?

Accepted Answer

Lining the numbers up is possible, but they come from separate trials in separate groups, which is a weaker thing than a head-to-head. On blood sugar, a 2022 review reports that an HbA1c target of less than 7.0% was attained by up to 80% with high-dose GLP-1 RAs and up to 97% with tirzepatide. The retatrutide phase 3 trial reported mean changes from baseline in HbA1c of -1.69%, -1.86% and -1.94% across its three amounts, against -0.81% with placebo in the same trial. On weight, the same 2022 review reports that a body weight loss of 10% or greater was obtained by up to 50% and up to 69% with high-dose GLP-1 RAs or tirzepatide, respectively. Those three sets of figures were produced in different trials, with different entry criteria and different durations, so setting them in a column does not turn them into a comparison. That distinction is the point of this whole section.

Question 7

Have any of these been compared head to head?

Accepted Answer

Partly, and the exceptions are worth naming precisely. The retatrutide phase 2 trial did carry an active comparator, giving participants once-weekly injections of placebo, 1.5 mg dulaglutide, or retatrutide. The cotadutide kidney study ran against a GLP-1 comparator too, giving its 247 participants one of three amounts, or 1 mg semaglutide, or placebo. Both are real comparisons. Neither is the one most readers arrive wanting. No trial among the sources behind this page put the triple agonist against tirzepatide or against semaglutide. That is the pairing that would settle the ranking question. A 2023 analysis names the gap, stating that retatrutide needs to be compared with tirzepatide. Until such a trial reports, any league table is built out of separate studies rather than measured inside one.

Question 8

What does the third receptor add?

Accepted Answer

This is the question the whole name turns on, and the literature is more careful about it than the marketing is. A 2025 review states that emerging data suggests that unimolecular GLP-1/glucagon (GCG) dual agonist, as well as GLP-1/GIP/GCG triple agonist, may offer superior weight loss efficacy over GLP-1 agonist. Notice the words emerging and may, which are carrying real weight in that sentence. A 2023 analysis is blunter, stating that the role of stimulating glucagon receptors in type 2 diabetes and obesity is poorly defined and needs to be clarified. Glucagon is the hormone that raises blood sugar, which is the opposite of what a diabetes medicine is usually for, and that is exactly why its contribution has been hard to pin down. The same analysis adds that the safety of retatrutide needs to be determined in larger and longer trials. So the third receptor is the reason these molecules exist, and it is also the least settled thing about them.

Question 9

What did these molecules do to blood pressure and cholesterol?

Accepted Answer

This is the part of the record carrying the most precise numbers. A 2026 meta-analysis of randomized trials in patients reports that retatrutide significantly decreases systolic blood pressure, by a weighted mean difference of -6.79 mmHg. Diastolic blood pressure fell by a similar measure in the same analysis. It also reports a significant reduction in the levels of total cholesterol, LDL-C, and triglycerides. One number did not move: this triple hormone receptor agonist had no significant effect on HDL-C concentrations. A separate post hoc analysis reports that survodutide, a glucagon receptor and GLP-1 receptor dual agonist, improves blood pressure in adults with obesity. A post hoc analysis is one carried out after a trial has finished rather than planned in advance, and that is a real difference in the weight it carries. Both findings belong to the molecule that was given and to the participants who received it.

Question 10

How do the adverse effects compare across these molecules?

Accepted Answer

The documented picture is consistent across the class, and that consistency is itself a finding. A 2025 review reports that the adverse events with the GLP-1-based therapies are primarily gastrointestinal and include nausea, vomiting, obstipation, or diarrhea. Obstipation means severe constipation. A 2022 review attaches a frequency and a timing, recording that gut side effects of high-dose GLP-1 RAs and co-agonists occurred in 30%-70% of patients, mostly arising within the first 2 weeks of the first dose. The retatrutide phase 3 trial describes an adverse event profile consistent with molecules with GLP-1 agonist activity. That is the trial authors saying the triple agonist behaved like the class it belongs to. The rarer end is where a class-level statement stops being much comfort. A 2025 review lists more severe side effects in patients, including pancreatitis, allergic reactions, renal function disorders and possibly an increased risk of thyroid cancer. None of those figures belongs to a vial sold as GLP-3, because the counting was done in people who received a named molecule inside a trial.

