Tirzepatide vs Semaglutide: Complete Comparison (2026 Data)
Tirzepatide and semaglutide are the two most widely prescribed GLP-1 class drugs for weight loss and type 2 diabetes. Tirzepatide (sold as Mounjaro for diabetes and Zepbound for weight loss) is a dual GLP-1/GIP agonist. Semaglutide (sold as Ozempic for diabetes, Wegovy for weight loss, and Rybelsus as an oral formulation) is a GLP-1 agonist.
The SURMOUNT-5 head-to-head trial published in 2025 provides the definitive comparison: tirzepatide produces about 47% more weight loss than semaglutide at maximum doses.
Side-by-Side Comparison
| Tirzepatide | Semaglutide | |
|---|---|---|
| Brand names | Mounjaro (T2D), Zepbound (weight loss) | Ozempic (T2D), Wegovy (weight loss), Rybelsus (oral) |
| Manufacturer | Eli Lilly | Novo Nordisk |
| Mechanism | Dual agonist: GLP-1 + GIP | Single agonist: GLP-1 |
| Molecule type | Modified GIP peptide with GLP-1 activity | Modified GLP-1 peptide |
| Max dose | 15 mg (injection) | 2.4 mg (injection) / 50 mg (oral tablet) |
| Dosing | Once weekly (injection only) | Once weekly (injection) or once daily (oral) |
| Half-life | ~5 days | ~7 days |
| FDA approvals | T2D (2022), Weight loss (2023) | T2D (2017), Weight loss (2021), CV risk reduction (2024) |
| Oral option | No | Yes (Rybelsus, oral Wegovy) |
| CV outcomes trial | SURPASS-CVOT (ongoing) | SELECT (completed — 20% MACE reduction) |
The SURMOUNT-5 Head-to-Head Trial
SURMOUNT-5 is the landmark study that directly compares tirzepatide and semaglutide. Published in The New England Journal of Medicine in 2025, it is the first randomized, double-blind, head-to-head trial between these two drugs.
Trial Design
- Participants: 751 adults with BMI 30+ (or 27+ with weight-related comorbidity)
- Duration: 72 weeks
- Doses: Tirzepatide escalated to max 15 mg; semaglutide escalated to max 2.4 mg
- Primary endpoint: Percent change in body weight at 72 weeks
Key Results
| Outcome | Tirzepatide | Semaglutide |
|---|---|---|
| Average weight loss | -20.2% | -13.7% |
| Difference | 6.5 percentage points more | — |
| Lost at least 5% | 94% | 85% |
| Lost at least 10% | 82% | 66% |
| Lost at least 15% | 70% | 47% |
| Lost at least 20% | 55% | 28% |
| Lost at least 25% | 35% | 12% |
What This Means
Tirzepatide produced nearly 50% more relative weight loss than semaglutide. At the 20% threshold — often considered clinically transformative — nearly twice as many tirzepatide patients (55%) achieved it compared to semaglutide (28%).
The trial confirms what separate trial programs (SURMOUNT vs STEP) had suggested but could not definitively prove due to different patient populations.
Weight Loss Across All Major Trials
| Drug | Trial | Indication | Duration | Weight Loss |
|---|---|---|---|---|
| Tirzepatide 15 mg | SURMOUNT-1 | Obesity | 72 weeks | -22.5% |
| Tirzepatide | SURMOUNT-5 | Obesity (head-to-head) | 72 weeks | -20.2% |
| Tirzepatide 15 mg | SURMOUNT-2 | Obesity + T2D | 72 weeks | -14.7% |
| Semaglutide 2.4 mg | STEP 1 | Obesity | 68 weeks | -14.9% |
| Semaglutide 2.4 mg | SURMOUNT-5 | Obesity (head-to-head) | 72 weeks | -13.7% |
| Semaglutide 2.4 mg | STEP 2 | Obesity + T2D | 68 weeks | -9.6% |
| Oral semaglutide 50 mg | OASIS 1 | Obesity | 68 weeks | -15.1% |
Diabetes Management: SURPASS vs SUSTAIN
Both drugs are approved for type 2 diabetes, but tirzepatide has shown stronger glucose control.
| Outcome | Tirzepatide (SURPASS) | Semaglutide (SUSTAIN) |
|---|---|---|
| HbA1c reduction | Up to -2.58% | Up to -1.8% |
| HbA1c below 5.7% (normal) | Up to 46% | Not reported at this threshold |
| Weight loss (T2D trials) | -12.9 kg (SURPASS-1) | -6.5 kg (SUSTAIN-1) |
| Head-to-head vs semaglutide | Superior (SURPASS-2 vs Ozempic 1 mg) | — |
In SURPASS-2, tirzepatide was tested head-to-head against semaglutide 1 mg (Ozempic) for type 2 diabetes. Tirzepatide was superior on both HbA1c reduction and weight loss at all three dose levels (5, 10, 15 mg).
Side Effects and Tolerability
| Side Effect | Tirzepatide (SURMOUNT-5) | Semaglutide (SURMOUNT-5) |
|---|---|---|
| Any GI event | ~70% | ~65% |
| Nausea | 28% | 26% |
| Diarrhea | 22% | 18% |
| Vomiting | 13% | 10% |
| Constipation | 14% | 12% |
| Discontinuation (AEs) | ~5% | ~3% |
Both drugs have similar GI side effect profiles. Most side effects are mild to moderate and occur during the dose escalation period. Tirzepatide has slightly higher rates overall, consistent with its greater metabolic effect. Both drugs use a gradual dose titration schedule to minimize GI symptoms.
