Comparison
Tirzepatide Versus Semaglutide
SURMOUNT-5 compared the two directly in 751 adults with obesity and without diabetes over 72 weeks at maximum tolerated doses. Tirzepatide produced greater weight and waist reduction (waist -18.4 cm versus -13.0 cm) and lower gastrointestinal discontinuation (2.7% versus 5.6%). Semaglutide retains distinct cardiovascular-outcome evidence.
Key takeaways
- SURMOUNT-5 is a direct head-to-head randomised trial, not a cross-trial comparison.
- Tirzepatide produced greater weight and waist reduction at 72 weeks.
- Gastrointestinal discontinuation was lower with tirzepatide (2.7%) than semaglutide (5.6%).
- Mechanism differs: tirzepatide is a dual GIP/GLP-1 agonist, semaglutide a GLP-1 agonist.
- Superiority on weight does not settle drug choice — coverage, tolerance, and indication differ.
| Head-to-head trial | SURMOUNT-5, N=751, 72 weeks |
|---|---|
| Waist reduction | -18.4 cm tirzepatide vs -13.0 cm semaglutide |
| GI discontinuation | 2.7% tirzepatide vs 5.6% semaglutide |
| Mechanism | Dual GIP/GLP-1 vs GLP-1 alone |
| Design limitation | Open-label |
| Identifiers | NCT05822830 · PMID 40353578 |
Which produces more weight loss?
Tirzepatide, in the only trial that randomised the same population to both. SURMOUNT-5 ran 72 weeks at maximum tolerated doses of each drug and found tirzepatide superior on both weight and waist circumference. Before this trial, comparisons relied on placing SURMOUNT-1 next to STEP 1 — different trials with different populations, which cannot support a superiority claim.
| Trial | Population | N | Result | Identifiers |
|---|---|---|---|---|
| SURMOUNT-5 | Adults with obesity or overweight with a weight-related comorbidity, without diabetes | 751 | Tirzepatide superior to semaglutide for weight and waist circumference at week 72 (waist -18.4 cm vs -13.0 cm) | NCT05822830 · PMID 40353578 · DOI |
| SURMOUNT-1 | Adults with obesity or overweight, without type 2 diabetes | 2,539 | Mean weight reduction up to about 20.9% at 15 mg vs 3.1% placebo | NCT04184622 · PMID 35658024 · DOI |
Does that make tirzepatide the better choice?
Not necessarily for a given person. Semaglutide has cardiovascular-outcome evidence in specific populations that tirzepatide's outcome programme has not replicated in the same form, and coverage, tolerance, injection experience, and cost all differ. A drug that is superior on one endpoint in one population is not automatically the right prescription.
The decision belongs with a prescriber who knows your comorbidities and coverage.
Is one better tolerated?
In SURMOUNT-5, fewer participants discontinued tirzepatide because of gastrointestinal effects (2.7%) than semaglutide (5.6%). Both produced gastrointestinal effects in a majority of participants at some point; the difference is in how often those effects ended treatment.
What the evidence shows
- Direct randomised evidence of greater weight and waist reduction with tirzepatide.
- Lower gastrointestinal discontinuation with tirzepatide in that trial.
- Distinct mechanisms — dual agonist versus single agonist.
What the evidence does not show
- That tirzepatide is superior on cardiovascular outcomes.
- That the result applies to people with type 2 diabetes, who were excluded.
- That compounded versions of either drug perform like the approved products.
- SURMOUNT-5 was open-label, which can influence behaviour and reporting.
- Participants had obesity without diabetes; results may not generalise.
- Both trials were manufacturer-sponsored.
Related: SURMOUNT-5 summary · Complete guide
How large is the effect across the verified trials?
| Trial arm | Point estimate | Range | N |
|---|---|---|---|
| SURMOUNT-1 · 15 mg | 20.9% | 19.5% to 22.3% | 2,539 |
| SURMOUNT-1 · 10 mg | 19.5% | 18.2% to 20.8% | 2,539 |
| SURMOUNT-1 · 5 mg | 15.0% | 13.8% to 16.2% | 2,539 |
| SURMOUNT-2 · 15 mg | 14.7% | 13.4% to 16.0% | 938 |
| SURMOUNT-2 · 10 mg | 12.8% | 11.5% to 14.1% | 938 |
| SURMOUNT-1 · placebo | 3.1% | 2.3% to 3.9% | 2,539 |
| Series | Wk 0 | Wk 12 | Wk 24 | Wk 40 | Wk 56 | Wk 72 |
|---|---|---|---|---|---|---|
| Tirzepatide 15 mg | 0% | -6.5% | -12.4% | -16.8% | -19.3% | -20.9% |
| Tirzepatide 5 mg | 0% | -5.1% | -9.3% | -12.4% | -14.2% | -15.0% |
| Placebo | 0% | -1.4% | -2.3% | -2.8% | -3.0% | -3.1% |
When was each piece of this evidence established?
| Date | Event |
|---|---|
| May 2022 | Tirzepatide approved as Mounjaro for type 2 diabetes |
| Jun 2022 | SURMOUNT-1 published in the New England Journal of Medicine |
| Jul 2023 | SURMOUNT-2 published in the Lancet |
| Nov 2023 | Tirzepatide approved as Zepbound for chronic weight management |
| Dec 2023 | SURMOUNT-4 withdrawal results published in JAMA |
| Jun 2024 | SURMOUNT-OSA published; obstructive sleep apnoea evidence established |
| May 2025 | SURMOUNT-5 head-to-head against semaglutide published in NEJM |
What does the head-to-head trial not settle?
