How much bacteriostatic water do I add to a tirzepatide vial?

A common research setup uses 1 mL of bacteriostatic water for every 10 mg of tirzepatide, which holds the concentration at 10 mg/mL across vial sizes. A 5 mg vial gets 0.5 mL, a 10 mg vial gets 1 mL, and a 30 mg vial gets 3 mL. Use the calculator to confirm the units for your exact vial and dose.

What concentration should I reconstitute tirzepatide to?

10 mg/mL is a common reference concentration because it lands a 5 mg dose on an exact 50-unit mark on a U-100 insulin syringe. Scaling the water to the vial size (1 mL per 10 mg) keeps that concentration constant across the 5 mg, 10 mg, 15 mg, 30 mg, and 60 mg vial sizes.

How many units is a 5 mg tirzepatide dose?

At the standard 10 mg/mL concentration, a 5 mg dose is 50 units on a U-100 insulin syringe. This holds for any vial size, as long as the water volume was scaled to keep the concentration at 10 mg/mL.

Tirzepatide Reconstitution Calculator: Vial & Syringe Math

By PeptCalc Research — Medically reviewed by David Mansour, MD — Last reviewed July 10, 2026

Tirzepatide is supplied as lyophilized powder and must be reconstituted with a liquid before it can be measured. This reference explains how a tirzepatide reconstitution calculator turns a vial size, water volume, and target dose into the exact number of units to draw on a U-100 insulin syringe. It is written for research purposes only and is not medical advice.

What the calculator does

The peptide calculator handles the reconstitution math in two directions:

Forward mode — enter vial size, water volume, and target dose → it returns the syringe units to draw.
Reverse mode — enter vial size, target dose, and desired syringe units → it tells you how much water to add.

Both modes work from the same formula: concentration equals mass divided by volume, and dose in units equals dose in volume times 100 (on a U-100 syringe).

Common tirzepatide vial sizes

Research vials are typically supplied in:

5 mg
10 mg
15 mg
30 mg
60 mg

The calculator supports any vial size. These five are the most frequently seen for tirzepatide.

Typical research concentration

A common reconstitution setup for tirzepatide scales the water to the vial size at 1 mL per 10 mg, which holds the concentration at a constant 10 mg/mL no matter which vial you're working from:

Vial size	Water added	Concentration
5 mg	0.5 mL	10 mg/mL
10 mg	1 mL	10 mg/mL
15 mg	1.5 mL	10 mg/mL
30 mg	3 mL	10 mg/mL
60 mg	6 mL	10 mg/mL

Because the ratio is fixed, the units for a given dose don't change with vial size — only the number of full doses the vial holds changes.

Target dose	Units at 10 mg/mL
2.5 mg	25 units
5 mg	50 units
7.5 mg	75 units
10 mg	100 units

A 5 mg dose landing on an exact 50-unit mark is a large part of why 10 mg/mL is a common reference concentration — it reads cleanly on any U-100 syringe.

The math

Step 1: Calculate concentration

Concentration = vial mass ÷ water volume

5 mg vial + 0.5 mL water = 10 mg/mL
10 mg vial + 1 mL water = 10 mg/mL
30 mg vial + 3 mL water = 10 mg/mL

Step 2: Convert dose to volume

Volume (mL) = dose (mg) ÷ concentration (mg/mL)

Example: 5 mg dose at 10 mg/mL concentration = 5 ÷ 10 = 0.5 mL

Step 3: Convert volume to syringe units

On a U-100 insulin syringe, 1 mL = 100 units, so:

Units = volume (mL) × 100

Example: 0.5 mL × 100 = 50 units

The calculator performs these three steps instantly for any vial, water, and dose combination you enter.

Reconstitution process

Gather supplies — the tirzepatide vial, bacteriostatic water, U-100 insulin syringes, alcohol swabs.
Swab both vial stoppers with alcohol.
Draw the calculated water volume (e.g. 1 mL for a 10 mg vial).
Inject slowly down the inside wall of the vial, not directly onto the powder.
Swirl gently — do not shake. Let it dissolve completely.
Verify the concentration matches what you entered in the calculator.

For a detailed walkthrough, see How to Reconstitute Peptides.

Storage

Reconstituted peptide vials are generally stored refrigerated and protected from light. Unreconstituted lyophilized powder is stable at room temperature until the expiration date on the vial. Track the reconstitution date so you know how long a given vial has been mixed.

Why the ratio matters

Some peptides are reconstituted with a fixed water volume regardless of vial size, which means concentration — and therefore units per dose — shifts with vial size. Tirzepatide's common reference setup does the opposite: water scales with mass so the concentration, and the units for any given dose, stay the same across vial sizes:

5 mg dose, any vial size, at the 1 mL per 10 mg ratio:

Vial size	Water added	Concentration	Units for a 5 mg dose
5 mg	0.5 mL	10 mg/mL	50 units
15 mg	1.5 mL	10 mg/mL	50 units
30 mg	3 mL	10 mg/mL	50 units
60 mg	6 mL	10 mg/mL	50 units

If you'd rather use a different water volume — a bigger vial with less water for a more concentrated draw, for instance — the tirzepatide reconstitution calculator's reverse mode will show you the resulting units for any combination.

Common mistakes

Confusing mg and mcg. Tirzepatide vials and doses are generally described in milligrams (mg), not micrograms (mcg). Double-check your units before drawing.
Shaking the vial. Swirl gently instead — shaking can degrade the peptide.
Not scaling the water to the vial size. Using the same water volume across a 5 mg and a 60 mg vial produces very different concentrations. Recalculate for each vial size rather than reusing a number from memory.
Using a non-U-100 syringe. The calculator assumes a standard U-100 insulin syringe (100 units = 1 mL). If your syringe is marked differently, the unit conversion will not match.

Use the tirzepatide reconstitution calculator

Enter your tirzepatide vial size, bacteriostatic water volume, and target dose into the free peptide calculator to see the exact syringe units. Reverse mode also works — enter your target dose and the units you want to draw, and it tells you how much water to add.

For related math, see the retatrutide dosage calculator guide, the tesamorelin reconstitution calculator guide, or the general how to reconstitute peptides walkthrough. The calculator handles the math. This guide explains what the numbers mean and where they come from.