Tirzepatide
Tirzepatide is a first-in-class dual GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptor agonist, marketed as Mounjaro for diabetes and Zepbound for weight management. By activating both incretin receptors simultaneously, tirzepatide produces more potent effects on appetite, glucose metabolism, and fat utilization than GLP-1-only agonists. The SURMOUNT trials demonstrated average weight loss of 20-22% of body weight — surpassing semaglutide in head-to-head comparisons. The GIP component is thought to enhance fat metabolism and may reduce the nausea commonly seen with pure GLP-1 agonists. Administered as a once-weekly subcutaneous injection.
Frequency
Once weekly, same day each week
Cycle Length
Ongoing under medical supervision. Minimum 16-20 weeks to assess full efficacy at maintenance dose.
Route
Subcutaneous
Research Level
Established
Goals
Dosing Protocol
Start at 2.5 mg weekly for 4 weeks, then 5 mg weekly for 4 weeks. Titrate in 2.5 mg increments every 4 weeks as tolerated: 7.5 mg → 10 mg → 12.5 mg → 15 mg. Compounded vials vary — with a typical 10 mg vial reconstituted in 2 mL, 5 mg = 100 units on a U-100 insulin syringe.
Timing
Any time of day, once weekly. Maintain consistent weekly schedule.
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Potential Side Effects
- Nausea (generally milder than semaglutide)
- Diarrhea
- Constipation
- Decreased appetite
- Injection site reactions
- Abdominal pain
- Muscle loss — mitigate with regular strength training and a high-protein diet
- Rare: pancreatitis
- Gallbladder issues (risk increases with rapid weight loss)
- Contraindicated with personal or family history of medullary thyroid carcinoma (MTC)
Important Warnings
- Contraindicated with personal or family history of medullary thyroid carcinoma (MTC)
- Do not use with personal history of pancreatitis
- Prioritize protein intake and resistance training to minimize muscle loss
- Not for use during pregnancy
Works Well With
Research References
- Jastreboff AM, et al. N Engl J Med. 2022;387(3):205-216. doi:10.1056/NEJMoa2206038
- Frías JP, et al. N Engl J Med. 2021;385(6):503-515. doi:10.1056/NEJMoa2107519
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Medical Disclaimer: This information is for educational purposes only and is not intended as medical advice. Tirzepatide may be regulated differently in various jurisdictions. Always consult with a qualified healthcare provider before beginning any peptide protocol. PepStack Pro does not sell peptides or provide medical advice. Content reviewed by Dr. Seth Miller, MD.