Hair Loss
Hair loss (alopecia) has been reported with both drugs at low rates. In SURMOUNT trials, ~5% of tirzepatide patients reported hair loss (vs ~1% placebo). In STEP trials, ~3% of semaglutide patients reported it. Hair loss with GLP-1 drugs is thought to be telogen effluvium — a temporary shedding caused by rapid weight loss rather than the drug itself.
Cost and Access
| Tirzepatide | Semaglutide | |
|---|---|---|
| Weight loss brand | Zepbound (~$1,059/mo list) | Wegovy (~$1,349/mo list) |
| Diabetes brand | Mounjaro (~$1,059/mo list) | Ozempic (~$935/mo list) |
| Oral option | None | Rybelsus (T2D), oral Wegovy (weight loss) |
| Direct pricing | LillyDirect: ~$550/mo | Varies by program |
| Insurance coverage | Growing | Broader (earlier approval + CV data) |
Oral Options
Semaglutide has a significant advantage in oral availability. Oral Wegovy (semaglutide tablets) was FDA-approved in 2025 for weight loss, making it the first oral GLP-1 specifically approved for obesity. Rybelsus (oral semaglutide) has been available for type 2 diabetes since 2019.
Tirzepatide has no oral formulation. While Eli Lilly has oral tirzepatide in development, it is still in clinical trials.
For patients who prefer to avoid injections, semaglutide currently offers the only approved oral GLP-1 option for weight loss.
Where Does Retatrutide Fit?
Retatrutide is the first triple agonist — targeting GLP-1, GIP, and glucagon receptors. In Phase 3 trials, it produced 28.7% body weight loss, the largest result for any anti-obesity medication. The addition of glucagon receptor agonism increases energy expenditure and drives liver fat reduction.
Retatrutide is not yet FDA-approved (expected 2027). For a detailed comparison with tirzepatide, see Retatrutide vs Tirzepatide.
Frequently Asked Questions
Is tirzepatide better than semaglutide?
For weight loss and glucose control, tirzepatide produces superior results — confirmed in head-to-head trials (SURMOUNT-5 and SURPASS-2). However, semaglutide has proven cardiovascular protection (SELECT trial), an oral formulation, and a longer safety track record. The best choice depends on individual medical needs.
What is the SURMOUNT-5 trial?
SURMOUNT-5 is the first randomized, double-blind head-to-head trial comparing tirzepatide (up to 15 mg) with semaglutide (up to 2.4 mg) for weight loss. Published in 2025, it showed tirzepatide produced -20.2% weight loss vs -13.7% for semaglutide at 72 weeks.
Does tirzepatide or semaglutide cause more side effects?
Both have similar GI side effect profiles (nausea, diarrhea, vomiting, constipation). Tirzepatide has slightly higher rates overall in head-to-head comparison, but discontinuation rates are similar (~5% vs ~3%). Both are generally well tolerated.
Can tirzepatide cause hair loss?
Hair loss has been reported at low rates (~5% in SURMOUNT trials vs ~1% placebo). This is thought to be telogen effluvium — temporary hair shedding caused by rapid weight loss, not a direct drug effect. Similar rates occur with semaglutide and other weight loss interventions.
Is there an oral tirzepatide?
Not yet. Eli Lilly has oral tirzepatide in clinical development, but it has not been approved. Currently, semaglutide is the only GLP-1 drug available in oral form for both diabetes (Rybelsus) and weight loss (oral Wegovy).
Which is better for type 2 diabetes — tirzepatide or semaglutide?
Tirzepatide demonstrated superior HbA1c reduction and weight loss in the SURPASS-2 head-to-head trial against semaglutide 1 mg (Ozempic). Both are effective, but tirzepatide produced greater glucose control across all dose levels.
Sources
- Frías, J.P., et al. (2025). Tirzepatide vs Semaglutide for Weight Loss (SURMOUNT-5). New England Journal of Medicine. DOI: 10.1056/NEJMoa2501113
- Jastreboff, A.M., et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine. DOI: 10.1056/NEJMoa2206038
- Wilding, J.P.H., et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine. DOI: 10.1056/NEJMoa2032183
- Frías, J.P., et al. (2021). Tirzepatide versus Semaglutide Once Weekly in Type 2 Diabetes (SURPASS-2). New England Journal of Medicine. DOI: 10.1056/NEJMoa2107519
- Lincoff, A.M., et al. (2023). Semaglutide and Cardiovascular Outcomes (SELECT). New England Journal of Medicine. DOI: 10.1056/NEJMoa2307563
Medical Disclaimer
The content on glp3.wiki is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Both tirzepatide and semaglutide are prescription medications — consult your healthcare provider to determine which is appropriate for you.
This site is not affiliated with Eli Lilly, Novo Nordisk, or any pharmaceutical manufacturer.
Sources
Related reading
Zepbound vs Wegovy: Which Weight Loss Drug Is Better?
Zepbound produced -20.2% vs Wegovy's -13.7% weight loss in the SURMOUNT-5 head-to-head trial. Full comparison of cost, side effects, and CV data.
Mounjaro vs Ozempic: Which Is Better for Weight Loss and Diabetes?
Mounjaro produced twice the weight loss of Ozempic in head-to-head trials. Practical comparison of cost, insurance, and prescribing differences.
Retatrutide vs Tirzepatide (Zepbound): Triple Agonist vs Dual Agonist
Retatrutide produces 28.7% weight loss (triple agonist) vs tirzepatide's 22.5% (dual agonist). A head-to-head trial is underway.