Wegovy vs Zepbound: The Obesity Head-to-Head, Settled by SURMOUNT-5

Two drugs got put in the same room, dosed the same way, for the same 72 weeks. Zepbound stripped off 20.2% of body weight. Wegovy managed 13.7%. That is SURMOUNT-5, the first head-to-head trial of tirzepatide against semaglutide for obesity, and it is the single number that should frame how you read every other claim about these two (Aronne et al. 2025).

That gap does not make Wegovy a bad drug. It makes Zepbound the more powerful one for total weight loss. The rest of this comparison is about the cases where "most weight lost" is not the only thing you are optimizing for, because for a lot of people it genuinely is not.

The one trial that settles most of the argument

For years the Wegovy-vs-Zepbound debate ran on cross-trial arithmetic. STEP 1 said semaglutide, SURMOUNT-1 said tirzepatide, and everyone argued about whether the two study populations were even comparable. SURMOUNT-5 ended that argument. Eli Lilly enrolled 751 adults with obesity and no diabetes, randomized them 1:1 to weekly tirzepatide or weekly semaglutide, titrated both to the maximum tolerated dose, and followed them for 72 weeks (Aronne et al. 2025).

The least-squares mean weight change came in at -20.2% for tirzepatide and -13.7% for semaglutide (P<0.001). That is a 6.5 percentage-point spread, and in relative terms tirzepatide delivered roughly 47% more weight loss than semaglutide under an identical protocol. Tirzepatide participants were also more likely to hit every threshold that matters, from at least 10% loss up through 25%, and they lost more waist circumference. Same class, same schedule, same trial, clear winner on the scale.

Wegovy vs Zepbound at a glance

What each drug actually is

Wegovy is Novo Nordisk's brand of semaglutide dosed at 2.4 mg once weekly, FDA-approved for chronic weight management in 2021. It is a GLP-1 receptor agonist: one incretin pathway, hit hard. Its diabetes-dose sibling is Ozempic, the same molecule at lower doses, which is why the Ozempic vs Wegovy question is really a dosing question, not a drug question. The full pharmacology lives on our semaglutide guide.

Zepbound is Eli Lilly's brand of tirzepatide, approved for obesity in late 2023 and titrated up to 15 mg once weekly. Tirzepatide is a dual agonist: it activates the GLP-1 receptor and the GIP receptor at the same time. That second pathway appears to add appetite and metabolic effects a GLP-1-only drug never reaches, and it is the leading explanation for the SURMOUNT-5 gap. The diabetes-dose sibling here is Mounjaro, and the Ozempic vs Mounjaro matchup mirrors this one at diabetes doses. Mechanism and half-life details sit on our tirzepatide guide.

The efficacy gap, with the numbers

Look at the pivotal monotherapy trials and the story stays consistent. In STEP 1, semaglutide 2.4 mg produced 14.9% mean weight loss at 68 weeks versus 2.4% for placebo (Wilding et al. 2021). In SURMOUNT-1, tirzepatide 15 mg produced 20.9% at 72 weeks, and even the entry-level 5 mg dose reached 15.0% (Jastreboff et al. 2022).

Those trials ran separately, so careful readers refused to subtract one from the other. SURMOUNT-5 removed the excuse and landed almost exactly where the cross-trial math predicted: about 20% for tirzepatide, about 14% for semaglutide.

For a sense of how far the class has moved, semaglutide itself once buried the previous best-in-class GLP-1. In STEP 8, weekly semaglutide beat daily liraglutide 15.8% to 6.4%, and 70.9% of semaglutide patients hit at least 10% loss versus 25.6% on liraglutide (Rubino et al. 2022). Zepbound now sits a full tier above the drug that did that.

Bottom line: If maximum weight loss is the goal and you tolerate it, the head-to-head data favors Zepbound. Wegovy is not the loser here. It is the drug that redefined the category and still clears about 15%, which is more than most people actually need to change their health.

Where Wegovy still wins

Weight is one endpoint. Cardiovascular risk is another, and here semaglutide holds something tirzepatide has not yet matched with published outcomes data.

In SELECT, 17,604 adults with overweight or obesity and established cardiovascular disease but no diabetes took semaglutide 2.4 mg or placebo. Major adverse cardiovascular events fell from 8.0% to 6.5%, a hazard ratio of 0.80, roughly a 20% relative risk reduction over about 40 months of follow-up (Lincoff et al. 2023). That is a hard-outcome trial measuring fewer heart attacks and strokes, not just smaller numbers on a scale, and it is why Wegovy carries an FDA indication to reduce cardiovascular risk in that population.

