GLP-1 Comparison: Semaglutide vs Tirzepatide vs Liraglutide

The GLP-1 landscape right now

GLP-1 receptor agonists have gone from niche diabetes drugs to the fastest-growing drug class in pharmaceutical history. Liraglutide (Victoza) launched in 2010, semaglutide (Ozempic) followed in 2017, and once Wegovy won approval for chronic weight management in 2021, followed by tirzepatide (Mounjaro in 2022, Zepbound in 2023), the whole category shifted into mainstream obesity medicine.

The mechanism behind all of them is the same starting point. GLP-1, short for glucagon-like peptide-1, is a hormone your gut releases after you eat. It tells your brain you are full, slows down how fast your stomach empties, and helps your body use insulin better. The catch is that natural GLP-1 barely lasts two minutes in your bloodstream. Synthetic GLP-1 drugs are built to stretch that signal out for hours or, in the weekly injectables, for days.

Where these drugs really separate from each other is everything past that shared starting point: whether they hit one hormone receptor or several, whether you inject or swallow them, how often you dose, how much weight people lose in trials, what side effects show up, whether there is heart-health data behind them, and what they cost. Comparing them side by side on those specific points, rather than by reputation, is the only way to make sense of the category.

What is FDA-approved and what is still research

The current US obesity lineup is broader than the original three-way comparison. Liraglutide is approved as Saxenda, tirzepatide as Zepbound, and semaglutide as both injectable and oral Wegovy. FDA labeling now also includes the higher-dose Wegovy HD injection. In April 2026, FDA approved the non-peptide oral GLP-1 agonist orforglipron as Foundayo for chronic weight management. Rybelsus remains the diabetes brand of oral semaglutide, while Wegovy tablets carry the weight-management indication. Current product status is reflected in the FDA Wegovy label and the FDA Foundayo approval.

Retatrutide remains investigational. Lilly announced positive topline results from TRIUMPH-1 in May 2026 and from TRIUMPH-2 and TRIUMPH-3 in July 2026, but the company has not yet received FDA approval. Those announcements move the program beyond the older phase 2 snapshot, but a corporate topline release is not the same as a complete peer-reviewed paper.

Compounded versions do not go through FDA premarket review for safety, effectiveness, or quality. FDA currently advises that a compounded GLP-1 should be used only when a patient's medical need cannot be met by an available FDA-approved drug, and it recommends filling prescriptions through a state-licensed pharmacy. Registration as a 503B outsourcing facility is not the same as FDA approval of a product, so verify the pharmacy and the prescription rather than treating a COA as the only quality check.

Where the weight loss numbers come from

Every weight loss percentage tied to these drugs traces back to a specific trial, and it helps to know which one before you compare figures across drugs. Semaglutide's roughly 15 percent average loss comes from the STEP 1 trial at 68 weeks, compared to about 2 percent on placebo (PMID 33567185). Tirzepatide's up to 22.5 percent figure comes from SURMOUNT-1 at 72 weeks on the highest dose (PMID 35658024). Liraglutide's numbers trace to the earlier SCALE trial (PMID 26132939).

Retatrutide's 24.2 percent at 48 weeks remains the peer-reviewed phase 2 figure used in this table (PMID 37366315). Lilly has since reported positive phase 3 topline results from three TRIUMPH trials in 2026. Until full trial reports are available for independent review, keep the phase 2 paper and the phase 3 announcements in separate evidence buckets.

Liraglutide deserves a fuller comparison because it answers a different access and adherence question. In SCALE, once-daily liraglutide 3.0 mg produced an average 8.0 percent weight reduction at 56 weeks, versus 2.6 percent with placebo, with both groups receiving lifestyle support (PMID 26132939). That is less than the averages reported in the pivotal weekly semaglutide and tirzepatide trials, but liraglutide has a longer clinical history and a daily schedule that some people find easier to stop or adjust with a prescriber when tolerability becomes a problem.

Cardiovascular evidence now exists for both semaglutide and tirzepatide, but the trials answer different questions. SELECT found a 20 percent relative reduction in major cardiovascular events with semaglutide versus placebo among people with obesity and established cardiovascular disease who did not have diabetes (PMID 37952131). SURPASS-CVOT later found tirzepatide noninferior, but not superior, to dulaglutide for major cardiovascular events in people with type 2 diabetes and atherosclerotic cardiovascular disease. Compare the populations and control groups before treating those results as a head-to-head verdict.

