| Dimension | Semaglutide | Tirzepatide |
|---|---|---|
| Class | GLP-1 receptor agonist | GLP-1 / GIP agonist |
| Category | GLP-1 | GLP-1 |
| Common vial sizes | 2.5 / 5 / 10 mg | 5 / 10 / 15 mg |
| Typical dose range | 250 mcg – 2.4 mg | 2.5 mg – 15 mg |
| Half-life | ~7 days | ~5 days |
| Status | FDA-approved formulation exists | FDA-approved formulation exists |
Educational reference only. Not medical advice — follow the instructions from your clinician or pharmacy.
Single vs dual receptor agonist
Semaglutide is a GLP-1 receptor agonist; tirzepatide is a dual GLP-1/GIP agonist. That mechanistic difference is why their dose ranges and titration schedules are not interchangeable — you cannot map a semaglutide dose onto tirzepatide one-to-one.
For the calculator, what matters is that the two use different milligram ranges, so the concentration you reconstitute to and the units you draw will look different even at the same BAC water volume.
- Semaglutide: GLP-1 only
- Tirzepatide: GLP-1 + GIP (dual)
- Different dose ladders — do not convert one to the other
What this means for reconstitution
Tirzepatide doses run in larger milligram numbers than semaglutide, so the bacteriostatic water volume you choose has a bigger effect on the draw. Semaglutide's smaller microgram-to-low-milligram doses tend to produce smaller draws at the same concentration.
Calculate each compound on its own page using your actual vial size and water volume — the comparison table above shows where they differ, but only your real numbers give the correct syringe units.