Zepbound and Wegovy are injectable medications approved for chronic weight management that contain different active molecules and target different receptors. At Longevity Benchmark, we evaluate prescription metabolic options against published trial evidence rather than manufacturer marketing. While both medications require once-weekly subcutaneous injection, their clinical trial records show distinct results for weight reduction, glycemic control, and cardiovascular endpoints.
When comparing zepbound vs wegovy, the primary published head-to-head evidence comes from the SURMOUNT-5 trial in adults with obesity without diabetes. In that trial, tirzepatide produced greater average weight reduction than semaglutide over 72 weeks of treatment. Deciding between them involves reviewing published trial outcomes, documented adverse event patterns, and label warnings alongside a licensed medical provider.
The Verdict
Zepbound (tirzepatide) vs Wegovy (semaglutide), Side by Side
| Attribute | Zepbound (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Active molecule | Tirzepatide | Semaglutide |
| Receptor target | Dual GIP and GLP-1 receptor agonist | GLP-1 receptor agonist |
| Manufacturer | Eli Lilly | Novo Nordisk |
| Approved use category | Chronic weight management | Chronic weight management |
| Head-to-head weight result (SURMOUNT-5) | Least-squares mean weight change of -20.2% over 72 weeks | Least-squares mean weight change of -13.7% over 72 weeks |
| Placebo-controlled weight result | Mean weight change of -15.0% (5 mg), -19.5% (10 mg), and -20.9% (15 mg) over 72 weeks in SURMOUNT-1 | Mean weight change of -14.9% (2.4 mg) over 68 weeks in STEP 1 |
| Published cardiovascular outcomes trial | No equivalent published trial available | Primary cardiovascular endpoint occurred in 6.5% vs 8.0% placebo in SELECT (hazard ratio 0.80) |
| Most common adverse events | Gastrointestinal events (nausea, diarrhea, vomiting), primarily during dose escalation | Gastrointestinal events (nausea, diarrhea, vomiting), primarily during dose escalation |
| Administration method | Once-weekly subcutaneous injection | Once-weekly subcutaneous injection |
| Boxed warning | Thyroid C-cell tumours observed in rodents | Thyroid C-cell tumours observed in rodents |
What Separates the Two Brands
Zepbound and Wegovy are distinct pharmaceutical formulations approved for the single therapeutic category of chronic weight management. Zepbound contains tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist manufactured by Eli Lilly. In contrast, Wegovy contains semaglutide, a GLP-1 receptor agonist manufactured by Novo Nordisk.
Both medications are administered once weekly through subcutaneous injection and share the same regulatory classification for chronic weight management. Each manufacturer sells the same molecule under a separate brand name for type 2 diabetes: Mounjaro for tirzepatide and Ozempic for semaglutide. The official prescribing information for each product carries a boxed warning concerning thyroid C-cell tumours identified in rodent studies.
- Active Molecule. Zepbound delivers tirzepatide, while Wegovy delivers semaglutide.
- Receptor Targets. Zepbound targets both GIP and GLP-1 receptors, whereas Wegovy targets GLP-1 receptors alone.
- Manufacturing Origin. Eli Lilly manufactures Zepbound, and Novo Nordisk manufactures Wegovy.
- Approved Category. Both products share the approved category of chronic weight management in the United States.
Zepbound vs Wegovy in the SURMOUNT-5 Trial
The SURMOUNT-5 clinical trial provides the only published direct head-to-head comparison between tirzepatide and semaglutide for chronic weight management. Published in 2025, this phase 3b, open-label trial enrolled 751 adults with obesity who did not have type 2 diabetes. Participants were randomised in a 1:1 ratio to receive the maximum tolerated dose of tirzepatide (10 mg or 15 mg) or semaglutide (1.7 mg or 2.4 mg) once weekly for 72 weeks.
