Direct trials found greater average weight and blood-glucose reductions with tirzepatide at the formulations tested. Receptor biology, available products, approved uses, cardiovascular outcomes and tolerability add context when comparing the two medicines.
Research reviewed 2026-10-14. Educational information only.
Two long-acting incretin medicines
Semaglutide and tirzepatide extend signals normally associated with eating. Semaglutide activates the receptor for glucagon-like peptide-1, or GLP-1. Tirzepatide activates both that receptor and the receptor for glucose-dependent insulinotropic polypeptide, or GIP. Both can enhance glucose-dependent insulin secretion and reduce food intake. Their shared GLP-1 activity helps explain the overlap in benefits and gastrointestinal effects; the additional GIP activity distinguishes tirzepatide’s pharmacology.
Their development programmes also addressed the short persistence of natural peptide hormones. Semaglutide combines protective sequence changes with a fatty-acid attachment that promotes albumin binding. Tirzepatide is a modified, fatty-acid-linked peptide developed from a GIP-based sequence. Albumin is an abundant blood protein that helps prolong exposure to both molecules. Lau and colleagues’ semaglutide discovery paper and Coskun and colleagues’ tirzepatide experiments explain those designs. Receptor biology supplies a reason to test a treatment; the clinical comparisons establish the size of the measured effect.
The main differences
Which receptors are activated?
GLP-1 and GIP are hormones released in response to food. Activating their receptors can increase insulin release when blood glucose is high and influence how much a person eats. Both medicines bind albumin, a blood protein that helps them remain in circulation longer.
Semaglutide
Activates the GLP-1 receptor. Its sequence changes and fatty-acid attachment help prolong its action.
Tirzepatide
Activates both GIP and GLP-1 receptors. It is one modified peptide with activity at both receptors.
What did the direct obesity trial show?
SURMOUNT-5 randomly assigned 751 adults with obesity, or overweight with a weight-related complication, who did not have type 2 diabetes to one of the two medicines for 72 weeks. Both were injected under the skin once a week. Participants used the highest trial amount they could tolerate: 10 or 15 mg of tirzepatide, or 1.7 or 2.4 mg of semaglutide. The trial measured the percentage change in body weight; 750 participants received treatment and entered the analyses.
Semaglutide
Participants lost an estimated 13.7% of their starting body weight on average by week 72.
Tirzepatide
Participants lost an estimated 20.2% of their starting body weight on average by week 72, a greater average reduction than with semaglutide at the amounts compared.
What did the direct diabetes trial measure?
SURPASS-2 randomly assigned 1,879 adults whose type 2 diabetes was inadequately controlled by metformin to weekly injections under the skin for 40 weeks. It compared tirzepatide at 5, 10 or 15 mg with semaglutide at 1 mg. The main measurement was HbA1c, which reflects blood glucose over the preceding months.
Semaglutide
HbA1c fell by 1.86 percentage points on average after 40 weeks.
Tirzepatide
HbA1c fell by 2.01–2.30 percentage points on average across the three tirzepatide groups. Each reduction was statistically greater than the reduction with semaglutide in this trial.
What does the labeled human half-life mean?
An elimination half-life describes how long the blood concentration takes to fall by half during the measured elimination phase. It helps explain persistence, but does not tell us that one medicine is more potent or that oral and injected amounts are interchangeable.
Semaglutide
The product label gives an approximate elimination half-life of one week. Absorption differs between tablets and injections.
Tirzepatide
Zepbound reports approximately 5–6 days in people with overweight or obesity; Mounjaro reports approximately 5 days in people with type 2 diabetes.
Is there a randomized cardiovascular comparison between these two?
Preventing heart attacks, strokes or cardiovascular death requires trials that follow those events. The major randomized trials used different comparison treatments and populations, so they do not directly rank semaglutide against tirzepatide for cardiovascular protection.
Semaglutide
SELECT compared semaglutide with placebo in people with cardiovascular disease and overweight or obesity who did not have diabetes.
Tirzepatide
SURPASS-CVOT compared tirzepatide with dulaglutide in people with type 2 diabetes and cardiovascular disease. A newer study compared routine-care records of tirzepatide and semaglutide users, but differences in who received each medicine could have influenced its findings.
Sources
- Nicholls SJ, Pavo I, Bhatt DL, Buse JB, Del Prato S, Kahn SE, Lincoff AM, McGuire DK, Miller D, Nauck MA, Nishiyama H, Nissen SE, Sattar N, Weerakkody G, Wiese RJ, Zinman B, Zoungas S, Basile J, Davies MJ, Giorgino F, Kellerer M, Ji L, Varkonyi T, Menon V, Broder JC, Herschtal A, D'Alessio D, SURPASS-CVOT Investigators. Cardiovascular Outcomes with Tirzepatide versus Dulaglutide in Type 2 Diabetes. New England Journal of Medicine. 2025;393(24):2409–2420. DOI: 10.1056/NEJMoa2505928. PMID: 41406444.
