The math for this vial
- Concentration: 15 mg ÷ 2 mL = 7.5 mg/mL (7,500 mcg/mL).
- Volume of one U-100 unit: 1 ÷ 100 = 0.01 mL.
- Mass in one unit: 7,500 mcg/mL × 0.01 mL = 75 mcg.
- The whole vial is 200 U-100 units of solution, more than one 1 mL syringe holds.
On a U-40 syringe each unit is 0.025 mL, so each unit holds 2.5 times as much: 187.5 mcg at 2 mL. See U-100 vs U-40 units.
Unit chart
What common U-100 readings hold from a 15 mg vial, by water volume.
| Units | mL | 1 mL water | 2 mL water | 3 mL water |
|---|---|---|---|---|
| 1 | 0.01 | 150 mcg | 75 mcg | 50 mcg |
| 5 | 0.05 | 750 mcg | 375 mcg | 250 mcg |
| 10 | 0.1 | 1.5 mg | 750 mcg | 500 mcg |
| 20 | 0.2 | 3 mg | 1.5 mg | 1 mg |
| 25 | 0.25 | 3.75 mg | 1.875 mg | 1.25 mg |
| 50 | 0.5 | 7.5 mg | 3.75 mg | 2.5 mg |
| 100 | 1 | 15 mg | 7.5 mg | 5 mg |
About this vial size
15 mg is a mid-size Tirzepatide vial. Across the water volumes above, one U-100 unit holds between 50 mcg (at 3 mL) and 150 mcg (at 1 mL). Compared with a 10 mg vial at the same water volume, it is 1.5 times as concentrated, so the same mass takes 0.67 times the units. A 20 mg vial at the same water volume is 1.33 times as concentrated as this one.
Tirzepatide research vials run from 5 mg to 60 mg. A 60 mg vial in 2 mL is 30 mg/mL, where a single unit on a U-100 syringe holds 300 mcg. At that strength the reading precision of the syringe matters more than anything else on this page.
Storage and handling
- For the approved pens, the US prescribing information allows storage unrefrigerated (up to 30 °C) for up to 21 days; otherwise they are refrigerated and must not be frozen. That data applies to Lilly's formulation, not to reconstituted research powder.
- No validated in-use stability data exists for reconstituted research tirzepatide. Keep reconstituted vials refrigerated, protected from light, and labeled with date and concentration.
Tirzepatide is FDA-approved as Mounjaro and Zepbound. FDA ended the shortage-based compounding allowance in early 2025, and "research use only" tirzepatide is not an approved product.