Tirzepatide vs. Semaglutide: Head-to-Head Comparison
Tirzepatide and semaglutide are the two most prescribed weight loss medications in the world. Both are once-weekly injections. Both suppress appetite. But they are not the same — and a landmark 2025 trial finally compared them directly.
Table of Contents
Quick Answer
Tirzepatide produces significantly more weight loss than semaglutide. In the head-to-head SURMOUNT-5 trial, tirzepatide delivered 20.2% weight loss vs. 13.7% for semaglutide — that's 47% more weight loss. Tirzepatide also had fewer GI-related discontinuations.
However, semaglutide may still be the better choice for some people depending on cost, insurance coverage, availability, and individual response.
Head-to-Head Comparison Table
| Tirzepatide | Semaglutide | |
|---|---|---|
| Brand Names | Mounjaro, Zepbound | Ozempic, Wegovy |
| Manufacturer | Eli Lilly | Novo Nordisk |
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist only |
| FDA Approved (Weight Loss) | Nov 2023 | Jun 2021 |
| Max Approved Dose | 15 mg/week | 2.4 mg/week (7.2 mg HD) |
| Avg. Weight Loss (head-to-head) | 20.2% ↑ | 13.7% |
| Avg. Pounds Lost (head-to-head) | 50.3 lbs ↑ | 33.1 lbs |
| Waist Circumference Reduction | −18.4 cm ↑ | −13.0 cm |
| ≥10% Weight Loss | 86% ↑ | 69% |
| ≥20% Weight Loss | 63% ↑ | 32% |
| GI Discontinuation Rate | 2.7% (better) | 5.6% |
| Administration | Weekly injection | Weekly injection or oral |
| Oral Option | ❌ Not yet | ✅ Approved Jan 2026 |
| List Price | ~$1,069/month | ~$1,349/month (Wegovy) |
| Compounded Price | $349–699/month | $150–500/month |
| Thyroid Cancer Warning | ⚠️ Yes (rodent data) | ⚠️ Yes (rodent data) |
Head-to-head data from SURMOUNT-5 (Aronne et al., NEJM 2025). Individual trial data from SURMOUNT-1 and STEP 1. ↑ indicates better outcome.
How They Differ: Mechanism of Action
The fundamental difference is simple: semaglutide targets one hormonal pathway; tirzepatide targets two.
Semaglutide (GLP-1 only)
- •Suppresses appetite in the brain
- •Slows gastric emptying
- •Improves insulin secretion
- •Reduces glucagon
Tirzepatide (GLP-1 + GIP)
- •All of the GLP-1 effects above, plus:
- •GIP enhances appetite suppression
- •Improves insulin sensitivity
- •May promote fat oxidation
- •Creates complementary metabolic effects
Think of it this way: semaglutide is a single-action tool. Tirzepatide is a multi-tool that works on two fronts simultaneously — and the clinical data confirms this translates into meaningfully greater weight loss.
The Clinical Evidence: SURMOUNT-5
Until 2025, comparisons between tirzepatide and semaglutide relied on cross-trial analysis — comparing SURMOUNT results to STEP results in different patient populations. SURMOUNT-5 changed that.
SURMOUNT-5 Study Design
Published
NEJM, 2025
Participants
751 adults
Duration
72 weeks
Sites
32 U.S. locations
Adults with obesity (BMI ≥30 or ≥27 with comorbidities), without diabetes. Randomized to maximum tolerated dose of tirzepatide (10–15 mg) OR semaglutide (1.7–2.4 mg). No placebo — direct active comparison.
Key Findings
Weight Loss
20.2%
Tirzepatide average
13.7%
Semaglutide average
47% more weight loss with tirzepatide (p<0.001)
For a 250-Pound Person
~50 lbs lost
Tirzepatide → finish at ~200 lbs
~34 lbs lost
Semaglutide → finish at ~216 lbs
| Metric | Tirzepatide | Semaglutide |
|---|---|---|
| Avg. weight loss | 20.2% | 13.7% |
| Avg. weight lost | 22.8 kg (50.3 lbs) | 15.0 kg (33.1 lbs) |
| Waist circumference | −18.4 cm | −13.0 cm |
| GI discontinuation | 2.7% | 5.6% |
Notable finding:
Both drugs produced approximately 6% less weight loss in men than women. This trial had 35% male participants — higher than most obesity trials — making this a particularly informative finding for male patients.