- Al-Nusair M, Khurana S, Eysha M, Elchouemi M, Zaki IH. Cardiovascular outcomes with tirzepatide versus semaglutide in type 2 diabetes. Journal of Diabetes & Metabolic Disorders. Published online October 5, 2026;25:280. DOI: 10.1007/s40200-026-02087-z. PMID: 42840232.
SURMOUNT-5: a direct weight comparison
Aronne and colleagues’ SURMOUNT-5 trial randomized 751 adults with obesity, or overweight with at least one weight-related complication, who did not have type 2 diabetes to once-weekly subcutaneous treatment for 72 weeks. It was open label, so participants and treating teams knew the assignment. The protocol compared maximum tolerated tirzepatide of 10 or 15 mg with maximum tolerated semaglutide of 1.7 or 2.4 mg. These amounts describe the trial arms and define the comparison. Of those randomized, 750 received treatment and entered the efficacy and safety analyses.
The main analysis estimated weight change while accounting for participants who stopped their assigned medicine or used most additional obesity medicines. It applied separate rules when someone switched to the other trial medicine or underwent weight-reduction surgery; the paper calls this the modified treatment-regimen analysis. Estimated mean weight change was −20.2% with tirzepatide, with a 95% confidence interval of −21.4% to −19.1%, and −13.7% with semaglutide, with an interval of −14.9% to −12.6% (P<0.001). The estimated difference was 6.5 percentage points in tirzepatide’s favour (95% confidence interval 4.9–8.1). Gastrointestinal events predominated and were generally mild to moderate, occurring mainly during escalation. The result establishes greater average weight reduction under this protocol. It leaves individual response and other outcomes to their own assessment.
The June 2026 Wegovy label includes tablets and a higher-strength adult injection presentation. SURMOUNT-5 tested neither the tablet nor semaglutide 7.2 mg. Its conclusion therefore remains tied to the injectable exposures actually compared.
What the two direct trials actually measured
SURMOUNT-5 follows adults without diabetes for weight change over 72 weeks; SURPASS-2 follows adults with diabetes on metformin for HbA1c change over 40 weeks.
SURMOUNT-5 • weight
- 751 adults without type 2 diabetes
- Weekly injections under the skin: tirzepatide 10 or 15 mg; semaglutide 1.7 or 2.4 mg
- Body-weight change after 72 weeks
- Average weight loss was greater with tirzepatide at the tested amounts
SURPASS-2 • glucose
- 1,879 adults with type 2 diabetes on metformin
- Weekly injections under the skin: tirzepatide 5, 10 or 15 mg; semaglutide 1 mg
- Change in HbA1c, a marker of average blood glucose, after 40 weeks
- HbA1c fell more in each tirzepatide group than in the semaglutide group
SURPASS-2: a different population and endpoint
Frías and colleagues’ SURPASS-2 trial randomized 1,879 adults with type 2 diabetes inadequately controlled on metformin. This open-label, 40-week study compared subcutaneous tirzepatide 5, 10 or 15 mg once weekly with semaglutide 1 mg once weekly. Its primary endpoint was the change in glycated haemoglobin, HbA1c, which reflects blood glucose exposure over preceding months.
The reported treatment-regimen estimates included treatment discontinuation and use of rescue glucose-lowering medication. Mean HbA1c reductions were 2.01, 2.24 and 2.30 percentage points across the three tirzepatide arms and 1.86 percentage points with semaglutide. All three comparisons favoured tirzepatide statistically. The smallest estimated between-group difference was 0.15 percentage points, with a 95% confidence interval of 0.03–0.28 points in tirzepatide’s favour. The study answers a glucose-control question using the semaglutide diabetes exposure available to that protocol. Its 1 mg comparator and diabetes population explain why it should be read separately from SURMOUNT-5.
Cardiovascular evidence has its own comparators
Weight and HbA1c are consequential measurements, but cardiovascular event prevention requires follow-up of actual events. In Lincoff and colleagues’ SELECT trial, 17,604 adults with established cardiovascular disease, overweight or obesity, and no diabetes received subcutaneous semaglutide 2.4 mg or placebo. Over a mean 39.8 months, cardiovascular death, nonfatal myocardial infarction or nonfatal stroke occurred in 6.5% and 8.0%, respectively: hazard ratio 0.80, 95% confidence interval 0.72–0.90. The observed absolute difference was 1.5 percentage points in this high-risk population.
