Quick math example
A 10 mg vial mixed with 2 mL gives 5 mg/mL. A 2.5 mg dose is 0.5 mL, which equals 50 units on a U-100 syringe.
15 mg tirzepatide vial examples
A 15 mg vial in 3 mL gives 5 mg/mL (5,000 mcg/mL). A 2.5 mg dose is 0.5 mL, which is 50 units on a U-100 syringe.
Using 1.5 mL instead gives 10 mg/mL, halving the draw to 0.25 mL (25 units) for the same 2.5 mg dose.
- 15 mg / 3 mL = 5 mg/mL → 2.5 mg = 0.5 mL = 50 units
- 15 mg / 1.5 mL = 10 mg/mL → 2.5 mg = 0.25 mL = 25 units
- A 15 mg vial yields about six 2.5 mg doses before dead-space loss
When the 15 mg tirzepatide vial is the right choice
The 15 mg vial maps neatly to maintenance doses on most titration schedules. By the time you are running 5–15 mg per week, a 5 or 10 mg vial covers fewer than a month of doses and creates more reconstitution cycles. The 15 mg vial reduces handling frequency without forcing you to mix unusually small or hard-to-draw volumes.
It is less suited to the earliest weeks. A 2.5 mg starting dose drawn from a 15 mg vial will land on roughly the same syringe markings as the same dose drawn from a 5 mg vial, but you carry a larger total amount of peptide in reserve — and once a vial is reconstituted, the beyond-use clock starts ticking regardless of how few doses you have drawn.
- Most appropriate when running 7.5–15 mg per week
- Reduces reconstitution frequency by roughly 3× vs a 5 mg vial
- Same draw math at any concentration — only the doses-remaining count changes
How the tirzepatide calculation works
Tirzepatide doses are often discussed in milligrams, while many vials and syringes require you to think in mg, mcg, mL, and units at the same time.
The calculator normalizes everything into concentration first, then returns a draw volume and matching syringe-unit result.
- 10 mg equals 10,000 mcg
- 10,000 mcg / 2 mL = 5,000 mcg per mL
- 2,500 mcg / 5,000 mcg per mL = 0.5 mL
Tirzepatide 10 mg vial with 2 mL example
A 10 mg tirzepatide vial mixed with 2 mL gives 5 mg/mL, or 5,000 mcg/mL.
A 2.5 mg target dose is 2,500 mcg. At 5 mg/mL, that is 0.5 mL, which equals 50 units on a U-100 syringe.
- 10 mg / 2 mL = 5 mg/mL
- 2.5 mg = 2,500 mcg
- 2,500 mcg / 5,000 mcg per mL = 0.5 mL = 50 U-100 units
Tirzepatide 15 mg vial with 3 mL example
A 15 mg tirzepatide vial mixed with 3 mL also gives 5 mg/mL, or 5,000 mcg/mL.
Because the concentration is the same as the 10 mg with 2 mL example, a 2.5 mg dose is still 0.5 mL, or 50 U-100 units.
- 15 mg / 3 mL = 5 mg/mL
- 2.5 mg / 5 mg per mL = 0.5 mL
- 0.5 mL x 100 = 50 U-100 units
How much BAC water for tirzepatide?
Bacteriostatic water volume sets your concentration, so it directly changes the syringe units you draw. There is no single correct amount — choose a volume that puts your target dose at an easy-to-read number of units on a U-100 syringe.
For a 10 mg vial: 1 mL gives 10 mg/mL (a 2.5 mg dose = 0.25 mL = 25 units), 2 mL gives 5 mg/mL (2.5 mg = 0.5 mL = 50 units), and 3 mL gives about 3.33 mg/mL (2.5 mg = 0.75 mL = 75 units).
- More BAC water = lower concentration = more units for the same dose
- 10 mg / 1 mL = 10 mg/mL; 10 mg / 2 mL = 5 mg/mL; 10 mg / 3 mL = 3.33 mg/mL
- Aim for a draw that lands on clear unit markings to reduce dosing error
When to re-check the math
Recalculate when you change vial size, BAC water volume, dose, syringe type, or syringe capacity. Saving the setup in PepSync helps avoid re-entering the same details each week.