Tirzepatide Reconstitution Calculator: Units & Dose

Pro Tip

The concentration trap. The same dose can be a totally different number of units depending on how much BAC water you used. A 2.5mg dose is 25 units if you mixed to 10mg/mL, but 50 units if you mixed to 5mg/mL. Same powder, same dose, different unit count. That is the whole reason to run your own numbers instead of copying someone else's units.

Dose Calculation: The Math Explained

The formula is the same for any reconstituted peptide:

Concentration = Total peptide (mg) ÷ BAC water added (mL)

Units = (Target dose in mg ÷ Concentration in mg/mL) × 100

Worked example. A 30mg vial reconstituted with 2mL of BAC water has a concentration of 30 ÷ 2 = 15 mg/mL. For a 5mg weekly dose: (5 ÷ 15) × 100 = 33.3 units. Round to 33 units. That 30mg vial at 5mg per week gives you about 6 weekly doses, roughly 6 weeks per vial.

Milligrams vs Units: The Mistake That Throws People Off

This is the mix-up that trips people up more than any other: your dose and your units are not the same number.

Your dose is the amount of actual tirzepatide, measured in milligrams (say, 5mg). Units are just the marks on your insulin syringe, and all they measure is how much liquid you are drawing up. So "5mg" and "33 units" can be the exact same dose. The milligrams tell you how much drug. The units tell you how far up the syringe to pull.

The thing that connects the two is your concentration, which is set by how much BAC water you used to mix the vial. Mix it stronger and your 5mg sits at fewer units. Mix it weaker and the same 5mg sits at more units.

That is why you cannot just copy someone else's units. If they mixed their vial differently than you mixed yours, their 5mg lands at a different mark than your 5mg. Same dose, different units. Always run it against your own vial.

Common Vial Sizes and Dose Charts

10mg Vial + 2mL BAC Water (5.0 mg/mL)

Target Dose	Units to Draw	Doses Per Vial
2.5 mg	50 units	4 doses
5.0 mg	100 units	2 doses

30mg Vial + 2mL BAC Water (15.0 mg/mL)

Target Dose	Units to Draw	Doses Per Vial
2.5 mg	17 units	12 doses
5.0 mg	33 units	6 doses
7.5 mg	50 units	4 doses
10.0 mg	67 units	3 doses
12.5 mg	83 units	~2 doses
15.0 mg	100 units	2 doses

60mg Vial + 2mL BAC Water (30.0 mg/mL)

Target Dose	Units to Draw	Doses Per Vial
2.5 mg	8 units	24 doses
5.0 mg	17 units	12 doses
7.5 mg	25 units	8 doses
10.0 mg	33 units	6 doses
12.5 mg	42 units	~4 doses
15.0 mg	50 units	4 doses

Titration Schedule

The labeled Mounjaro and Zepbound schedule uses six dose tiers, with at least 4 weeks between increases: 2.5 → 5 → 7.5 → 10 → 12.5 → 15mg per week. Not everyone needs to reach 15mg. Many people stabilize at 5, 7.5, or 10mg once appetite and weight loss are where they want them.

Storage After Reconstitution

Reconstituted tirzepatide is good for about 28 days when refrigerated between 36 and 46°F (2 to 8°C). Keep the vial upright, away from direct light, and never freeze it. If the solution develops cloudiness, visible particles, or any discoloration, discard it. Large vials (30mg, 60mg) at low doses can outlast the 28-day window mathematically, so match your vial size to the dose you are actually running.

Mixing Steps

Swab the tops of both the tirzepatide vial and the BAC water vial with alcohol. Let them dry, about 15 to 30 seconds.
Draw your chosen volume of BAC water (typically 1 to 3mL) into an insulin syringe.
Insert the needle into the tirzepatide vial at an angle and let the water run slowly down the inside glass wall. Do not aim the stream directly at the powder.
Gently swirl or roll the vial between your palms until the powder fully dissolves. Do not shake. This usually takes 2 to 5 minutes.
Check the solution. It should be completely clear with no particles or cloudiness before you draw your first dose.

