💊 GLP-1 Drugs
Tirzepatide vs Semaglutide — Complete 2026 Comparison
The definitive comparison of tirzepatide (Mounjaro) vs semaglutide (Ozempic/Wegovy) — weight loss, diabetes control, cardiovascular effects, side effects, and cost. Updated January 2026.
Key Takeaways
- SURMOUNT-5 trial confirmed tirzepatide produces ~47% more weight loss than semaglutide
- Tirzepatide reduces HbA1c by 2.1–2.3% vs semaglutide's 1.5–1.8%
- Semaglutide has stronger cardiovascular outcome data (SELECT trial) — tirzepatide CVD trial ongoing
- Both are once-weekly injections with similar dose escalation principles
- Tirzepatide typically costs 10–20% more than semaglutide in private market
The SURMOUNT-5 Trial — Definitive Head-to-Head
Published in 2025, SURMOUNT-5 was the head-to-head trial comparing tirzepatide 15mg against semaglutide 2.4mg (Wegovy) in people with obesity without Type 2 diabetes over 72 weeks. This provides the most rigorous comparison available.
20.2%
Tirzepatide weight loss (SURMOUNT-5)
13.7%
Semaglutide weight loss (SURMOUNT-5)
47%
More people achieved ≥25% weight loss with tirzepatide
Complete Evidence Comparison
| Outcome | Tirzepatide (Mounjaro) | Semaglutide (Wegovy/Ozempic) | Winner |
|---|---|---|---|
| Average weight loss | 20–22% | 13–17% | Tirzepatide |
| HbA1c reduction (T2D) | 2.1–2.3% | 1.5–1.8% | Tirzepatide |
| CVD outcome trial | SURMOUNT-MMO (ongoing) | SELECT: 20% CVD reduction | Semaglutide |
| Blood pressure reduction | ~8 mmHg SBP | ~6 mmHg SBP | Tirzepatide |
| LDL reduction | ~24% | ~5% | Tirzepatide |
| Liver fat reduction | More (NASH trials) | Significant | Tirzepatide |
| Tolerability | Slightly better per weight loss | Similar | Tirzepatide (slight edge) |
| Weekly injection | Yes | Yes | Tie |
| Private cost (UK/month) | £200–350 | £180–280 | Semaglutide |
When to Choose Semaglutide
- Existing cardiovascular disease: SELECT trial shows 20% CVD event reduction — the only approved drug for CVD risk reduction in non-diabetic obesity
- Cost sensitivity: Semaglutide is generally cheaper privately
- More long-term data: Semaglutide has been used longer with more real-world safety data
When to Choose Tirzepatide
- Maximum weight loss priority: Significantly more weight loss in every clinical trial
- Type 2 diabetes: More powerful glucose-lowering — better HbA1c reduction
- Previous poor response to semaglutide: Many non-responders to semaglutide respond to tirzepatide's dual GLP-1/GIP mechanism
Frequently Asked Questions
Which is better for weight loss — Mounjaro or Ozempic?▼
Tirzepatide (Mounjaro/Zepbound) consistently produces more weight loss — average 20–22% vs 15–17% for semaglutide (Ozempic/Wegovy). In the SURMOUNT-5 direct comparison, tirzepatide produced 47% more people achieving ≥25% weight loss. For maximum weight loss, tirzepatide is clearly superior.
Is tirzepatide safer than semaglutide?▼
Both have similar safety profiles in clinical trials. Tirzepatide has slightly better GI tolerability relative to the greater weight loss produced. Serious side effect rates (pancreatitis, thyroid concerns) are comparable. Semaglutide has more long-term real-world safety data accumulated. Neither has raised concerning safety signals in large-scale monitoring.
Can you switch between tirzepatide and semaglutide?▼
Yes — switching is straightforward. When switching from semaglutide to tirzepatide (for better efficacy), start tirzepatide at 2.5mg at the next injection time point. When switching from tirzepatide to semaglutide, start at 0.25mg. No washout period is required — both are weekly injections with manageable transitions.
Related Health Guides
Article
Mounjaro vs Ozempic — Full Guide
Article
Wegovy Complete Guide
Article
Retatrutide — Next Generation Drug
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⚕️ Medical Disclaimer: For informational purposes only. Always consult a qualified healthcare professional before starting or changing any medication or treatment.
PS
Consultant Endocrinologist
All articles reviewed by qualified healthcare professionals following NHS, AHA, and WHO guidelines.