Semaglutide vs tirzepatide: how they differ and which fits which goal

Semaglutide and tirzepatide are the two medications behind most of the weight loss people are talking about in 2026, and they are close cousins rather than the same drug. Both are once-weekly injections that act on gut hormones to reduce appetite, both come as a weight-management brand and a diabetes brand, and both require a prescription. The practical differences, how many receptors each one targets, how much weight each tends to produce, what else each is approved for, and what each costs, are what usually decide which one is right for a given person. This page lays them side by side from the FDA labels and the head-to-head trial, then explains how that maps to a goal. For the fuller picture on starting one with a provider, see our guide to GLP-1 weight-loss therapy online.

What is the main difference between semaglutide and tirzepatide?

The core difference is how many gut-hormone receptors each drug activates: semaglutide targets one (GLP-1), and tirzepatide targets two (GIP and GLP-1). That single design choice ripples through everything below, including how much weight each produces on average. Here is how the two medications compare at a glance.

The highest approved weight-management doses are semaglutide 7.2 mg, the Wegovy HD strength the FDA approved in March 2026 (its STEP UP trial reported a mean weight loss of 20.7%) (FDA, Wegovy HD approval), and tirzepatide 15 mg (Zepbound label, DailyMed). Tirzepatide’s two-receptor design is the headline structural difference, and the sections below unpack what it means for results, safety, and price in practice.

How do the mechanisms differ, GIP versus GLP-1?

Semaglutide is a GLP-1 receptor agonist, and tirzepatide is a dual GIP and GLP-1 receptor agonist, which is the central mechanistic distinction between them. Semaglutide “acts as a GLP-1 receptor agonist that selectively binds to and activates the GLP-1 receptor, the target for native GLP-1,” according to its FDA label (Wegovy Prescribing Information, DailyMed). Tirzepatide instead “selectively binds to and activates both the GIP and GLP-1 receptors,” making it the first medicine of its kind to work on two incretin pathways at once (Zepbound Prescribing Information, DailyMed). Both receptors are tied to appetite, satiety, and how the body handles calories, so both drugs reduce hunger and slow stomach emptying; adding the GIP action is the leading explanation for why tirzepatide has tended to produce more weight loss in trials, though the two are not simply interchangeable and respond differently from person to person. The same receptor logic points to what researchers are testing next: an investigational triple agonist called retatrutide adds a third receptor target on top of GIP and GLP-1. Our retatrutide vs tirzepatide comparison sets the two side by side, and The Treatment Report’s retatrutide overview covers what its trials have shown. Status: Retatrutide: Investigational; not FDA-approved. Lilly plans to submit it for approval in Q1 2027. What these status terms mean.

Which brands are which, Ozempic, Wegovy, Mounjaro, and Zepbound?

Each molecule is sold under two brand names, one approved for weight management and one for type 2 diabetes, which is the single most common source of confusion. Semaglutide is sold as Wegovy for chronic weight management and as Ozempic for type 2 diabetes, where it is indicated “to improve glycemic control in adults with type 2 diabetes mellitus” (Ozempic label, DailyMed). Tirzepatide is sold as Zepbound for weight management and as Mounjaro for type 2 diabetes, carrying the same glycemic-control indication (Mounjaro label, DailyMed). On the weight-management side, Zepbound is FDA-approved to “reduce excess body weight and maintain weight reduction long term in adults with obesity or adults with overweight in the presence of at least one weight-related comorbid condition,” and it is now also approved “to treat moderate to severe obstructive sleep apnea (OSA) in adults with obesity” (Zepbound label, DailyMed). Wegovy is FDA-approved for weight management in “adults and pediatric patients aged 12 years and older with obesity,” and it carries an additional approval to “reduce the risk of major adverse cardiovascular events (cardiovascular death, non-fatal myocardial infarction, or non-fatal stroke) in adults with established cardiovascular disease and either obesity or overweight” (Wegovy label, DailyMed). That cardiovascular indication is a meaningful point of difference: as of 2026 it belongs to semaglutide, not tirzepatide.

Which one produces more weight loss?