Tirzepatide met the primary end point by demonstrating a statistically superior percentage change in body weight at week 72. Least-squares mean weight change was -20.2% (95% CI -21.4 to -19.1) with tirzepatide compared to -13.7% (95% CI -14.9 to -12.6) with semaglutide, representing a statistically significant difference (P<0.001). Waist circumference reductions also differed between the two arms, reaching -18.4 cm with tirzepatide versus -13.0 cm with semaglutide (P<0.001).
Categorical weight reduction thresholds in SURMOUNT-5 favored tirzepatide across all evaluated markers. Participants receiving tirzepatide were more likely to achieve weight reductions of at least 10%, 15%, 20%, and 25% at week 72. This head-to-head trial was funded by Eli Lilly and utilised an open-label design, meaning both investigators and participants knew which drug was administered.
- Trial Design. SURMOUNT-5 was a phase 3b, open-label trial comparing 751 adults without type 2 diabetes over 72 weeks.
- Primary End Point. Least-squares mean weight reduction reached -20.2% on tirzepatide versus -13.7% on semaglutide (P<0.001).
- Waist Circumference. Tirzepatide produced an average waist reduction of -18.4 cm compared to -13.0 cm for semaglutide (P<0.001).
- Funding Source. Eli Lilly funded the trial, which compared the maximum tolerated doses of both medications.
Comparing Zepbound vs Wegovy Across Placebo Trials
Placebo-controlled registration trials established the independent efficacy of both molecules before head-to-head data became available. In the SURMOUNT-1 trial, investigators evaluated tirzepatide in 2,539 adults with a BMI of 30 or greater, or 27 or greater with a weight-related complication, excluding individuals with diabetes. Across 72 weeks of double-blind treatment, mean weight change was -15.0% for 5 mg, -19.5% for 10 mg, and -20.9% for 15 mg, compared to -3.1% in the placebo group.
Categorical response rates in SURMOUNT-1 demonstrated that 85%, 89%, and 91% of participants across the 5 mg, 10 mg, and 15 mg arms achieved at least 5% weight loss, compared to 35% on placebo. Reductions of 20% or greater were documented in 50% of the 10 mg group and 57% of the 15 mg group, versus 3% on placebo. The trial cohort had a mean baseline weight of 104.8 kg and a mean BMI of 38.0, with funding provided by Eli Lilly.
For semaglutide, the double-blind STEP 1 trial examined 1,961 adults with a BMI of 30 or greater, or 27 or greater with a weight-related coexisting condition, without diabetes. Over 68 weeks alongside lifestyle intervention, semaglutide 2.4 mg produced a mean weight change of -14.9% compared to -2.4% for placebo, reflecting a treatment difference of -12.4 percentage points (95% CI -13.4 to -11.5, P<0.001) and an absolute reduction of -15.3 kg versus -2.6 kg. Reaching a 5% or greater reduction occurred in 86.4% of semaglutide participants versus 31.5% on placebo, with funding provided by Novo Nordisk.
- SURMOUNT-1 Thresholds. In SURMOUNT-1, weight loss of 20% or more occurred in 50% of the 10 mg arm and 57% of the 15 mg arm, compared to 3% on placebo.
- STEP 1 Thresholds. In STEP 1, weight loss of 10% or more was reached by 69.1% of semaglutide participants, and 15% or more by 50.5%, compared to 12.0% and 4.9% on placebo.
- Cross-Trial Limits. Direct comparisons between SURMOUNT-1 and STEP 1 remain limited by different trial durations, study populations, and protocol-specified lifestyle programs.
Glycemic and Weight Outcomes in SURPASS-2
The SURPASS-2 clinical trial measured glycemic and weight differences between tirzepatide and semaglutide in patients with type 2 diabetes. This open-label, 40-week trial enrolled 1,879 patients with a mean baseline HbA1c of 8.28%, a mean age of 56.6 years, and a mean baseline weight of 93.7 kg. Investigators evaluated three weekly doses of tirzepatide (5 mg, 10 mg, and 15 mg) directly against a 1 mg weekly dose of semaglutide.
