Once you get past the brand names, every conversation about GLP-1 weight-loss medication comes down to two molecules: semaglutide and tirzepatide. Everything else — Ozempic, Wegovy, Mounjaro, Zepbound — is a label on one of those two.
We wrote about the brand names and what separates them already. This is the deeper version: what the head-to-head research actually found, where the difference does and doesn't matter, and how the choice gets made in a real assessment.
Semaglutide activates one receptor: GLP-1. In Canada it's sold as Ozempic (approved for type 2 diabetes) and Wegovy (approved for weight management, at higher doses).
Tirzepatide activates two: GLP-1 *and* GIP. In Canada it's sold as Mounjaro (approved for type 2 diabetes) and Zepbound (approved for weight management).
That brand distinction matters more than most people realize. Health Canada has approved six medications for long-term obesity management — liraglutide (Saxenda), naltrexone–bupropion (Contrave), orlistat (Xenical), semaglutide (Wegovy), tirzepatide (Zepbound), and setmelanotide (Imcivree) — and the weight-management approvals are Wegovy and Zepbound specifically, not their diabetes-labelled counterparts.
For years the comparison was indirect: you had semaglutide trials, you had tirzepatide trials, and people lined up the numbers from different studies with different participants. That's not a fair comparison.
SURMOUNT-5 changed that. It randomly assigned 751 adults with obesity but without type 2 diabetes to the maximum tolerated dose of either tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg), weekly for 72 weeks.
At 72 weeks:
The most common side effects in both groups were gastrointestinal, mostly mild to moderate, and mostly during dose escalation.
The placebo-controlled trials point the same direction. Semaglutide 2.4 mg produced a −14.9% weight change at 68 weeks versus −2.4% with placebo. Tirzepatide at 5, 10, and 15 mg produced −15.0%, −19.5%, and −20.9% at 72 weeks versus −3.1% with placebo.
So: on average, across large groups, tirzepatide produces more weight loss. That's the honest read of the evidence, and we're not going to pretend otherwise.
Averages describe populations. You are one person, and five things can move the answer:
1. The dose you can actually tolerate. Both trials measured maximum *tolerated* dose. If nausea keeps you at a low dose of one medication but you comfortably titrate up on the other, the trial average stops predicting your result. Tolerability is individual and not knowable in advance.
2. What else you're treating. Weight is rarely the only goal. Semaglutide and tirzepatide have different evidence bases across specific conditions — cardiovascular disease, heart failure with preserved ejection fraction, sleep apnea, fatty liver disease, prediabetes, type 2 diabetes. Canada's 2025 pharmacotherapy guideline is explicit that the decision should be informed by your adiposity-related health complications, not weight alone. Sometimes the medication with the smaller average weight effect is the better medication for *you* because of what else it treats.
3. Cost and coverage. These medications differ in price, and private plans cover them differently. A medication you can afford to stay on for two years beats a slightly more effective one you stop after four months.
4. Availability. Supply of these products has fluctuated. The best plan is one you can actually fill.
5. Your preferences. Injection frequency, device, side-effect profile, how you feel about each option. The guideline names patient values and preferences as part of the decision, not a footnote to it.
Both are gut-hormone medications, so the side-effect profile is largely the same family: nausea, vomiting, diarrhea, constipation. Mostly mild to moderate, mostly during dose escalation, and mostly manageable with slow titration.
In the semaglutide trial, side effects led 4.5% of participants to stop, versus 0.8% on placebo. Rarer effects included gallbladder issues (2.6% vs 1.2% with placebo) and pancreatitis (0.2% vs 0%). In the tirzepatide trial, discontinuation rates were 4.3%, 7.1%, and 6.2% at the 5, 10, and 15 mg doses.
Two things follow from that. First, most people don't quit over side effects. Second, the single biggest lever on whether you tolerate treatment is how the dose is escalated — which is a program decision, not a drug property. We cover the practical side in our guide to managing GLP-1 side effects.
You'll see compounded semaglutide and tirzepatide advertised at lower prices. Canadian obesity guidance is direct that compounded products and products not approved for obesity treatment should not be used. They are not the approved medications, quality and dosing accuracy vary, and there is no manufacturer accountability behind them. If cost is the obstacle, tell us — there are legitimate ways to work on that, and this isn't one of them.
This is the point that gets lost in the comparison. These medications treat obesity as the chronic condition it is. Stopping generally leads to weight regain and loss of the health benefits that came with it. The Canadian guideline supports long-term use for both weight loss and maintenance.
Choosing between semaglutide and tirzepatide is therefore less like picking a diet and more like picking a blood-pressure medication: the question is what you can stay on, safely and affordably, for years.
At Edgemont Weight Management Clinic, the decision comes out of an assessment, not a preference form. We look at your health history, your weight-related health conditions, your other medications, what your coverage looks like, and what you want out of treatment. Then we recommend an option — and we say why.
If the first choice doesn't suit you, that's information, not failure. Switching between these medications under supervision is a normal part of care, and it's one of the reasons ongoing follow-up matters more than the initial pick.
Our medically supervised program includes the assessment, the prescription where appropriate, dose titration, side-effect management, and regular follow-up.
Is tirzepatide better than semaglutide?
On average, for weight loss, the head-to-head evidence says yes — 20.2% versus 13.7% at 72 weeks in SURMOUNT-5. But "better on average" is not the same as "better for you." Tolerability, your other health conditions, cost, coverage, and availability all factor into the right choice.
What's the difference between Wegovy and Zepbound?
Wegovy is semaglutide; Zepbound is tirzepatide. Both are approved by Health Canada for long-term weight management. Ozempic and Mounjaro are the same two molecules approved for type 2 diabetes instead.
Can I switch from one to the other?
Yes, under medical supervision, and it's fairly common — usually because of tolerance, response, cost, or availability. It should be planned rather than improvised, since dosing does not transfer one-to-one.
How long will I need to be on it?
Think in years, not months. Obesity is a chronic condition, and stopping treatment generally leads to weight regain. The goal is a plan you can sustain.
What if I can't tolerate the higher doses?
That's common and manageable. Slower titration usually helps, and many people reach meaningful results below the maximum dose. The dose should be tailored to your goals and tolerance, not pushed to the label maximum by default.
Do I need a referral?
No. Book a consultation directly with our pharmacist-led team in NW Calgary.
*Medically reviewed by Wessam Sakr, BScPharm. This article is general information, not medical advice for your specific situation. Talk to a healthcare professional about what's right for you.*
Ready to talk to a professional? Book a consultation with our pharmacist-led team to find the right medically supervised approach for you.