Nicholls and colleagues’ SURPASS-CVOT compared weekly subcutaneous tirzepatide with weekly subcutaneous dulaglutide in adults with type 2 diabetes and atherosclerotic cardiovascular disease. After eligibility exclusions, the analysis included 13,165 participants. The current Mounjaro label reports median follow-up of 210.1 weeks for the programme. Tirzepatide met the prespecified noninferiority criterion for cardiovascular death, myocardial infarction or stroke; the trial did not show a statistically significant advantage over dulaglutide (hazard ratio 0.92; 95.3% confidence interval 0.83–1.01; P=0.09 for superiority). SELECT’s placebo comparison and SURPASS-CVOT’s active comparison cannot provide a randomized cardiovascular ranking between semaglutide and tirzepatide.
A new retrospective analysis by Al-Nusair and colleagues, published online October 5, 2026, directly compared records of people with type 2 diabetes using the two medicines. The investigators matched people with similar recorded characteristics to reduce differences between treatment groups, and reported fewer cardiovascular events and deaths with tirzepatide. Other differences in who received each medicine, including characteristics absent from the records and uncertainty about actual treatment exposure, could still have influenced the result. Its composite also included acute heart failure. This is useful comparative observational evidence with a different design and endpoint from a randomized cardiovascular trial.
Approved uses and exposure depend on the product
The same active ingredient can appear in products with different indications. Current US Wegovy labeling separates adult tablet uses from injection uses: the injection includes adolescent obesity and adult MASH, an inflammatory form of metabolic fatty liver disease, with moderate or advanced scarring (F2–F3) but no cirrhosis, with the liver indication under accelerated approval. Zepbound labeling covers adult weight management and moderate-to-severe obstructive sleep apnea in adults with obesity. The August 2026 Mounjaro label covers type 2 diabetes from age ten and cardiovascular risk reduction in high-risk adults with type 2 diabetes. Each indication has a defined population. Wegovy, Zepbound and Mounjaro provide the current product-level details.
The Wegovy label describes semaglutide’s elimination half-life as approximately one week. Zepbound reports approximately five to six days in people with overweight or obesity, including obesity with sleep apnea; Mounjaro describes approximately five days in type 2 diabetes. These estimates characterize persistence after absorption in their stated settings. They supply no potency conversion between molecules. Oral semaglutide also has formulation-dependent absorption, so oral and injected milligram amounts cannot be interpreted as interchangeable exposure.
Tolerability changes the practical meaning of benefit
Both medicines commonly cause nausea, vomiting, diarrhea and other digestive symptoms. Their labels also identify pancreatitis, gallbladder disease, kidney injury associated with volume depletion, serious hypersensitivity and severe gastrointestinal reactions. Glucose lowering can increase hypoglycemia risk when combined with insulin or an insulin secretagogue. Retinopathy history and the pace of glucose improvement matter in diabetes, while delayed gastric emptying has implications for oral medicines and anesthesia. The Wegovy and Zepbound labels describe these issues within each product’s evidence.
Both carry boxed warnings about thyroid C-cell tumours in rodents, with uncertain relevance to humans, and contraindications involving medullary thyroid carcinoma or MEN2 and serious hypersensitivity. Pregnancy and reproductive considerations require product-specific interpretation. Tirzepatide has a particular labeled interaction with oral hormonal contraception around treatment initiation and escalation. A simple “better tolerated” label would obscure these different clinical circumstances. Event percentages from separate trials also reflect different populations, follow-up and ascertainment, making the direct trial and the complete prescribing information more useful than a side-by-side collection of unrelated adverse-event rates.
The comparison continues after initial weight loss
Withdrawal studies show why a single end-of-treatment percentage is incomplete. The STEP 1 extension reported by Wilding and colleagues followed 327 selected participants after semaglutide or placebo and structured lifestyle support stopped at week 68. Over the next year, the former semaglutide group regained 11.6 percentage points after losing 17.3% in that subset. Both medication and structured support ended together.
Aronne and colleagues’ SURMOUNT-4 used a different withdrawal design: after a 36-week open-label tirzepatide lead-in, 670 adults without diabetes were randomized to continuation or placebo for another 52 weeks. Weight changed by −5.5% with continuation and +14.0% after withdrawal, relative to week 36. Participants reaching randomization had already tolerated the lead-in. The two studies support attention to maintenance and persistence, while their different selection and withdrawal conditions prevent a comparison of which medicine causes more regain.