Mean reductions in HbA1c were -2.01, -2.24, and -2.30 percentage points across the tirzepatide 5 mg, 10 mg, and 15 mg groups, compared to -1.86 percentage points with semaglutide 1 mg. The treatment differences versus semaglutide were -0.15 percentage points (95% CI -0.28 to -0.03, P=0.02) for 5 mg, -0.39 percentage points (95% CI -0.51 to -0.26, P<0.001) for 10 mg, and -0.45 percentage points (95% CI -0.57 to -0.32, P<0.001) for 15 mg. Hypoglycemia with blood glucose below 54 mg/dL occurred in 0.6% (5 mg), 0.2% (10 mg), and 1.7% (15 mg) of tirzepatide patients, compared to 0.4% with semaglutide 1 mg.
Secondary weight outcomes in SURPASS-2 also showed statistically significant treatment differences favoring tirzepatide. Reductions exceeded semaglutide 1 mg by -1.9 kg for 5 mg, -3.6 kg for 10 mg, and -5.5 kg for 15 mg, with P<0.001 across all three comparisons. Eli Lilly funded SURPASS-2, which evaluated these molecules under diabetes-focused trial parameters rather than weight-management dosing protocols. Readers interested in glycemic markers can explore our reviews of A1c vs fasting glucose and fasting insulin.
- Patient Population. SURPASS-2 enrolled 1,879 adults with type 2 diabetes with a mean baseline HbA1c of 8.28% over 40 weeks.
- Glycemic Separation. Tirzepatide lowered HbA1c by -2.01 to -2.30 percentage points, compared to -1.86 percentage points for semaglutide 1 mg.
- Weight Divergence. Tirzepatide produced additional weight reductions of -1.9 kg, -3.6 kg, and -5.5 kg relative to semaglutide 1 mg (P<0.001).
- Dosing Context. Semaglutide was tested at a 1 mg weekly dose in SURPASS-2, which is lower than the 2.4 mg arm used in STEP 1 and SELECT.
Cardiovascular Evidence in the SELECT Trial
Long-term cardiovascular outcomes have been formally evaluated for semaglutide in patients without diabetes, while equivalent trial data for tirzepatide has not been published. In the SELECT trial, researchers enrolled 17,604 patients aged 45 years or older with preexisting cardiovascular disease and a BMI of 27 or greater without diabetes. Participants received weekly semaglutide 2.4 mg or placebo over a mean follow-up period of 39.8 months.
The primary composite cardiovascular end point occurred in 6.5% of patients in the semaglutide group compared to 8.0% in the placebo group. This yielded a hazard ratio of 0.80 (95% CI 0.72 to 0.90, P<0.001) in favor of semaglutide. Adverse events leading to permanent treatment discontinuation occurred in 16.6% of participants assigned to semaglutide versus 8.2% assigned to placebo (P<0.001).
Novo Nordisk funded SELECT. An equivalent published cardiovascular outcomes trial for tirzepatide is not available, meaning direct comparison between the two molecules on cardiovascular event endpoints cannot be made on equal empirical terms. Readers evaluating metabolic risk factors can review our overview of visceral fat and its relationship to vascular health.
Trial Safety Profiles and Tolerability Patterns
Across all major clinical trials for both medications, gastrointestinal events constituted the most commonly reported adverse reactions. In trial reports, these events were characterized as mostly mild to moderate in severity and appeared primarily during the dose-escalation phases.
In the open-label SURPASS-2 trial, nausea was reported in 17% to 22% of participants receiving tirzepatide across doses and in 18% of those receiving semaglutide 1 mg. Diarrhea occurred in 13% to 16% of tirzepatide patients and 12% of semaglutide patients, while vomiting was documented in 6% to 10% and 8%, respectively. Serious adverse events were reported in 5% to 7% of tirzepatide patients across doses compared to 3% of semaglutide patients.