Tirzepatide produced more weight loss than semaglutide in the only large head-to-head trial, SURMOUNT-5. That study randomized 751 adults with obesity and without diabetes to the maximum tolerated dose of either tirzepatide (10 mg or 15 mg) or semaglutide (1.7 mg or 2.4 mg) once weekly for 72 weeks, and it measured change in body weight as the primary endpoint. Tirzepatide reduced body weight by a mean of 20.2%, versus 13.7% for semaglutide, a difference that was statistically significant (p < 0.001); waist circumference fell 18.4 cm versus 13.0 cm (SURMOUNT-5, New England Journal of Medicine 2025;393(1):26-36, via the American College of Cardiology). Each drug’s own placebo-controlled trials point the same direction. In STEP 1, 1,961 adults on semaglutide 2.4 mg lost a mean of 14.9% of body weight over 68 weeks, versus 2.4% on placebo, with 50.5% of the semaglutide group losing at least 15% (Wilding et al., STEP 1, NEJM 2021, PubMed). In SURMOUNT-1, 2,539 adults on tirzepatide lost 15.0%, 19.5%, and 20.9% at the 5 mg, 10 mg, and 15 mg doses respectively over 72 weeks, versus 3.1% on placebo, with 57% of the 15 mg group losing at least 20% (Jastreboff et al., SURMOUNT-1, NEJM 2022, PubMed). Those head-to-head numbers used semaglutide at 2.4 mg, the highest dose approved when SURMOUNT-5 ran; in March 2026 the FDA approved a higher-dose semaglutide, Wegovy HD (7.2 mg), which produced a mean 20.7% weight loss in its own STEP UP trial (FDA, Wegovy HD approval), though no head-to-head trial has yet compared Wegovy HD against tirzepatide. Averages are not individual results, though: some people lose more on semaglutide than the average person does on tirzepatide, tolerability differs, and the “better” drug is the one a person can stay on and respond to. PeptideAgent’s Wegovy vs Zepbound comparison reaches the same split verdict, favoring tirzepatide for weight loss alone and semaglutide for its broader label, including the SELECT cardiovascular result.

How do the side effects compare?

Both drugs share the same main side effects, which are gastrointestinal, and both carry the same boxed warning about thyroid C-cell tumors. On the Wegovy label the most common adverse reactions are nausea (44%), diarrhea (30%), vomiting (24%), and constipation (24%) (Wegovy label, DailyMed), while Zepbound lists nausea (25% to 29%), diarrhea (19% to 23%), constipation (11% to 17%), and vomiting (8% to 13%) (Zepbound label, DailyMed). In the SURMOUNT-5 comparison, most gastrointestinal events were mild to moderate and happened during dose escalation, and discontinuation because of them was actually lower on tirzepatide (2.7%) than on semaglutide (5.6%) (SURMOUNT-5, via ACC). Both labels warn that “in rodents, semaglutide causes thyroid C-cell tumors” and that the same is seen with tirzepatide in rats, and both drugs are contraindicated “in patients with a personal or family history of MTC,” medullary thyroid carcinoma, “or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)” (Wegovy label; Zepbound label). That shared warning is one reason both are prescription medications that call for a real clinical evaluation rather than a questionnaire alone.

What about cost and insurance?

Both medications are expensive at list price, well over $1,000 a month before insurance, though each manufacturer now runs a self-pay program that lowers the cash price substantially. Novo Nordisk lists Wegovy at $1,349.02 per package and, through its NovoCare program, offers self-pay pricing from about $299 per month for the pen for patients without coverage (NovoCare, Wegovy cost information). Eli Lilly’s published list price for Zepbound is roughly $1,086 per month, and its LillyDirect self-pay single-dose vials were lowered in late 2025 to a range of about $299 for the starting dose up to roughly $449 for higher doses (Lilly Zepbound pricing information). Which drug is cheaper for a given person depends far more on coverage than on the sticker price: insurance for weight-loss medication varies widely from plan to plan, and a plan that covers these drugs for type 2 diabetes may still exclude them for weight loss, which is why the manufacturer self-pay programs matter for people paying cash. Check your own formulary and current manufacturer pricing before assuming either number.

Is compounded semaglutide or tirzepatide a cheaper option in 2026?

