The semaglutide vs tirzepatide debate finally has a head-to-head answer. In the SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, adults with obesity taking tirzepatide lost an average of 20.2% of their body weight over 72 weeks. Those taking semaglutide lost 13.7%. That is the clearest result in weight-loss medicine today: tirzepatide produces more average weight loss. But averages are not the whole decision. Semaglutide is usually cheaper, has a longer track record, and works well for millions of people. Here is what the data actually shows, number by number.
Semaglutide vs Tirzepatide: The One-Minute Answer
Both drugs are once-weekly injections you take under the skin of your stomach, thigh, or upper arm. Both were built for type 2 diabetes first and approved for weight loss later.
Semaglutide is made by Novo Nordisk. It is sold as Ozempic for diabetes and Wegovy for chronic weight management — the FDA approved Wegovy in June 2021 as the first new weight-management drug since 2014. Tirzepatide is made by Eli Lilly. It is sold as Mounjaro for diabetes and Zepbound for weight management, approved by the FDA in November 2023.
The short version of the comparison: tirzepatide wins on average weight loss in every trial that measured it. Semaglutide fights back on price, availability, and years of real-world use. Side effects are nearly identical between the two.
How They Work: One Gut Hormone vs Two
Semaglutide is a GLP-1 receptor agonist. Per the Cleveland Clinic, drugs in this class mimic a natural gut hormone called GLP-1: they trigger insulin release, slow how fast food leaves your stomach, and turn down appetite signals in the brain. You feel full sooner and stay full longer, so you eat less without white-knuckle willpower.
Tirzepatide does all of that — and adds a second target. It activates both GIP and GLP-1 receptors, which is why the FDA’s approval announcement for Zepbound describes it as activating two hormone receptors from the intestine to reduce appetite and food intake. GIP is another gut hormone involved in how your body handles food and stores fat.
That second mechanism is the leading explanation for the gap in results. It is not that semaglutide is weak — a ~14.9% average loss was groundbreaking in 2021. Tirzepatide simply pulls a second lever at the same time.
What the Trials Show: STEP 1, SURMOUNT-1, and the Head-to-Head
Three trials tell the whole story. All three enrolled adults with obesity (or overweight plus a weight-related condition) who did not have diabetes, and all three paired the drug with a reduced-calorie diet and increased activity.
| Trial | Drug and dose | Length | Average weight loss | Placebo group |
|---|---|---|---|---|
| STEP 1 (2021) | Semaglutide 2.4 mg weekly | 68 weeks | 14.9% | 2.4% |
| SURMOUNT-1 (2022) | Tirzepatide 5 mg weekly | 72 weeks | 15.0% | 3.1% |
| SURMOUNT-1 (2022) | Tirzepatide 10 mg weekly | 72 weeks | 19.5% | 3.1% |
| SURMOUNT-1 (2022) | Tirzepatide 15 mg weekly | 72 weeks | 20.9% | 3.1% |
| SURMOUNT-5 (2025) | Tirzepatide vs semaglutide, head-to-head | 72 weeks | 20.2% vs 13.7% | none |
Notice something useful in that table: tirzepatide’s lowest dose (5 mg) roughly matched semaglutide’s highest dose (2.4 mg) — about 15% average loss for each. The higher tirzepatide doses then pulled away.
For years, the honest caveat was that STEP 1 and SURMOUNT-1 were different trials with different people, so the numbers could not be compared directly. SURMOUNT-5 closed that gap by testing both drugs in the same trial at the same time. The result — 20.2% versus 13.7% at 72 weeks — landed almost exactly where the separate trials pointed.
One thing these averages hide: individual spread. Some people lose far more than the average on either drug, and some lose much less. No clinician can promise you a specific number, and neither can we.
Semaglutide vs Tirzepatide: Side-by-Side Comparison
Here is the full comparison in one table, including side effects and typical 2026 costs.
| Feature | Semaglutide | Tirzepatide |
|---|---|---|
| Mechanism | GLP-1 receptor agonist | Dual GIP + GLP-1 receptor agonist |
| Weight-loss brand | Wegovy (FDA-approved June 2021) | Zepbound (FDA-approved November 2023) |
| Diabetes brand | Ozempic | Mounjaro |
| Manufacturer | Novo Nordisk | Eli Lilly |
| Dosing range | 0.25 mg up to 2.4 mg weekly | 2.5 mg up to 15 mg weekly |
| Pivotal trial result | ~14.9% avg loss at 68 weeks (STEP 1) | Up to ~20.9% avg loss at 72 weeks (SURMOUNT-1) |
| Head-to-head (SURMOUNT-5) | 13.7% at 72 weeks | 20.2% at 72 weeks |
| Most common side effects | Nausea, diarrhea, vomiting, constipation | Nausea, diarrhea, vomiting, constipation |
| Quit due to side effects in trial | 4.5% (GI events, STEP 1) | 4.3–7.1% by dose (SURMOUNT-1) |
| Compounded cash price (not FDA-approved) | ~$99–$299/month | ~$149–$449/month |
| Brand-name cash price | ~$1,300+/mo retail; ~$199–$399/mo via telehealth + membership | From ~$299/mo via telehealth + membership |
Dosing: Two Very Different Ladders
Both drugs start low and climb slowly, because gradual increases are what keep the stomach side effects tolerable. But the ladders look nothing alike, which matters if you ever switch drugs.