Question 11

Who cannot take GLP-3?

Accepted Answer

The question cannot be answered for a name with no molecule beneath it, but it can be answered for the molecules the name stands in for, and the answer lies in who the trials let in. The retatrutide phase 3 trial recruited adults (aged ≥18 years) with type 2 diabetes that is inadequately controlled by diet and exercise alone, with an HbA1c between 7·0% and 9·5% and a BMI of at least 23 kg/m2. The phase 2 trial before it enrolled adults aged 18-75 years with type 2 diabetes and a BMI of 25-50 kg/m2. The survodutide obesity trial required a BMI of at least 35 with one obesity complication, or at least 27 with two. Read those as boundaries rather than as warnings, because anybody outside them is not somebody a trial found a problem with. They are somebody a trial never enrolled, so no result among the sources behind this page describes their situation at all.

Question 12

How long should you take GLP-3 for?

Accepted Answer

No study among the sources behind this page sets a duration for anybody, so the question is better answered with what the trials actually ran for. The retatrutide phase 3 trial ran 40 weeks. Its phase 2 predecessor measured the change in HbA1c from baseline to 24 weeks, with further measurement at 36 weeks. The survodutide obesity trial runs to week 76, and the first-in-human work on an earlier dual agonist gave daily doses over 21 or 28 days. So the published exposure runs from three weeks to roughly eighteen months. A 2025 review then raises the harder half of the question, stating that the outstanding question is maintenance of the weight loss, possibly pharmacological treatment needs to be life-long. That sentence describes an approved medicine, prescribed and monitored, and it says nothing about how long anybody might hold a vial bought under a name the trials behind this page never used.

Question 13

Where can I buy GLP-3 retatrutide?

Accepted Answer

This page names no seller, and the reason sits inside the question. A vial labelled GLP-3 carries a word that is absent from every trial covered here, so there is nothing to check its contents against. Retatrutide is a name that can be checked, because it appears in trial registrations, in phase 2 and phase 3 publications, and in a 2026 systematic review and meta-analysis of randomized controlled trials. A 2026 framework paper places it among compounds awaiting cardiovascular outcome data, which is a position in a development programme rather than a place on a shelf. What a certificate of analysis can and cannot establish for a vial is worked through at the Retatrutide sourcing page. One separation is worth making before anybody reads further. Every figure on this page belongs to material made to a filed specification and supplied for a trial, and none of it travels to a vial carrying a different name.

Question 14

How do the dual agonists compare with the triples?

Accepted Answer

The field is wider than the two names most readers know, and its middle is instructive. A 2025 review lists new incretin peptide therapies in development. It names a long-acting glucagon receptor agonist, the dual GLP-1 and glucagon agonists survodutide, pemvidutide, mazdutide and G49, and the triple agonists retatrutide and efocipegtrutide. Not one of those names carries a number, which is worth noticing on a page about a name that does. On evidence the duals are a mixed picture. A 2022 review reports that the glucose- and weight-lowering effects of the GLP-1/glucagon RA cotadutide equal those of liraglutide 1.8 mg, an older molecule rather than a newer one. Survodutide is further along, with 274 participants enrolled in its Japanese phase 3 trial. A 2026 conference report adds another triple agonist, DR10624, from a phase 2 trial in patients with severe hypertriglyceridemia. Adding receptors has produced a crowded pipeline rather than a settled hierarchy.

Molecule	Receptors	Furthest stage reported	Participants
GLP-1 molecules	One	Trials, real-world studies and wide approvals	Not stated here
Retatrutide	Three	Phase 3, 40 weeks, 48 sites	537
Survodutide	Two: GLP-1 and glucagon	Phase 3, 76 weeks, running	Not stated here
Cotadutide	Two: GLP-1 and glucagon	Phase 2b	247

GLP-3 comparisons and stacks