What the comparison can support
The clearest comparative conclusions come from matching the question to the trial. SURMOUNT-5 supports a weight-reduction comparison in adults without diabetes at the studied tolerated injectable exposures. SURPASS-2 supports a glucose-control comparison in adults with type 2 diabetes on metformin using its specified comparator. Cardiovascular outcomes, approved indications, tolerability and long-term continuation add information that those two endpoints cannot supply.
For an individual treatment decision, the relevant outcome may be sustained glucose control, weight reduction or a complication linked to the person’s existing disease. The evidence is most informative when the formulation, population, comparator and duration stay beside the result. The accompanying profiles develop each medicine’s wider programme and provide the disease-specific trials behind those distinctions.
Frequently asked questions
Does SURMOUNT-5 compare every current semaglutide formulation?
It compared once-weekly injected semaglutide at 1.7 or 2.4 mg with the studied tirzepatide strategy. Oral semaglutide and the current higher-strength semaglutide injection require their own comparisons.
Can receptor counts predict the size of the benefit?
Receptor activity explains pharmacological differences, while human trials measure the integrated effect of exposure, biology and tolerability. Two receptor targets do not define a numerical potency ratio.
Do the withdrawal results identify a better maintenance medicine?
The STEP 1 extension and SURMOUNT-4 both observed regain after withdrawal. Their lead-ins, participant selection and changes in lifestyle support differed, so the amounts regained are separate study results.
Profiles and related reading
References
- Lau J, Bloch P, Schäffer L, Pettersson I, Spetzler J, Kofoed J, Madsen K, Knudsen LB, McGuire J, Steensgaard DB, Strauss HM, Gram DX, Knudsen SM, Nielsen FS, Thygesen P, Reedtz-Runge S, Kruse T. Discovery of the Once-Weekly Glucagon-Like Peptide-1 (GLP-1) Analogue Semaglutide. Journal of medicinal chemistry. 2015;58(18):7370–7380. DOI: 10.1021/acs.jmedchem.5b00726. PMID: 26308095.
Original ACS publisher abstract and PubMed bibliographic record read on 2026-10-14; supporting information not acquired. Abstract: sequence modifications, albumin affinity and selection of semaglutide.
- Coskun T, Sloop KW, Loghin C, Alsina-Fernandez J, Urva S, Bokvist KB, Cui X, Briere DA, Cabrera O, Roell WC, Kuchibhotla U, Moyers JS, Benson CT, Gimeno RE, D'Alessio DA, Haupt A. LY3298176, a novel dual GIP and GLP-1 receptor agonist for the treatment of type 2 diabetes mellitus: From discovery to clinical proof of concept. Molecular metabolism. 2018;18:3–14. DOI: 10.1016/j.molmet.2018.09.009. PMID: 30473097.
Original open-access article indexed at PMC6308032 and original PubMed abstract checked on 2026-10-14. Abstract and discovery experiments: recombinant receptor signaling, mouse studies and phase 1 proof of concept.
- Aronne LJ, Horn DB, le Roux CW, Ho W, Falcon BL, Gomez Valderas E, Das S, Lee CJ, Glass LC, Senyucel C, Dunn JP, SURMOUNT-5 Trial Investigators. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine. 2025;393(1):26–36. DOI: 10.1056/NEJMoa2416394. PMID: 40353578.
Original PubMed/NEJM indexed abstract and original article PDF reprint opened and read on 2026-10-14. Publisher body returned 403; the complete 11-page original report was acquired from an independent educational host. Supplements not acquired. Original report pages 27–29: eligibility, 750 treated/751 randomized, maximum tolerated subcutaneous exposures and modified treatment-regimen estimand with switching/surgical exceptions; pages 29–30 Results and safety. Reprint URL recorded in source-check.md.
- Frías JP, Davies MJ, Rosenstock J, Pérez Manghi FC, Fernández Landó L, Bergman BK, Liu B, Cui X, Brown K; SURPASS-2 Investigators. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine. 2021;385(6):503–515. DOI: 10.1056/NEJMoa2107519. PMID: 34170647.
Original indexed PubMed abstract and original indexed NEJM Methods/Results/Figure 1 read on 2026-10-14. Direct publisher body returned 403; supplements not acquired. Original Methods and Figure 1: 1,879 randomized adults on metformin, 40 weeks, treatment-regimen estimand including discontinuation/rescue medication; reported HbA1c changes.
- Lincoff AM, Brown-Frandsen K, Colhoun HM, Deanfield J, Emerson SS, Esbjerg S, Hardt-Lindberg S, Hovingh GK, Kahn SE, Kushner RF, Lingvay I, Oral TK, Michelsen MM, Plutzky J, Tornøe CW, Ryan DH, SELECT Trial Investigators. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. New England Journal of Medicine. 2023;389(24):2221–2232. DOI: 10.1056/NEJMoa2307563. PMID: 37952131.
