Tirzepatide
Reviewed by Fat Man in the Arena · Updated March 2026
Key Takeaway
Tirzepatide is a dual GIP/GLP-1 receptor agonist that has shown greater weight loss than semaglutide in head-to-head trials. It is sold under the brand names Mounjaro (diabetes) and Zepbound (weight management).
How it works
Tirzepatide activates both the GIP and GLP-1 receptors simultaneously. This dual action enhances insulin secretion, reduces glucagon, slows gastric emptying, and reduces appetite through complementary pathways that neither receptor achieves alone.
Benefits
- Average 20.9% body weight loss at highest dose (SURMOUNT-1)
- Greater weight loss than semaglutide in head-to-head trials
- Improved insulin sensitivity
- Reduced cardiovascular risk factors
- Better HbA1c reduction than semaglutide
Side effects
- Nausea
- Diarrhea
- Vomiting
- Constipation
- Abdominal pain
- Injection site reactions
- Rare: pancreatitis, gallbladder issues
Dosing protocol
Typical Dose
2.5 mg to 15 mg weekly
Frequency
Once weekly subcutaneous injection
Cycle Length
Ongoing
Start at 2.5 mg/week for 4 weeks. Titrate up in 2.5 mg increments every 4 weeks. Maximum FDA-approved dose is 15 mg/week for weight management (Zepbound).
Key research
Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)
New England Journal of Medicine (2022) — PubMed
At the 15 mg dose, participants lost 20.9% of body weight over 72 weeks. More than half of participants at the highest dose lost over 20% of their weight.
Tirzepatide vs Semaglutide for Weight Loss (SURMOUNT-5)
New England Journal of Medicine (2024) — PubMed
Tirzepatide 15 mg achieved 20.2% weight loss versus 13.7% with semaglutide 2.4 mg over 72 weeks in a direct head-to-head comparison.
FDA status
FDA Approved for: Type 2 diabetes (Mounjaro), chronic weight management (Zepbound)
Frequently asked questions
In the SURMOUNT-5 head-to-head trial, tirzepatide 15 mg achieved 20.2% weight loss compared to 13.7% with semaglutide 2.4 mg over 72 weeks. Tirzepatide produced statistically superior weight loss, though both medications showed significant results compared to placebo.
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Medical Disclaimer: This content is for informational and educational purposes only. It is not intended as medical advice or a substitute for professional medical consultation, diagnosis, or treatment. Always consult a qualified healthcare provider before starting any peptide protocol.