Tirzepatide (Zepbound, Mounjaro) and semaglutide (Wegovy, Ozempic) are the two biggest weight-loss drugs in the world — and in 2025 they were finally tested head-to-head. In SURMOUNT-5, tirzepatide produced 20.2% weight loss versus 13.7% for semaglutide over 72 weeks. Tirzepatide won on the scale.
But “more weight loss” is not the only thing that matters. Semaglutide has a longer track record, strong cardiovascular data, a pill version, and — in Canada as of 2026 — cheap generics. Here is the honest comparison.
The quick answer
On weight loss, tirzepatide is the stronger drug — that is settled by a direct trial, not a guess. But semaglutide is not far behind and brings things tirzepatide does not: more years of real-world use, established cardiovascular-benefit data, an oral option, and the first wave of low-cost generics in Canada.
So the right answer to “which is better?” is “better at what?” For maximum scale movement, tirzepatide. For cost, track record and flexibility, semaglutide has real arguments. The newer triple agonist retatrutide is coming for both, as we cover in retatrutide vs tirzepatide vs semaglutide.
Tirzepatide wins the weigh-in. Semaglutide wins on everything that isn’t the number on the scale — price, history, and a pill.Tirzepatide vs semaglutide, in a line
The brand-name maze
Half the confusion here is naming. Each molecule is sold under different brands for different uses:
| Molecule | Weight-loss brand | Diabetes brand | Pill |
|---|---|---|---|
| Tirzepatide (Eli Lilly) | Zepbound | Mounjaro | None yet |
| Semaglutide (Novo Nordisk) | Wegovy | Ozempic | Oral Wegovy / Rybelsus |
So “Zepbound vs Wegovy” and “Mounjaro vs Ozempic” are both really just tirzepatide vs semaglutide, in different packaging.
How they work
Both are once-weekly injectable incretin drugs, but they hit a different number of targets.
- Semaglutide is a single GLP-1 receptor agonist. It curbs appetite, slows stomach emptying and improves blood sugar.
- Tirzepatide is a dual agonist: it adds GIP, a second incretin hormone, on top of GLP-1. That second target is widely credited for its larger weight-loss effect.
One extra receptor is the whole mechanical difference — and in this class, that extra target has translated into bigger numbers.
SURMOUNT-5: the head-to-head
For years, “tirzepatide vs semaglutide” was answered with numbers from separate trials. SURMOUNT-5 changed that by testing them directly, and the full results were published in 2025.
| SURMOUNT-5 (72 weeks, 751 adults) | Result |
|---|---|
| Tirzepatide weight loss | 20.2% |
| Semaglutide weight loss | 13.7% |
| Reached at least 25% weight loss | ~31% vs 16.1% |
Tirzepatide did not just edge it — it was meaningfully ahead, and roughly twice as many people hit the 25%-loss mark. This is the cleanest evidence we have that, dose for dose at the top of the range, tirzepatide moves the scale more than semaglutide.
In a head-to-head trial, tirzepatide took off about a third more weight than semaglutide. That is the gap in plain terms.SURMOUNT-5, simplified
Where semaglutide still wins
If tirzepatide loses more weight, why would anyone choose semaglutide? Several real reasons:
- Track record. Semaglutide has been in wide use longer, so clinicians have more real-world experience with it.
- Cardiovascular data. Semaglutide has established outcome data showing cardiovascular benefit in certain patients — a factor that can matter as much as weight for some people.
- A pill. Semaglutide comes in oral forms (an oral weight-loss version was approved by the FDA in late 2025; Rybelsus exists for diabetes). Tirzepatide has no approved pill yet.
- Price. In Canada, generic semaglutide arrived in 2026 and is far cheaper than it was. Tirzepatide has no generic competition yet. See Sevmia and generic Wegovy in Canada.
For a patient weighing cost, a cardiovascular history, or a preference to avoid injections, semaglutide can be the better practical choice even though it loses the weight-loss race on paper.
Side effects
Both drugs share the same family of side effects: nausea, vomiting, diarrhea and constipation, usually worst when starting or increasing the dose and easing over time. Because tirzepatide drives more weight loss, some effects can be more pronounced, but the profiles are broadly similar in kind. Both carry class warnings that a prescriber will review.
The honest summary: neither is “safer” in a simple way. The right choice depends on the individual, which is a conversation for a doctor or pharmacist, not a blog. None of this is medical advice.