Original PubMed abstract opened and read on 2026-10-14. Abstract Methods and Results: 17,604 adults with cardiovascular disease, BMI ≥27 and no diabetes; subcutaneous semaglutide 2.4 mg versus placebo; mean follow-up 39.8 months; three-component cardiovascular endpoint.
- Nicholls SJ, Pavo I, Bhatt DL, Buse JB, Del Prato S, Kahn SE, Lincoff AM, McGuire DK, Miller D, Nauck MA, Nishiyama H, Nissen SE, Sattar N, Weerakkody G, Wiese RJ, Zinman B, Zoungas S, Basile J, Davies MJ, Giorgino F, Kellerer M, Ji L, Varkonyi T, Menon V, Broder JC, Herschtal A, D'Alessio D, SURPASS-CVOT Investigators. Cardiovascular Outcomes with Tirzepatide versus Dulaglutide in Type 2 Diabetes. New England Journal of Medicine. 2025;393(24):2409–2420. DOI: 10.1056/NEJMoa2505928. PMID: 41406444.
Original indexed NEJM abstract and original indexed PubMed record read on 2026-10-14; full trial body not acquired. Abstract: 13,299 randomized, 13,165 modified intention-to-treat; cardiovascular death, myocardial infarction or stroke; tirzepatide versus dulaglutide; HR 0.92 (95.3% CI 0.83–1.01), P=0.003 noninferiority, P=0.09 superiority.
- Al-Nusair M, Khurana S, Eysha M, Elchouemi M, Zaki IH. Cardiovascular outcomes with tirzepatide versus semaglutide in type 2 diabetes. Journal of Diabetes & Metabolic Disorders. Published online October 5, 2026;25:280. DOI: 10.1007/s40200-026-02087-z. PMID: 42840232.
Original publisher record opened and original indexed PubMed abstract read on 2026-10-14. Full methods and supplement were not acquired; numerical HR/CI inconsistency in indexed abstract is retained as an extraction limit, so no estimate is quoted. Abstract Methods: TriNetX retrospective data, May 13, 2022–August 11, 2026; 1:1 propensity matching; cardiovascular composite includes acute heart failure.
- Novo Nordisk. WEGOVY (semaglutide) injection and tablets: US prescribing information. Revised June 2026. DailyMed.
Official DailyMed manufacturer prescribing information opened on 2026-10-14; revision June 2026. Sections 1, 2.2, 3, 4–5, 8 and 12.1–12.3; adult Wegovy HD context and formulation-specific indications.
- Eli Lilly and Company. ZEPBOUND (tirzepatide) injection: US prescribing information. Revised August 2026; DailyMed updated August 28, 2026.
Official DailyMed manufacturer prescribing information opened on 2026-10-14; revision August 2026. Sections 1, 4–5, 7–8 and 12.1–12.3; half-life 5–6 days in overweight/obesity and OSA with obesity.
- Eli Lilly and Company. MOUNJARO (tirzepatide) injection: US prescribing information. Revised August 2026; DailyMed updated August 27, 2026.
Official DailyMed manufacturer prescribing information opened on 2026-10-14; revision August 2026. Sections 1, 4–5 and 12.3; adult cardiovascular indication added August 2026; approximate 5-day half-life in type 2 diabetes.
- Wilding JPH, Batterham RL, Davies M, Van Gaal LF, Kandler K, Konakli K, Lingvay I, McGowan BM, Oral TK, Rosenstock J, Wadden TA, Wharton S, Yokote K, Kushner RF, STEP 1 Study Group. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, obesity & metabolism. 2022;24(8):1553–1564. DOI: 10.1111/dom.14725. PMID: 35441470.
Original open-access STEP 1 extension indexed at PMC9542252 and original indexed abstract read on 2026-10-14. Methods and Results: 327 extension participants; both trial product and structured lifestyle intervention stopped at week 68; follow-up to week 120.
- Aronne LJ, Sattar N, Horn DB, Bays HE, Wharton S, Lin WY, Ahmad NN, Zhang S, Liao R, Bunck MC, Jouravskaya I, Murphy MA; SURMOUNT-4 Investigators. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA. 2024;331(1):38–48. DOI: 10.1001/jama.2023.24945. PMID: 38078870.
Original indexed PubMed abstract and original PMC Table 2/Results read on 2026-10-14; supplements not acquired. 36-week open-label lead-in; 670 randomized; week 36–88 treatment-regimen weight change −5.5% continuation versus +14.0% placebo withdrawal.