Peptide Vial Math

How to reconstitute Tirzepatide

Add a measured volume of bacteriostatic water to the Tirzepatide vial and swirl gently. 10 mg + 2 mL = 5 mg/mL, so 2.5 mg is 0.5 mL, or 50 units on a U-100 syringe.

Tirzepatide vials come in 5, 10, 15, 30, 60 mg, so what a unit holds depends on your vial.

By Peptide Vial Math Editorial Team Reviewed by the team on (how we review) Updated Formulas unit-tested (methodology)

Tirzepatide reconstitution steps

  1. Read the vial label and confirm the total mg. This page covers 5, 10, 15, 30, 60 mg.
  2. Choose the water volume using the matrix below and write down the resulting mg/mL and mg per unit.
  3. Warm the closed vial to room temperature; swab both stoppers with alcohol and let them dry.
  4. Add the bacteriostatic water slowly down the inside wall of the vial.
  5. Swirl gently until dissolved; don't shake. Inspect: clear, no particles.
  6. Label with total mg, mL added, mg/mL, mg per unit and the date.

The full procedure, with reasons for each step, is in the general reconstitution guide.

What concentration does each Tirzepatide vial and water volume give?

What one U-100 unit holds for each Tirzepatide vial size and water volume:

Tirzepatide: mcg per U-100 unit (mg/mL in brackets) by vial size and water added
Vial1 mL2 mL2.5 mL3 mL
5 mg 50 (5)25 (2.5)20 (2)16.67 (1.67)
10 mg 100 (10)50 (5)40 (4)33.33 (3.33)
15 mg 150 (15)75 (7.5)60 (6)50 (5)
30 mg 300 (30)150 (15)120 (12)100 (10)
60 mg 600 (60)300 (30)240 (24)200 (20)

And the concentration each combination gives:

Tirzepatide: concentration, mg/mL by vial size and water added
Vial1 mL2 mL2.5 mL3 mL
5 mg 52.521.67
10 mg 10543.33
15 mg 157.565
30 mg 30151210
60 mg 60302420

If you have a prescription product, follow its label and your prescriber; it is labeled in mg and this calculator is not a substitute. FDA has received reports of dosing errors with compounded GLP-1 vials where "units", mL and mg were confused, which is exactly the conversion this page makes explicit.

Tirzepatide reconstitution calculator

Vial mg, water mL and amount give syringe units

mg

Total printed on the vial label.

mL

Diluent volume you add (1 mL = 100 units on a U-100 syringe).

Amount unit

The mass you want in one draw. 1 mg = 1,000 mcg.

Syringe barrel
Show U-40 and U-50 syringes

Result

50units

to draw on a U-100 syringe, 100-unit barrel

Vial: 10 mg with 2 mL diluent 10 mg +2 mL
Syringe filled to 50.0 of 100 units 0 10 20 30 40 50 60 70 80 90 100 U-100, 1 mL
Volume
0.5 mL
Concentration
5 mg/mL
Per unit
50 mcg
Draws per vial
4

10 mg + 2 mL = 5 mg/mL, so 2.5 mg is 0.5 mL, or 50 units on a U-100 syringe.

Arithmetic only. Not a dosing recommendation. Check every figure against your vial label and lab protocol.

Per-amount unit charts for each vial size: Tirzepatide calculator (5 mg, 10 mg, 15 mg, 30 mg, 60 mg).

Frequently asked questions

How much bacteriostatic water do you add to a 10 mg Tirzepatide vial?

There is no single correct volume; it sets the concentration. 10 mg in 1 mL is 10 mg/mL, in 2 mL is 5 mg/mL, in 3 mL is 3.33 mg/mL. With 2 mL, each U-100 unit holds 0.05 mg.

How do I reconstitute a 60 mg Tirzepatide vial?

Same procedure, different numbers. 60 mg in 2 mL is 30 mg/mL, so each unit holds 0.3 mg, 6× more than a 10 mg vial with the same water. Units copied from a smaller vial will be wrong.

What is the Tirzepatide reconstitution formula?

mg/mL = vial mg ÷ water mL; mL = amount ÷ mg/mL; U-100 units = mL × 100. Example: 10 mg + 2 mL = 5 mg/mL, so 2.5 mg is 0.5 mL, or 50 units on a U-100 syringe.

Can I change the water volume after reconstituting Tirzepatide?

Adding more diluent later is possible arithmetically (the new concentration is the remaining mg ÷ the new total volume), but you must account for what has already been drawn. It is simpler and less error-prone to choose the volume once, before mixing, and label it.

How should the Tirzepatide vial be stored after mixing?

Reconstitution changes how a vial has to be kept: a lyophilized powder and a solution have different temperature, light and time limits, and an opened multi-dose diluent vial has its own clock (CDC guidance: discard 28 days after first puncture unless the manufacturer gives another date). The peptide storage guide covers both states, and the bacteriostatic water guide covers the diluent. Label each vial with the amount, the water added, the concentration and the date.

Sources

  1. Zepbound (tirzepatide) injection: full prescribing information (revised 08/2026) — Eli Lilly and Company (FDA-approved label), 2026
  2. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss — U.S. Food and Drug Administration
  3. FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products — U.S. Food and Drug Administration, 2024
  4. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1) — N Engl J Med, 2022, PMID 35658024
  5. Handling and Storage Guidelines for Peptides — Bachem Knowledge Center
  6. Bacteriostatic Water for Injection, USP (Hospira) — prescribing label — DailyMed, U.S. National Library of Medicine

Links checked 2026-10-19.