Cost and availability in Canada
Both tirzepatide and semaglutide are approved, prescription medicines in Canada, accessed through a clinician. The big 2026 shift is price: generic semaglutide reached Canadian pharmacies in May 2026 at roughly a third of the brand price, with a generic Wegovy equivalent (Sevmia) approved in June. Tirzepatide, being newer, has no generic yet, so it generally remains the pricier option.
As always, the legal routes are approved products through a prescription, or clinical trials. Research-grade material sold for laboratory use is a separate category that is not for human use, and Health Canada’s 2026 advisory was explicit that unauthorized injectable peptides bought online are illegal, research-use label or not.
Myths
“Myth: Tirzepatide is just a stronger Ozempic.”
They are different molecules from different companies. Tirzepatide adds a second receptor target (GIP) to the GLP-1 base that semaglutide uses alone. It is not a higher dose of the same drug.
“Myth: Since tirzepatide wins, nobody should use semaglutide.”
Semaglutide has a longer track record, cardiovascular outcome data, oral options and, in Canada, cheap generics. For many people those factors outweigh a few extra percentage points of weight loss.
“Myth: Zepbound, Mounjaro, Wegovy and Ozempic are four different drugs.”
They are two drugs. Zepbound and Mounjaro are both tirzepatide; Wegovy and Ozempic are both semaglutide. The brand just signals whether it is approved for weight loss or diabetes.
“Myth: The research-grade versions are the same as the prescription drug.”
Research-grade peptides are sold for laboratory use only, are not quality-assured for human use, and are not legal to inject in Canada. The approved prescription products are a different thing entirely.
For researchers
For laboratory pharmacology work on incretin biology, TrueLabs supplies reference peptides in CAD, for in vitro and laboratory research only, never for human or veterinary use, including TZ-2 (tirzepatide) from $73 and RT3 (retatrutide) from $90. Confirm identity and purity against a lot-matched certificate — see how to read a peptide COA and the COA library.
FAQ
Tap a question to reveal the answer.
Is tirzepatide or semaglutide better for weight loss?
In the SURMOUNT-5 head-to-head, tirzepatide won: 20.2% weight loss versus 13.7% for semaglutide over 72 weeks, with about twice as many people reaching 25% loss. Tirzepatide is the stronger scale-mover, though semaglutide has other advantages.
Are Zepbound and Wegovy the same as Mounjaro and Ozempic?
Zepbound and Mounjaro are both tirzepatide; Wegovy and Ozempic are both semaglutide. The weight-loss brands (Zepbound, Wegovy) and diabetes brands (Mounjaro, Ozempic) are the same molecules approved for different uses.
What is the difference between tirzepatide and semaglutide?
Semaglutide is a single GLP-1 receptor agonist. Tirzepatide is a dual agonist that also targets GIP. That extra target is widely credited for tirzepatide’s larger weight-loss effect.
Why would anyone choose semaglutide if tirzepatide works better?
Semaglutide has a longer track record, established cardiovascular-benefit data, oral options, and cheaper generics in Canada as of 2026. For cost, a cardiac history, or pill preference, it can be the better practical choice.
Do they have different side effects?
They share the same class of gastrointestinal effects: nausea, vomiting, diarrhea, constipation, usually worst at dose changes. Neither is simply “safer”; suitability depends on the person and is a decision for a prescriber.
Is there a tirzepatide pill?
Not yet. Semaglutide has oral forms (an oral weight-loss version was approved by the FDA in late 2025, plus Rybelsus for diabetes), but tirzepatide has no approved pill as of October 2026.
Which is cheaper in Canada?
Semaglutide, now that generics have arrived (2026) at roughly a third of the brand price. Tirzepatide has no generic competition yet, so it generally remains more expensive.
Can I buy either as a research peptide?
Research-grade tirzepatide and related peptides are sold for laboratory research use only, never for human use. The approved prescription products are accessed through a pharmacy; unauthorized injectable peptides bought online are illegal in Canada.
Related reading
- Retatrutide vs tirzepatide vs semaglutide
- CagriSema vs tirzepatide
- Sevmia and generic Wegovy in Canada
- Tirzepatide research in Canada
- What is retatrutide?
References
- Tirzepatide bests semaglutide for weight loss: SURMOUNT-5 (20.2% vs 13.7%, 72 weeks, 751 adults; published 2025). TCTMD. TCTMD
- Zepbound (tirzepatide) showed superior weight loss over Wegovy (semaglutide) in complete SURMOUNT-5 results. Drugs.com clinical trials. Drugs.com
- Health Canada. Think twice before injecting peptides bought online (advisory, April 9, 2026). Health Canada
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.