Treatment discontinuation rates due to adverse events show consistent patterns across placebo-controlled programs. In STEP 1, 4.5% of semaglutide 2.4 mg participants discontinued treatment because of gastrointestinal events, compared to 0.8% in the placebo group. In SURMOUNT-1, adverse events led to discontinuation in 4.3% of the 5 mg group, 7.1% of the 10 mg group, 6.2% of the 15 mg group, and 2.6% of the placebo group. The approved prescribing information for both drugs carries a boxed warning about thyroid C-cell tumours observed in rodents. Nutritional support during therapy is discussed in our guide on nutrient-dense foods on GLP-1.
- Gastrointestinal Frequency. Nausea affected 17% to 22% on tirzepatide and 18% on semaglutide 1 mg in SURPASS-2.
- Discontinuation in STEP 1. Gastrointestinal adverse events caused 4.5% of semaglutide participants to stop treatment, versus 0.8% on placebo.
- Discontinuation in SURMOUNT-1. Adverse events led to permanent cessation in 4.3% to 7.1% of tirzepatide participants, compared to 2.6% on placebo.
- Boxed Warning. Both medications carry boxed warnings in their official prescribing information regarding thyroid C-cell tumours in rodents.
Diabetes Sibling Brands and Information Limits
Both active molecules are marketed under alternative brand names that are specifically approved for the treatment of type 2 diabetes. Tirzepatide is marketed as Mounjaro by Eli Lilly, while semaglutide is marketed as Ozempic by Novo Nordisk. In addition, semaglutide is produced as an oral tablet named Rybelsus for type 2 diabetes management.
While Mounjaro and Ozempic deliver the same underlying active ingredients as Zepbound and Wegovy respectively, their approved use category remains restricted to type 2 diabetes. For readers comparing the diabetes-specific versions, our analysis of Ozempic vs Wegovy details the differences between formulations of semaglutide. A broader comparison between the two active compounds is available in our review of semaglutide vs tirzepatide.
Retail pricing, health insurance coverage rules, copay card terms, and pharmacy availability are outside what this page can verify. Similarly, specific clinical titration schedules, dose escalation timelines, and compounded product formulations are outside the scope of published registration data. Readers seeking current pricing or prescribing protocols should consult the official product prescribing information and their licensed medical provider.
- Tirzepatide Formulations. Eli Lilly markets tirzepatide as Zepbound for weight management and as Mounjaro for type 2 diabetes.
- Semaglutide Formulations. Novo Nordisk markets semaglutide as Wegovy for weight management, Ozempic for diabetes, and Rybelsus as an oral tablet.
- Delivery Format. Zepbound, Wegovy, Mounjaro, and Ozempic are all administered as once-weekly subcutaneous injections.
- Unpublished Variables. Prescription costs, insurance formulary determinations, and retail pharmacy supply cannot be confirmed on this page.
Clinical Context and Evidence Boundaries
Clear clinical boundaries separate the evidence established in clinical trials from individual patient prescribing choices. SURMOUNT-5, SURMOUNT-1 and STEP 1 all enrolled adults with obesity, so their results describe that population and no other. Readers seeking lifestyle-based metabolic management can review our analysis of insulin resistance and weight loss and strategies for navigating a weight loss plateau.
Our comparative assessment would change if new head-to-head clinical trials produce differing efficacy conclusions or if a dedicated cardiovascular outcomes trial for tirzepatide publishes its results. Until equivalent cardiovascular trial data is published for tirzepatide, the long-term vascular evidence base favors semaglutide, whereas magnitude of weight loss in head-to-head testing favors tirzepatide. Our ongoing reviews follow our documented editorial methodology.
To assess whether zepbound vs wegovy is appropriate for your personal health profile, discuss published trial data and contraindications with a board-certified physician.
- Non-Study Populations. The trials cited here enrolled adults with obesity; no trial on this page studied any other population.
- Trial Inversion Factors. Future head-to-head trials or dedicated tirzepatide cardiovascular outcome publications could alter the relative balance of evidence.
- Physician Consultation. The prescribing decision belongs to the reader and their prescriber.
