What is Tirzepatide?
Tirzepatide is a “twincretin”: a dual agonist that activates both the GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) receptors at once. Eli Lilly developed it, and the FDA approved it in 2022 as Mounjaro for type 2 diabetes and in 2023 as Zepbound for obesity.
The dual mechanism is the point. GLP-1 agonists like semaglutide already produce strong weight loss. GIP receptors add a separate effect on fat-cell metabolism, insulin sensitivity and energy expenditure, so activating both with one molecule is why tirzepatide produces higher trial weight loss than any earlier obesity drug.
In the SURMOUNT trials, average weight reduction reached 20-22% at the highest dose. For context, bariatric surgery typically achieves 25-35%.
Effects, what does the research say?
Weight Loss, Clinical Trial Data
The SURMOUNT-1 trial (2022, n=2539) is the main result:
- Average weight reduction: 20.9% at 15 mg dose over 72 weeks vs 3.1% for placebo
- 91% of participants lost ≥5% body weight; 57% lost ≥20%
- Dose-dependent: 5 mg achieved 15%, 10 mg achieved 19.5%, 15 mg achieved 20.9%
- Direct comparison to semaglutide (SURPASS-2): tirzepatide showed 5-7% greater weight loss
“Tirzepatide, a dual GIP and GLP-1 receptor agonist, resulted in substantial and sustained reductions in body weight in participants with obesity, with more than half achieving 20% or greater weight loss at the highest dose.”
Jastreboff AM et al. (2022), Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine. · PMID 35658024 ↗
Semaglutide vs. Tirzepatide, Head-to-Head
The SURPASS-2 trial (2021) is the direct comparison:
- Tirzepatide at all three doses (5 mg, 10 mg, 15 mg) was superior to semaglutide 1 mg on HbA1c reduction and weight loss
- HbA1c: tirzepatide 15 mg reduced HbA1c by 2.46% vs 1.86% for semaglutide 1 mg
- Weight: tirzepatide 15 mg lost 12.4 kg vs 6.2 kg for semaglutide 1 mg
“Tirzepatide was superior to semaglutide with respect to change in HbA1c and body weight from baseline at 40 weeks in patients with type 2 diabetes.”
Frias JP et al. (2021), Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). New England Journal of Medicine. · PMID 34170647 ↗
Metabolic & Cardiovascular Benefits
Beyond weight and blood sugar, the research data shows a broad metabolic profile:
- Significant reductions in blood pressure, triglycerides and LDL cholesterol
- SURMOUNT-OSA (2024): tirzepatide reduced sleep apnoea severity by 55-63%, a benefit beyond weight loss
- SURPASS-CVOT ongoing: cardiovascular outcomes trial expected to confirm cardioprotective effects
- Reduces liver fat (NAFLD/NASH relevance), superior to semaglutide in preliminary data
Dosage, what is being researched?
Important: Tirzepatide is an approved pharmaceutical requiring medical supervision. Doses below reflect approved clinical protocols and published research.
| Indication | Starting Dose | Maintenance Dose | Escalation |
|---|---|---|---|
| T2 Diabetes (Mounjaro) | 2.5 mg/week | 5-15 mg/week | +2.5 mg every 4 weeks |
| Obesity (Zepbound) | 2.5 mg/week | 5-15 mg/week | +2.5 mg every 4 weeks |
| Research protocols | 2.5 mg/week | 5-10 mg/week | Same escalation approach |
Storage & Reconstitution
- Approved pens (Mounjaro/Zepbound): Refrigerate at 2-8°C. Can be stored at room temperature (up to 30°C) for up to 21 days.
- Research compound (lyophilised): Refrigerator (2-8°C), protected from light, up to 24 months
- After reconstitution with bacteriostatic water: max. 28 days refrigerated
- Do not freeze. Add water slowly along the glass wall, do not shake.