Vial Guide

Tirzepatide 100 mg vial

How much bacteriostatic water to add to a 100 mg vial of Tirzepatide, the syringe units for each common dose, and how many doses the vial holds.

Water
4 mL
Strength
25 mg/mL
Common dose
2.5 mg
Draw
10 units0.10 mL
Doses per vial
40

The short answer

Mixed with 4 mL of bacteriostatic water, a 100 mg vial of Tirzepatide holds 25 mg/mL. A 2.5 mg dose is then 10 units (0.10 mL) on a U-100 insulin syringe, and the vial holds about 40 doses of that size. Taken 1× per week, it lasts about 40 weeks.

Approved drug. FDA-approved as Mounjaro (type 2 diabetes in adults and children 10 and older, including lowering heart attack and stroke risk in high-risk adults) and Zepbound (weight management and obstructive sleep apnea).
Tirzepatide page

How much water

The water only sets the strength; the dose and the number of doses in the vial stay the same. Draws are on a U-100 insulin syringe, where 1 unit is 0.01 mL.

Water addedStrengthPer syringe unitDraw for 2.5 mg
2 mL50 mg/mL500 mcg5 units (0.05 mL)
3 mL33.33 mg/mL333 mcg7.5 units (0.075 mL)
4 mL25 mg/mL250 mcg10 units (0.10 mL)

Dose chart

Syringe units for each common dose at each water volume. Select a cell to open it in the calculator.

DoseWater added
2 mL3 mL4 mL
2.5 mg
5 mg
7.5 mg
10 mg
12.5 mg
15 mg

Draws over 100 units show in mL. Faded values are under 2 units, which is hard to measure. Check that your vial holds the larger volumes.

Where the doses come from

  • Label 2.5 mg once weekly for 4 weeks, then 5 mg. Further 2.5 mg steps come after at least 4 weeks on the current dose. Zepbound maintenance is 5, 10 or 15 mg for weight and 10 or 15 mg for sleep apnea; Mounjaro steps up only if blood sugar needs it. Maximum 15 mg (10 mg for children on Mounjaro).

Doses are what labels, trials or community reports reference, not recommendations. Tirzepatide’s page has the cycle, side effects, cautions and sources.

Mixing and storage

  1. PrepareLet a refrigerated vial come to room temperature, and wipe both stoppers with an alcohol swab.
  2. Add 4 mLDraw 4 mL of bacteriostatic water and let it run slowly down the inside wall of the vial.
  3. Swirl, don’t shakeSwirl gently until the powder dissolves and the liquid is clear.
  4. Label itWrite the date and the strength, 25 mg/mL, on the vial.

Storage: Mixed vials: 2–8 °C, protected from light. Don’t freeze.

The reconstitution guide covers each step, and the units page explains syringe markings.

Questions

How much water do I add to a 100 mg vial of tirzepatide?

There’s no single right amount: the water only sets the strength. With 4 mL of bacteriostatic water, a 100 mg vial holds 25 mg/mL. With 2 mL it’s 50 mg/mL; with 3 mL it’s 33.33 mg/mL. Less liquid makes each dose a smaller draw; more makes small doses easier to measure.

How many units is 2.5 mg of tirzepatide?

With 4 mL in a 100 mg vial, 2.5 mg is 10 units (0.10 mL) on a U-100 insulin syringe. With 2 mL, 5 units (0.05 mL); with 3 mL, 7.5 units (0.075 mL).

How many doses are in a 100 mg vial of tirzepatide?

About 40 doses of 2.5 mg, or 8 of 12.5 mg or 6 of 15 mg. Taken 1× per week at 2.5 mg, it lasts about 40 weeks.

How long does a mixed vial of tirzepatide keep?

Mixed vials: 2–8 °C, protected from light. Don’t freeze.

Other vial sizes

Sources

  • Zepbound prescribing information, rev. 08/2026 (Eli Lilly)
  • Mounjaro prescribing information, rev. 08/2026 (Eli Lilly)

The math on this page uses the doses and storage on Tirzepatide’s page.

By Vial Guide editorsLast reviewed

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