Tirzepatide
Tirzepatide is a dual GIP and GLP-1 receptor agonist approved as Mounjaro (type 2 diabetes) and Zepbound (weight management). It produced greater average weight loss than semaglutide in head-to-head trials — roughly 20% at the highest dose over 72 weeks.
What it is
Tirzepatide activates two incretin receptors instead of one. The GIP component appears to reduce nausea and improve fat metabolism relative to GLP-1 agonism alone. It is injected once weekly. Research-grade tirzepatide is sold lyophilized and reconstituted before use.
What the research says
Key findings:
- SURMOUNT-1: 20.9% mean weight loss at 15 mg over 72 weeks vs 3.1% placebo (PMID 35658024)
- SURMOUNT-5 head-to-head: tirzepatide 20.2% vs semaglutide 13.7% weight loss at 72 weeks (PMID 40353578)
- SURPASS-2: superior HbA1c reduction vs semaglutide 1 mg in type 2 diabetes (PMID 34170647)
- Reduced obstructive sleep apnea severity in the SURMOUNT-OSA trial (PMID 38912654)
Clinical titration schedule (Zepbound label)
| Weeks | Weekly dose |
|---|---|
| 1–4 | 2.5 mg |
| 5–8 | 5 mg |
| 9–12 | 7.5 mg |
| 13–16 | 10 mg |
| 17–20 | 12.5 mg |
| 21+ | 15 mg (max) |
Many people stop titrating at 5–10 mg if results are adequate; the label allows holding at any step.
Reconstitution tables
10mg vial
| Bacteriostatic water | Concentration | Units for 2.5 mg | Units for 5 mg | Units for 7.5 mg | Units for 10 mg |
|---|---|---|---|---|---|
| 1 ml | 10 mg/ml | 25 | 50 | 75 | 100 |
| 2 ml | 5 mg/ml | 50 | 100 | exceeds 1 ml | exceeds 1 ml |
15mg vial
| Bacteriostatic water | Concentration | Units for 2.5 mg | Units for 5 mg | Units for 10 mg | Units for 15 mg |
|---|---|---|---|---|---|
| 1.5 ml | 10 mg/ml | 25 | 50 | 100 | exceeds 1 ml |
| 1 ml | 15 mg/ml | 16.7 | 33 | 67 | 100 |
Storage
- Refrigerate powder and reconstituted solution; use reconstituted solution within 28 days; protect from light.
Common stacks
- Tirzepatide is usually run alone. Combining with other GLP-1 compounds is not supported by any data and raises additive GI and hypoglycemia risk.
- Retatrutide vs Tirzepatide.
Side effects reported
Nausea, diarrhea, decreased appetite, constipation, and injection-site reactions. Same boxed warning as semaglutide for thyroid C-cell tumors in rodents. Hypoglycemia risk is higher when combined with insulin or sulfonylureas.
Video explanation
Third-party educational video. Not affiliated with PepIQ.
Frequently asked questions
How many units is 2.5 mg of tirzepatide?
At 10 mg/ml, 25 units. At 5 mg/ml, 50 units.
Tirzepatide vs semaglutide — which is stronger?
Tirzepatide produced more weight loss in the direct comparison trial (about 20% vs 14%).
How long does a 10mg vial last?
Four weeks at 2.5 mg; two weeks at 5 mg; one dose at 10 mg.
Why is nausea often milder than with semaglutide?
The GIP component is thought to blunt GI side effects; trial dropout rates for GI reasons were lower.
Can I reconstitute a 15mg vial with 1 ml?
Yes; it gives 15 mg/ml, which keeps even the 15 mg dose within a 1 ml syringe.
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