Not in any way that holds up: the shortage-era supply of low-cost compounded semaglutide and tirzepatide has largely gone, and a cheap compounded vial is a different product from the ones compared on this page. The FDA determined the tirzepatide shortage resolved in 2024 and the semaglutide shortage on February 21, 2025, which ended the basis for widespread compounding (FDA, policies for compounders as GLP-1 supply stabilizes). None of the trials above tested a compounded product, compounded versions are not FDA-approved, and the FDA has received adverse event reports, some requiring hospitalization, that may be linked to dosing errors with compounded semaglutide measured from multi-dose vials (FDA, concerns with unapproved GLP-1 drugs). For a full comparison, see our guide to branded versus compounded GLP-1s. The short version for a comparison shopper: price the branded options and the manufacturer self-pay programs first.

Which one is right for you?

The better choice depends on your goal, health history, side-effect tolerance, insurance, and how your body responds, which is why it is a clinical decision rather than a fixed ranking. If the single priority is the largest average weight loss, the head-to-head evidence favors tirzepatide (Zepbound); if you have established cardiovascular disease, semaglutide (Wegovy) carries the approval to reduce cardiovascular risk; if obstructive sleep apnea is part of the picture, tirzepatide (Zepbound) is the one approved for it; and if a particular plan covers one drug and not the other, coverage may make the decision for you. Tolerability, starting dose, and how much weight you have to lose all factor in too, and the honest answer for most people is that the right first medication is the one a provider selects with them and that they can actually stay on. A prescription is never promised in advance. If you want to keep researching before a visit, our guides to what happens when you stop a GLP-1 and GLP-1 and muscle loss cover two questions that come up right after this one. If the question is deep belly fat rather than the number on the scale, tesamorelin for belly fat explains how that growth-hormone drug differs from both.

Sources

Every clinical figure on this page traces to an FDA product label or a peer-reviewed randomized trial, every price to the manufacturer’s published pricing, and every regulatory date or safety report to an FDA statement. They are listed here so you can verify each claim directly.

• Wegovy (semaglutide) Prescribing Information, DailyMed, GLP-1 mechanism of action, indications (weight management, ages 12 and older, cardiovascular risk reduction), the thyroid C-cell tumor boxed warning and contraindication, and the most common adverse reactions.
• Zepbound (tirzepatide) Prescribing Information, DailyMed, dual GIP and GLP-1 mechanism, indications (weight management and moderate-to-severe obstructive sleep apnea), the boxed warning and contraindication, adverse reactions, and the 15 mg maximum maintenance dose.
• Ozempic (semaglutide) Prescribing Information, DailyMed, the type 2 diabetes glycemic-control indication for the semaglutide diabetes brand.
• Mounjaro (tirzepatide) Prescribing Information, DailyMed, the type 2 diabetes glycemic-control indication for the tirzepatide diabetes brand.
• FDA, approval of higher-dose semaglutide (Wegovy HD, 7.2 mg), the March 2026 approval of the 7.2 mg weight-management dose and the 20.7% mean weight loss reported in the STEP UP trial.
• Aronne LJ, et al. SURMOUNT-5: tirzepatide vs semaglutide, New England Journal of Medicine 2025;393(1):26-36 (summary via the American College of Cardiology), the head-to-head 72-week weight-loss, waist-circumference, and discontinuation figures.
• Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1), NEJM 2021 (PubMed), the 14.9% semaglutide weight-loss figure and threshold responder rates.
• Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1), NEJM 2022 (PubMed), the 15.0% / 19.5% / 20.9% tirzepatide weight-loss figures by dose and threshold responder rates.
• NovoCare, Wegovy (semaglutide) cost, coverage, and savings, Wegovy list price ($1,349.02/package) and NovoCare self-pay pricing.
• Lilly, Zepbound (tirzepatide) pricing information, Zepbound list price and LillyDirect self-pay single-dose vial pricing.
• FDA, policies for compounders as national GLP-1 supply stabilizes, resolution of the semaglutide (February 21, 2025) and tirzepatide (2024) shortages.
• FDA, concerns with unapproved GLP-1 drugs used for weight loss, adverse event reports linked to dosing errors with compounded semaglutide and the multi-dose vials compounded GLP-1s are often dispensed in.