Tirzepatide has its own cardiovascular outcomes trial running, but the results are not published yet. So if you or your clinician weigh a cardiac history heavily, Wegovy's evidence base is the more complete one today. Wegovy also launched two years earlier, which buys it more prescriber familiarity and, at various points, steadier supply.

Zepbound's second trick: sleep apnea

Zepbound's counterweight is that it treats a second approved condition. In SURMOUNT-OSA, tirzepatide reduced the apnea-hypopnea index (the number of breathing interruptions per hour of sleep) by roughly 25 to 29 events per hour in adults with moderate-to-severe obstructive sleep apnea and obesity (Malhotra et al. 2024). On the strength of that trial, Zepbound became the first drug ever approved for OSA, in late 2024.

If you carry both obesity and sleep apnea, that is not a tiebreaker, it is a real two-for-one. Wegovy has no OSA indication.

How the two dosing schedules differ

Both are once-weekly subcutaneous injections, and both climb slowly to blunt nausea. Wegovy steps up every four weeks through 0.25, 0.5, 1.0, and 1.7 mg before reaching the 2.4 mg maintenance dose around week 17. Zepbound starts at 2.5 mg and moves up in 2.5 mg increments no more often than every four weeks, with maintenance available at 5, 10, or 15 mg. The practical read: Zepbound gives your clinician more rungs to park you on if a lower dose already works, while Wegovy funnels most people toward its single top dose.

Side effects and tolerability

Both share the GLP-1 class profile: nausea, diarrhea, constipation, and occasional vomiting, worst during escalation and usually easing as your body adapts. In SURMOUNT-5, gastrointestinal effects were common on both arms and discontinuation rates were low and broadly similar. That detail matters, because it means Zepbound's larger results did not come at the cost of a brutal tolerability tradeoff.

The dual mechanism does not translate into dramatically worse side effects for most people. Slow titration is the lever that controls all of this on either drug, which is one more reason supervised dosing beats guessing your way up.

Warning: These are prescription medications with real contraindications, including a boxed warning for a personal or family history of medullary thyroid carcinoma or MEN 2. They are not research chemicals to self-source and self-dose. Screening, titration, and monitoring belong with a licensed clinician.

What they cost, and the cheaper supervised route

Pricing is the reason most people compare these at all. List prices for both run over a thousand dollars a month, but self-pay programs have reshaped the real number. Lilly sells self-pay Zepbound vials directly at a steep discount to list, and Novo Nordisk's self-pay Wegovy has landed in the ~$199 to 349 range depending on channel and month. Those figures move constantly, so treat them as a signal rather than a quote and confirm current numbers before you commit to anything.

The route most cost-conscious readers actually take is compounded GLP-1 through telehealth. Yucca Health connects you with US-licensed clinicians who review your history, confirm eligibility, and, if appropriate, have compounded semaglutide or tirzepatide filled by a US pharmacy and shipped to your door. It is the supervised, prescribed path without the in-person visit, and it typically undercuts brand pricing by a wide margin. We rank every access method by real per-month cost on the cheapest GLP-1 guide, with the specifics on compounded semaglutide online and compounded tirzepatide online.

If you are on Medicare or stuck between insurance plans, coverage for obesity drugs gets complicated fast. The Medicare GLP-1 bridge guide walks through the gaps and the legitimate workarounds.

Which one should you ask for?

Reach for Zepbound if raw weight loss is the priority, if you have obstructive sleep apnea, or if you plateaued on semaglutide and want the dual-mechanism ceiling. Reach for Wegovy if cardiovascular risk reduction is front of mind, if you value the longer track record, or if it is simply the drug your coverage or local supply favors this month.

Either way, the smart first move is a conversation with a clinician who can screen and titrate you, not a marketplace checkout. A supervised, prescribed program through Yucca Health gets you a real GLP-1 at a fraction of brand cost, and it is the route we point most readers toward on the cheapest GLP-1 guide. If your interest is strictly research rather than treatment, research-grade semaglutide and tirzepatide are covered separately, and Ascension Peptides sells lab-use vials with code ENHANCED for 50% off, though that path is not a substitute for supervised care.

For the diabetes-dose versions of this same rivalry, see Ozempic vs Wegovy, the same molecule at different doses, and Ozempic vs Mounjaro, the diabetes head-to-head that mirrors this one.

Disclaimer

This article is for educational purposes only and is not medical advice. Wegovy and Zepbound are prescription medications. Whether either is appropriate for you, and at what dose, is a decision for you and a licensed clinician who knows your history. Nothing here is a recommendation to obtain or use these drugs outside of medical supervision.