Cost changes too quickly to reduce to one durable dollar figure. Compare four numbers on the same day: the insurer's expected out-of-pocket cost, the pharmacy cash price, the manufacturer's direct-pay or savings offer, and the date that offer expires. For liraglutide, include the daily supply and any separate needle cost. For weekly semaglutide or tirzepatide, confirm the exact device, strength, and 28-day supply. The cheapest advertised starting month is not necessarily the lowest sustainable annual cost.

The Side-by-Side Answer

If the narrow question is average weight loss in the pivotal obesity trials shown here, tirzepatide ranks first, semaglutide second, and liraglutide third. If the question is the longest obesity-treatment history among these three, liraglutide has the head start. For cardiovascular evidence, semaglutide has SELECT against placebo in obesity without diabetes, while tirzepatide has SURPASS-CVOT against dulaglutide in type 2 diabetes. Those are useful results, but they are not the same experiment.

Reading the comparison without overfitting to one chart

The drug with the highest number on a weight loss chart is not automatically the right pick for you. Tolerability, contraindications, how fast you can access the drug, how quickly you have to escalate the dose, and whether you can keep your protein intake up all matter just as much as the headline efficacy figure. A drug that looks slightly weaker on paper can outperform a stronger one in real life if it is simply easier to stay on long term.

Trial averages also flatten out a wide spread of individual outcomes. Some people lose far more than the reported average, some lose much less, and some stop the drug entirely because of side effects. That is exactly why it makes more sense to look at efficacy, convenience, tolerability, cardiovascular data, and cost as separate factors rather than boiling everything down into a single winner.

What to weigh before switching GLP-1 drugs

Before you move from one GLP-1 drug to another, get specific about why. A plateau, ongoing nausea, an access or supply problem, and appetite control that just isn't cutting it are four different problems, and they point toward different fixes, not necessarily a drug switch.

It is also worth separating the medication's actual effect from behavior drift. Lower protein intake, less resistance training, and missed doses can look exactly like a pharmacology problem when they are really lifestyle slippage.

Use any comparison like this one to prepare for a conversation with your prescriber, not to replace it. A chart can organize the tradeoffs, but it cannot account for your full medical history, other medications you are on, gallbladder risk, pregnancy plans, or how a diabetes treatment plan interacts with a weight management drug.

Finally, think about the off-ramp before you think about the switch. Some people are on these medications for long-term chronic disease management, others expect a defined course with an end date. That distinction changes the real comparison: muscle retention, your food environment, how often you follow up with a provider, and what happens after a dose reduction are all part of the decision even though they rarely show up in a simple drug-versus-drug table.

Emerging compounds worth knowing about

Retatrutide is the central investigational compound to watch. It activates GIP, GLP-1, and glucagon receptors, and Lilly reported positive topline phase 3 results from TRIUMPH-1, TRIUMPH-2, and TRIUMPH-3 during 2026. It remains unapproved, and products sold outside those trials are not an approved version of Lilly's drug. The current status is summarized in Lilly's retatrutide research update.

Orforglipron no longer belongs in the emerging bucket. FDA approved it as Foundayo in April 2026, making it a current non-peptide, once-daily oral GLP-1 option for weight management. That distinction matters: it should now be compared as an approved product, not described from its older phase 2 record alone.

BRP, short for body regulating peptide, is a naturally occurring 12-amino-acid peptide reported in early research to affect body weight through a pathway separate from GLP-1. It remains preclinical. Survodutide and amycretin are also development programs rather than approved options, so trial phase and regulatory status should appear beside every efficacy number.

The Short Conclusion

Among the three injectable agents at the center of this comparison, tirzepatide leads on average weight reduction in the pivotal obesity trials, semaglutide offers multiple approved forms and SELECT cardiovascular evidence, and liraglutide is the older daily injectable with lower average weight reduction but a longer treatment history. Foundayo adds a newly approved non-peptide oral option, while retatrutide remains investigational despite positive phase 3 announcements.

The practical decision is a five-part comparison: the indication on the label, contraindications, side effects you can tolerate, coverage you can keep, and a schedule you can follow. Use the table to narrow the conversation. Use a current formulary and prescriber review to finish it.

Educational content only. Not medical advice.

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