Frequently Asked Questions
Is Zepbound the same as Mounjaro?
Zepbound and Mounjaro contain the exact same active molecule, tirzepatide, manufactured by Eli Lilly as a once-weekly subcutaneous injection. The difference lies in their approved indications in the United States. Zepbound is approved specifically for chronic weight management, whereas Mounjaro is approved for the treatment of type 2 diabetes. Both formulations carry identical boxed warnings in their prescribing information regarding thyroid C-cell tumours observed in animal studies. The underlying drug is identical; the approved use category printed on each brand's labelling is what differs.
Is Wegovy the same as Ozempic?
Wegovy and Ozempic contain the same active pharmaceutical ingredient, semaglutide, manufactured by Novo Nordisk as a once-weekly injectable therapy. However, they are approved for different clinical uses in the United States. Wegovy is approved for chronic weight management, while Ozempic is approved for type 2 diabetes. Both products carry a boxed warning regarding rodent thyroid C-cell tumours. In clinical trials, semaglutide has been evaluated at different dosage levels depending on the condition, such as 1 mg in the diabetes trial SURPASS-2 and 2.4 mg in the weight management trial STEP 1.
Which lost more weight in a direct comparison?
In the only published head-to-head clinical trial, tirzepatide produced greater average weight loss than semaglutide over 72 weeks. The SURMOUNT-5 trial evaluated 751 adults with obesity without diabetes, comparing the maximum tolerated doses of both medications. Tirzepatide achieved a least-squares mean weight change of -20.2% compared to -13.7% with semaglutide, reaching statistical significance with a P value below 0.001. Tirzepatide participants also demonstrated greater reductions in waist circumference and higher likelihoods of reaching categorical weight loss thresholds of 10%, 15%, 20%, and 25%.
Is Zepbound a GLP-1 drug?
Zepbound is a dual receptor agonist that targets both GLP-1 and GIP receptors. While it functions as a glucagon-like peptide-1 (GLP-1) receptor agonist, it also activates glucose-dependent insulinotropic polypeptide (GIP) receptors simultaneously. This dual agonism separates tirzepatide from semaglutide, which acts solely at the GLP-1 receptor. Zepbound therefore acts at two receptors where Wegovy acts at one. Both are administered via once-weekly subcutaneous injection for chronic weight management.
Why would someone be on Wegovy rather than Zepbound?
A patient might receive Wegovy instead of Zepbound because of individual clinical trial evidence, tolerance, or physician evaluation. Semaglutide has completed a dedicated cardiovascular outcomes study in patients with established cardiovascular disease and obesity without diabetes in the SELECT trial, where it reported a hazard ratio of 0.80 (95% CI 0.72 to 0.90, P<0.001) for the primary composite cardiovascular end point. An equivalent cardiovascular outcomes trial for tirzepatide has not yet been published. In addition, gastrointestinal tolerability, personal medical history, and clinical response vary between individuals, making the prescribing decision specific to each patient and their physician.
What were the side effects in the trials?
Gastrointestinal symptoms were the most common adverse events reported across clinical trials for both medications, occurring primarily during dose escalation and described as mostly mild to moderate. In the SURPASS-2 trial, nausea was reported in 17% to 22% of tirzepatide patients and 18% of semaglutide patients, while diarrhea occurred in 13% to 16% versus 12%, and vomiting occurred in 6% to 10% versus 8%. Discontinuation due to adverse events was documented in 4.3% to 7.1% on tirzepatide in SURMOUNT-1, and 4.5% due to gastrointestinal events on semaglutide in STEP 1. Both carry boxed warnings regarding thyroid C-cell tumours in rodents.
How much do Zepbound and Wegovy cost?
Out-of-pocket costs for Zepbound and Wegovy vary substantially and cannot be verified on this page. This page compares the two medicines on their published trial results and their approved use category, and it holds no pricing or coverage data for either one. For anything to do with what a prescription would cost, the document to read is the official prescribing information for each product with their prescribing clinician to understand expected expenses.