Semaglutide vs. tirzepatide: one is the most-studied option, and one produced the biggest average weight loss in trials. Here's how they actually compare, side by side.
If you've been researching GLP-1 medications, you've probably hit a wall of brand names — Ozempic, Wegovy, Mounjaro, Zepbound — and the honest question underneath all of it: which medication should I actually take? That's the question we get asked most at Better Off, and it deserves a straight answer instead of marketing. So here is the honest, trial-by-trial comparison of semaglutide and tirzepatide, what the studies found, and how we'd help you decide between them.
The 30-second version
Both medications are once-weekly injectables. Semaglutide (sold as Wegovy for weight loss and Ozempic for type 2 diabetes) mimics one hormone — GLP-1. Tirzepatide (sold as Zepbound for weight loss and Mounjaro for type 2 diabetes) mimics two — GLP-1 and GIP — and because of that dual action it has produced larger average weight loss in clinical trials. The tradeoff: tirzepatide is newer, so there's a shorter track record, and semaglutide has more long-term data behind it. Both work, and the right one depends on your body, your health history, and your budget — not on which name you've heard more often.
How each medication works
Your body makes a hormone called GLP-1 every time you eat. It tells your stomach to slow down, tells your brain you're satisfied sooner, and helps regulate blood sugar. Semaglutide is a long-acting version of that signal: one weekly injection keeps the effect steady all week.
Tirzepatide does the same thing and adds a second hormone — GIP. GIP works alongside GLP-1 in how your body processes energy and fat, and the two together appear to amplify the effect. That's why you'll see tirzepatide described as a "dual agonist" — it hits two receptors instead of one.
What the trials found: weight loss
This is the comparison most people care about, and the numbers come from three large, published trials.
The STEP 1 trial (New England Journal of Medicine, 2021) studied semaglutide 2.4 mg — the Wegovy dose — in adults with overweight or obesity over 68 weeks. The semaglutide group lost an average of 14.9% of their starting body weight, versus 2.4% with lifestyle changes alone. Half of the semaglutide group lost 15% or more.
The SURMOUNT-1 trial (New England Journal of Medicine, 2022) studied tirzepatide in adults with obesity over 72 weeks. Average weight loss was 15.0% at the 5 mg dose, 19.5% at 10 mg, and 20.9% at the 15 mg dose — versus 3.1% with placebo. About 9 in 10 participants on tirzepatide lost at least 5%.
And the SURPASS-2 trial (New England Journal of Medicine, 2021) is the rare head-to-head: tirzepatide against semaglutide directly, in people with type 2 diabetes, over 40 weeks. Tirzepatide produced greater weight loss at every dose — an average of 1.9 to 5.5 kg more than semaglutide.
| Trial | Medication | Average weight loss | Duration |
|---|---|---|---|
| STEP 1 (2021) | Semaglutide 2.4 mg | 14.9% of body weight | 68 weeks |
| SURMOUNT-1 (2022) | Tirzepatide 5–15 mg | 15.0% to 20.9% | 72 weeks |
| SURPASS-2 (2021) | Head-to-head, type 2 diabetes | Tirzepatide ahead by 1.9–5.5 kg | 40 weeks |
One honest caveat: STEP 1 and SURMOUNT-1 studied different groups of people, so comparing 14.9% to 20.9% across trials is a rough guide, not a guarantee. SURPASS-2 is the closest apples-to-apples comparison we have, and it favored tirzepatide. Individual results vary — a lot — and that's exactly why the starting point is always a medical evaluation, not a menu.
Side effects: more alike than different
Both medications share the same basic side-effect profile, because both slow digestion. The most common effects are nausea, diarrhea, constipation, and stomach upset — usually in the first weeks, and usually mild to moderate. In the trials above, these were the most common adverse events for both drugs, and for most people they fade as the body adjusts.
There are real reasons some people should avoid either medication — a personal or family history of certain thyroid cancers, pancreatitis, pregnancy, or gastroparesis, among others. This is the part where a provider's evaluation matters: it's not a question of which drug is "safer," it's which one is right for your specific history. Both medications are provider-prescribed and provider-monitored at Better Off for exactly this reason.
Cost, honestly
For most people paying out of pocket, semaglutide is the more affordable of the two, and that's a legitimate factor in the decision — a medication you can't sustain financially isn't the right medication. We publish our program pricing on our weight loss program page, and we'll walk through the real monthly cost of each option at your consult, including manufacturer savings programs that can change the picture. Our longer guide on GLP-1 costs without insurance breaks down list prices, savings programs, and what to watch out for.
So which one should you take?
After years of prescribing both, here's how we think about it:
- You may lean semaglutide if you want the longest track record, a lower price point, or if you've been told your history calls for the most conservative option. It works, and it has the deepest pile of long-term data behind it.
- You may lean tirzepatide if maximizing weight loss is the priority and your health history clears it for use, or if you tried semaglutide and hit a plateau that doesn't move.
- Either way, the medication is one part of the program. The people who do best pair it with nutrition support and follow-up — which is why our program includes both, not just the prescription.
The bottom line
Semaglutide and tirzepatide are both effective, well-studied options — tirzepatide has shown larger average weight loss, semaglutide has more years of data behind it. The right choice is the one that fits your health history, your goals, and your budget, decided with a provider who knows all three. Book a consultation at Better Off and we'll figure out together which one that is.
References:
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine, 2021; 384:989-1002.
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine, 2022; 387:205-216.
- Frias JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). New England Journal of Medicine, 2021; 385:503-515.