Per the Wegovy prescribing information, semaglutide starts at 0.25 mg weekly and steps up every 4 weeks — 0.5 mg, 1 mg, 1.7 mg — reaching the 2.4 mg maintenance dose around week 17. Tirzepatide starts at 2.5 mg weekly, and per the FDA’s Zepbound approval, the dose is increased over 4 to 20 weeks to reach a target of 5 mg, 10 mg, or 15 mg once weekly.
The numbers are on different scales entirely — 2.5 mg of tirzepatide is a starting dose, while 2.4 mg of semaglutide is the maximum. That is why switching between the drugs requires a clinician to restart the titration, not a milligram-for-milligram trade. Our tirzepatide dosage chart maps the full escalation schedule week by week.
Side Effects: Same Family, Slightly Different Odds
Because both drugs slow digestion and act on the gut, their side effects overlap almost completely. In STEP 1, nausea and diarrhea were the most common problems with semaglutide — typically transient, mild to moderate, and fading with time. In SURMOUNT-1, the most common adverse events with tirzepatide were also gastrointestinal, mostly mild to moderate, and concentrated during dose escalation.
The dropout numbers put the difference in perspective. 4.5% of semaglutide users in STEP 1 stopped treatment because of gastrointestinal events, versus 0.8% on placebo. In SURMOUNT-1, adverse events caused 4.3%, 7.1%, and 6.2% of participants on the 5 mg, 10 mg, and 15 mg tirzepatide doses to stop, versus 2.6% on placebo. Higher tirzepatide doses meant somewhat higher dropout — but the large majority of people on either drug stayed the course.
Both drugs carry the same boxed warning: thyroid C-cell tumors appeared in rodent studies, so neither should be used by anyone with a personal or family history of medullary thyroid carcinoma or MEN 2 syndrome. Both labels also warn about pancreatitis and gallbladder problems, and neither drug should be used during pregnancy. For a symptom-by-symptom management plan, see our GLP-1 side effects guide.
Cost: Where Semaglutide Fights Back
If tirzepatide wins the effectiveness column, semaglutide usually wins the price column — and for many people, that decides it.
At retail without insurance, brand-name Wegovy runs about $1,300+ per month, while telehealth cash-pay programs sell it for roughly $199 to $399 a month plus membership fees. Brand-name Zepbound starts around $299 a month plus membership through some telehealth providers, with retail cash listings far higher. Insurance coverage for weight-loss drugs remains inconsistent, and many employer plans exclude the category entirely.
The compounded market is where most cash payers end up, and the semaglutide vs tirzepatide price gap persists there. Compounded semaglutide runs about $99 to $299 per month through telehealth providers, while compounded tirzepatide runs about $149 to $449 per month — often $50 to $150 more than semaglutide at the same provider. Two warnings apply. First, compounded semaglutide and tirzepatide are not FDA-approved, and the FDA has flagged dosing errors and adverse-event reports tied to compounded GLP-1 drugs, so pharmacy sourcing matters enormously. Second, prices for the same molecule vary by hundreds of dollars a month between providers. Our rankings of the best places to get tirzepatide online and the best compounded semaglutide programs compare verified prices, pharmacy disclosure, and complaint records side by side.
Which One Should You Choose?
Pick based on your goal, your budget, and your clinician’s judgment — in that order.
Tirzepatide makes sense if maximum average weight loss is the priority and you can absorb the higher cost. The head-to-head data is unambiguous: about 6.5 percentage points more body weight lost over 72 weeks. For someone starting at 250 pounds, that difference averages out to roughly 16 additional pounds.
Semaglutide makes sense if budget drives the decision, your insurance covers Wegovy but not Zepbound, or you want the molecule with the longest weight-management track record — Wegovy has been FDA-approved since 2021 and studied in a large trial program since before that.
And remember what both drug labels assume: these medications were tested alongside a reduced-calorie diet and increased physical activity, and they are long-term treatments — stopping either one commonly leads to weight regain. The right drug is the one you can afford to stay on, tolerate well, and pair with habits that hold. A licensed clinician who knows your history should make the final call.