SURMOUNT-5 randomised the same population to both drugs and followed them identically, which is the design that supports a superiority claim on the endpoints it measured. It does not settle which drug a given person should take, and reading it that way overextends a genuinely strong result.
Several considerations sit outside its scope. Semaglutide carries cardiovascular-outcome evidence in specific populations that tirzepatide's outcome programme has not replicated in the same form. Insurance coverage differs between the two and frequently determines what is actually accessible. Individual tolerability varies and cannot be predicted from group data. And the trial enrolled adults with obesity without diabetes, so its result does not transfer directly to the diabetes population.
Why were cross-trial comparisons so misleading before this trial?
Before SURMOUNT-5, comparing the two drugs meant placing SURMOUNT-1's figure next to STEP 1's — two separate trials with different populations, eligibility criteria, time periods, and protocols. Differences between trial populations routinely produce effect-size differences as large as the drug differences being investigated, which makes such comparisons close to uninformative.
This is a general lesson worth carrying beyond this comparison. Whenever two drugs are compared using numbers from separate trials, the comparison is weak regardless of how confidently it is presented, and the presentation is usually most confident in marketing material.
What does this page cover, and what does it deliberately leave out?
This page addresses Mechanism, indications, SURMOUNT-5 and safety and cost, organised around the primary question of tirzepatide vs semaglutide. Each of those elements is treated separately below rather than blended, because they carry different evidence weights and a reader is entitled to know which parts rest on randomised data and which rest on a captured commercial claim or a regulatory document.
| Element | Treatment here | Evidence basis |
|---|---|---|
| Mechanism | Covered on this page | Primary evidence |
| Indications | Covered on this page | Primary evidence |
| Surmount-5 | Covered on this page | Primary evidence |
| Safety and cost | Covered on this page | Primary evidence |
| Individualized clinical instruction | Deliberately not covered | Belongs with a prescriber who knows your history |
What are the limits of what this page can tell you?
Every page on this site rests on a specific clinical evidence, and that record has boundaries worth stating plainly rather than leaving a reader to discover them. The limitations below are specific to the material presented above.
- The evidence here describes groups, populations, or captured records — it does not describe you, and no page can substitute for a prescriber who knows your history.
- Figures carry the date on which they were verified. In a market where terms change frequently, an undated figure functions as a claim about the present that nobody has checked.
- Elements marked Verification Pending are genuinely unknown to this publication rather than merely omitted for brevity, and should not be inferred from surrounding content.
- Where a source conflicts with another, this site shows the conflict rather than resolving it, which means some questions are left open on purpose.
What would change the conclusion on this page?
Any of the following would change what this page concludes:
- New primary evidence bearing directly on tirzepatide vs semaglutide.
- A change to FDA labelling affecting any statement made above.
- A verified correction submitted through the corrections process and accepted on the evidence.
- A material change to a captured record, including a price, term, or regulatory status.
- Completion of a verification currently marked pending, which would replace a gap with a stated fact.
What do the technical terms on this page mean?
Definitions for the 10 technical terms this page uses, including DOI, GIP, GLP-1, PMID — in the specific sense used above.
| DOI | Digital Object Identifier. A persistent link to a specific published article that continues to resolve even if the journal reorganises its website. |
|---|---|
| GIP | Glucose-dependent insulinotropic polypeptide. An incretin hormone released by the small intestine after eating. Tirzepatide activates its receptor alongside the GLP-1 receptor, which is the feature that distinguishes it from single-agonist drugs such as semaglutide. |
| GLP-1 | Glucagon-like peptide-1. An incretin hormone that slows gastric emptying, signals satiety to the brain, stimulates glucose-dependent insulin release, and suppresses inappropriate glucagon secretion. |
| PMID | PubMed Identifier. A number that locates the peer-reviewed publication of a study in the PubMed database. |
| compounded | Prepared by a pharmacy rather than manufactured under an approved application. Compounded tirzepatide is not FDA approved and has not been evaluated in any randomised trial. |
| dual agonist | A drug that activates two distinct receptors. Tirzepatide is a dual GIP and GLP-1 receptor agonist, which is why describing it simply as a GLP-1 drug is imprecise. |
| endpoint | The outcome a trial is designed to measure. A primary endpoint is specified before the trial begins; secondary and exploratory endpoints carry progressively weaker inferential weight. |
| maximum tolerated dose | The highest dose an individual can take without unacceptable adverse effects. Trials frequently escalate to this point rather than to a fixed dose, which means participants in one arm may be taking different amounts. |
| open-label | A trial in which participants and investigators know which treatment is being given. SURMOUNT-5 was open-label, a genuine limitation, though weight is an objective measurement less vulnerable to expectation than a self-reported outcome. |
| placebo | An inactive comparator given so that the effect of the drug can be separated from the effect of being in a trial. Placebo groups in the SURMOUNT trials still lost some weight, which is why the placebo-subtracted difference matters more than the raw figure. |
Frequently asked questions
Which is more effective, tirzepatide or semaglutide?
In SURMOUNT-5, the only head-to-head trial, tirzepatide produced greater weight and waist reduction.
Which has fewer side effects?
Both cause gastrointestinal effects; discontinuation because of them was lower with tirzepatide in SURMOUNT-5.
Does semaglutide have advantages?
It carries cardiovascular-outcome evidence in specific populations that tirzepatide's programme has not replicated in the same form.
Can I switch between them?
That is a prescriber decision. This site does not publish switching or conversion guidance.
Change history
| Date | Change |
|---|---|
| 2026-07-22 | Page published with current dataset snapshot. |
Dates change only for substantive edits, never for cosmetic changes. Corrections: corrections policy.