Wegovy is semaglutide; Zepbound is tirzepatide. Both are the obesity-approved versions of blockbuster drugs, both are once-weekly injections, and they were finally tested directly against each other. Zepbound won: about 20% average weight loss versus roughly 14% for Wegovy.
That does not make Wegovy a weak drug — it is highly effective and has a longer track record. It just came second in a head-to-head. Here is the full comparison: mechanism, the trial, side effects, cost in Canada, and which one to raise with your doctor.
The quick answer
For weight loss, Zepbound (tirzepatide) beats Wegovy (semaglutide) on average — and for once this is not an inference from separate studies but the result of a direct head-to-head trial. If the only question is “which takes off more weight,” the answer is Zepbound. Whether it is the right drug for you depends on tolerance, cost, coverage and your doctor’s judgement.
What each one is
Both are the obesity-branded versions of drugs that also treat diabetes under other names:
- Wegovy = semaglutide (same molecule as Ozempic), a GLP-1 receptor agonist — one hormone pathway.
- Zepbound = tirzepatide (same molecule as Mounjaro), a dual GLP-1 and GIP agonist — two hormone pathways.
That extra GIP receptor is the mechanistic reason tirzepatide tends to win. For the diabetes-branded version of the same rivalry, see Mounjaro vs Ozempic, and for the mechanism in depth, tirzepatide vs semaglutide.
This is the one matchup where you do not have to guess. SURMOUNT-5 put the two drugs head-to-head, and tirzepatide came out clearly ahead.Why Wegovy vs Zepbound is settled on weight
The head-to-head trial
The SURMOUNT-5 trial compared the two obesity drugs directly over 72 weeks. Tirzepatide produced about 20.2% average weight loss; semaglutide about 13.7%. Each also matched its own earlier pivotal trial (SURMOUNT-1 and STEP-1), so the result was no fluke.
| Zepbound (tirzepatide) | Wegovy (semaglutide) | |
|---|---|---|
| Receptors | GLP-1 + GIP | GLP-1 |
| Head-to-head loss | ~20.2% | ~13.7% |
| Own pivotal trial | ~20.9% (SURMOUNT-1) | ~14.9% (STEP-1) |
| Dosing | Once weekly | Once weekly |
Side effects compared
The profiles are very similar because both act on the same gut-hormone system. The common complaints for both are gastrointestinal — nausea, diarrhoea, constipation, vomiting and reflux — worst during dose escalation and easing with time. In the head-to-head trial, tolerability was broadly comparable, and discontinuation rates were similar. The rare serious risks (pancreatitis, gallbladder issues, the class thyroid-tumour warning) apply to both. Fast weight loss on either can bring muscle loss and facial volume loss.
Cost and access in Canada
Both are approved and available in Canada for weight management, dispensed by prescription. Coverage is the usual story: weight-loss use is rarely covered by public plans and varies privately, so many people pay out of pocket. Pricing shifts as generics arrive — see Sevmia, the generic Wegovy and generic Ozempic — and the broader money picture in weight-loss injections in Canada.
The research-compound angle
Both molecules also exist as research peptides — tirzepatide is listed at TrueLabs as TZ-2. As always, the research compound is a raw material for laboratory study, not the approved, dose-formulated drug, and carries no verified dose, sterile formulation or oversight. The trial figures here describe the prescription medicines, not research vials.
Wegovy vs Zepbound myths
“Myth: They are the same drug with different names.”
No. Wegovy is semaglutide; Zepbound is tirzepatide. Different molecules, different receptor counts.
“Myth: Zepbound is always the right choice.”
It wins on average weight loss, but tolerance, cost and coverage can make Wegovy the better fit for a given person.
“Myth: You can switch between them freely.”
Switching is a medical decision with its own dose considerations, managed by a clinician.
“Myth: Research tirzepatide equals Zepbound.”
It does not — no verified dose, formulation or approval. The prescription drug is the regulated version.
For researchers
TrueLabs supplies TZ-2 (tirzepatide) from $73, RT3 (retatrutide) from $90 and Cagrilintide from $40, in CAD for in vitro and laboratory research only. Before ordering, see how to read a peptide COA and the COA library.
FAQ
Tap a question to reveal the answer.
Is Zepbound better than Wegovy?
On weight loss, yes. In the head-to-head SURMOUNT-5 trial tirzepatide (Zepbound) produced about 20.2% versus 13.7% for semaglutide (Wegovy) over 72 weeks.
What is the difference between Wegovy and Zepbound?
Wegovy is semaglutide, which activates one receptor (GLP-1). Zepbound is tirzepatide, which activates two (GLP-1 and GIP). Both are once-weekly injections for weight management.
Are they the same as Ozempic and Mounjaro?
Same molecules, different brands. Wegovy and Ozempic are both semaglutide; Zepbound and Mounjaro are both tirzepatide. The obesity brands are Wegovy and Zepbound.
Which has fewer side effects?
Both cause mainly gastrointestinal effects, and head-to-head tolerability was broadly similar. There is no large difference, though individuals vary.
Which is cheaper in Canada?
Both are usually out of pocket for weight loss, and prices vary. Generic competition is starting to affect the semaglutide side. Check your plan and pharmacy.
Can I switch from Wegovy to Zepbound?
Possibly, but it is a medical decision with its own dose considerations and should be managed by your doctor.
Do you regain weight after stopping either?
Yes. Both show substantial regain after stopping, as with the GLP-1 class generally.
Is research tirzepatide the same as Zepbound?
No. Research tirzepatide (TrueLabs TZ-2) is a raw compound for laboratory use, not the approved, dose-formulated drug.
Related reading
- The complete GLP-1 drugs guide
- Mounjaro vs Ozempic
- Zepbound in Canada
- Tirzepatide vs semaglutide
- Sevmia: generic Wegovy
References
- Aronne LJ, et al. Tirzepatide versus Semaglutide for the Treatment of Obesity (SURMOUNT-5). N Engl J Med. 2025. NEJM
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387:205-216. NEJM
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP-1). N Engl J Med. 2021;384:989-1002. NEJM
This article summarizes published research and regulatory information for information only and is not medical advice. TrueLabs research compounds are sold for in vitro and laboratory research use only and are not intended for human or veterinary use.