Side Effects Comparison
Both drugs share a similar GI-heavy side effect profile. The differences are subtle.
| Side Effect | Tirzepatide | Semaglutide |
|---|---|---|
| Nausea | Common (peaks during escalation) | Common (peaks during escalation) |
| Diarrhea | Common | Common |
| Constipation | Common | Common |
| Vomiting | Less common | More common at higher doses |
| GI Discontinuation | 2.7% (better tolerated) | 5.6% |
| Pancreatitis Risk | Rare | Rare |
| Gallbladder Issues | Possible (rapid weight loss) | Possible (rapid weight loss) |
| Thyroid Warning | ⚠️ Black box | ⚠️ Black box |
Bottom line on side effects: Both cause GI issues, but tirzepatide appears to be somewhat better tolerated — fewer people quit due to side effects in the head-to-head trial. Despite being more effective, tirzepatide was actually better tolerated.
Cost Comparison
| Option | Tirzepatide | Semaglutide |
|---|---|---|
| Brand list price | ~$1,069/month (Zepbound) | ~$1,349/month (Wegovy) |
| With savings card | As low as $25/month | Varies by program |
| Compounded | $349–699/month | $150–500/month |
| Insurance coverage | Growing, inconsistent | More established |
Key cost considerations:
- Semaglutide has been on the market longer, so insurance coverage tends to be better
- Eli Lilly's savings card for Zepbound can be very aggressive ($25/month for eligible patients)
- Compounded semaglutide is generally cheaper than compounded tirzepatide
- Both drugs require long-term use — annual costs add up significantly
Who Should Choose Which?
Choose Tirzepatide if:
- ✓You want the maximum weight loss from an FDA-approved medication
- ✓You have insurance that covers Zepbound, or qualify for Eli Lilly’s savings card
- ✓You previously tried semaglutide and didn’t lose enough weight
- ✓You had significant GI side effects on semaglutide (tirzepatide may be better tolerated)
- ✓You also have type 2 diabetes (dual mechanism provides additional metabolic benefits)
Choose Semaglutide if:
- ✓Your insurance covers Wegovy but not Zepbound
- ✓Cost is a major factor (compounded semaglutide is cheaper)
- ✓You prefer an oral option (oral semaglutide approved January 2026)
- ✓You’re already on semaglutide and getting good results — no need to switch
- ✓You want the longest safety track record (more years of real-world data)
- ✓Semaglutide is more readily available in your area
What About Retatrutide?
Both tirzepatide and semaglutide may eventually be surpassed by retatrutide — a triple agonist (GLP-1 + GIP + Glucagon) that showed 28.7% average weight lossin Phase 2 trials. It's currently in Phase 3 trials and not yet FDA-approved.
Read our Retatrutide guide →The Bottom Line
Tirzepatide is the more effective medication. The SURMOUNT-5 trial leaves no room for debate: at maximum doses, tirzepatide produces significantly more weight loss than semaglutide, with better tolerability.
But “more effective” doesn't always mean “best for you.” Semaglutide is still an excellent medication that has helped millions of people lose significant weight. If semaglutide is what your insurance covers, what's available, or what you can afford — it's still a strong choice. A 13.7% weight loss is life-changing for most people. The real question isn't which drug is better in a trial. It's which drug you can access, afford, and sustain long-term.
Sources
- 1.Aronne LJ, et al. "Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5)." N Engl J Med. 2025;393(1):26-36.
- 2.Jastreboff AM, et al. "Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)." N Engl J Med. 2022;387(4):327-340.
- 3.Wilding JPH, et al. "Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1)." N Engl J Med. 2021;384(11):989-1002.
- 4.Aronne LJ, et al. "Continued Treatment With Tirzepatide for Maintenance of Weight Reduction (SURMOUNT-4)." JAMA. 2024;331(1):38-48.
- 5.Rubino D, et al. "Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance (STEP 4)." JAMA. 2021;325(14):1414-1425.
- 6.Rodriguez PJ, et al. "Semaglutide vs Tirzepatide for Weight Loss in Adults With Overweight or Obesity." JAMA Intern Med. 2024;184(9):1056-1064.
- 7.Greenway FL. "Tirzepatide versus Semaglutide for Obesity (Editorial)." N Engl J Med. 2025;393(1):86-87.