Compounded vs Brand (Mounjaro / Zepbound)

Both contain the same active ingredient, tirzepatide, a dual GIP/GLP-1 receptor agonist. Brand-name Mounjaro and Zepbound ship in pre-filled auto-injector pens at fixed doses (2.5, 5, 7.5, 10, 12.5, 15mg). Compounded tirzepatide ships as a lyophilized powder in vials, commonly 5, 10, 15, 20, 30, or 60mg, which you reconstitute with BAC water and dose with an insulin syringe. The math on this page works for any reconstituted tirzepatide vial.

Frequently Asked Questions

How much BAC water do I mix with a 20mg tirzepatide vial?

2mL of bacteriostatic water is the standard for a 20mg vial. That gives a concentration of 10 mg/mL. At that concentration, a 2.5mg dose is 25 units on a U-100 insulin syringe, 5mg is 50 units, 7.5mg is 75 units, and 10mg is 100 units (the full barrel). If you want larger doses to land lower on the syringe, use 3mL of BAC water instead.

How much BAC water should I add to my tirzepatide vial?

1 to 2mL is standard for most vial sizes. For smaller vials (5mg, 10mg), 1mL keeps things simple. For larger vials (30mg, 60mg), 2mL is recommended. It keeps the concentration manageable and the injection volumes reasonable across all dose tiers.

How much BAC water for a 5mg tirzepatide vial?

1mL of BAC water gives a 5 mg/mL concentration: 2.5mg = 50 units, 5mg = 100 units (the full barrel). Use 2mL if you want the same doses to sit lower on the syringe.

How much BAC water for a 10mg tirzepatide vial?

2mL of BAC water is the standard, giving 5 mg/mL: 2.5mg = 50 units, 5mg = 100 units. With 1mL of water you get 10 mg/mL, where 2.5mg = 25 units and 5mg = 50 units.

How much BAC water for a 15mg tirzepatide vial?

2mL of BAC water is typical, giving 7.5 mg/mL: 2.5mg = 33 units, 5mg = 67 units, 7.5mg = 100 units.

How much BAC water for a 30mg tirzepatide vial?

2mL of BAC water gives 15 mg/mL: 2.5mg = 17 units, 5mg = 33 units, 7.5mg = 50 units, 10mg = 67 units, 12.5mg = 83 units, 15mg = 100 units.

How much BAC water for a 60mg tirzepatide vial?

2mL of BAC water gives 30 mg/mL: 2.5mg = 8 units, 5mg = 17 units, 7.5mg = 25 units, 10mg = 33 units, 12.5mg = 42 units, 15mg = 50 units. Reconstituted tirzepatide is only stable for about 28 days refrigerated, so confirm you will actually use the vial before that window closes at your current weekly dose.

How many units is 2.5mg of tirzepatide?

It depends on how you reconstituted the vial. At 5 mg/mL, 2.5mg = 50 units. At 10 mg/mL, 2.5mg = 25 units. At 15 mg/mL, 2.5mg = 17 units. At 30 mg/mL, 2.5mg = 8 units. The same dose lands at a different mark depending on your concentration, which is why you cannot copy someone else's unit count.

How many units is 5mg of tirzepatide?

At 5 mg/mL it is 100 units (the full barrel). At 10 mg/mL it is 50 units. At 15 mg/mL it is 33 units. At 30 mg/mL it is 17 units.

How many units is 7.5mg of tirzepatide?

At 7.5 mg/mL it is 100 units. At 10 mg/mL it is 75 units. At 15 mg/mL it is 50 units. At 30 mg/mL it is 25 units.

How many units is 10mg of tirzepatide?

At 10 mg/mL it is 100 units (the full barrel). At 15 mg/mL it is 67 units. At 30 mg/mL it is 33 units. If 100 units does not fit in a single U-100 syringe at your concentration, mix with more BAC water so the dose sits within the barrel.

Is this a compounded tirzepatide calculator?

Yes. The math here is for any reconstituted tirzepatide vial, which is how compounded tirzepatide is sold. The molecule is the same as the one in Mounjaro and Zepbound, but compounded vials are not FDA-approved products, so purity and exact concentration depend on the compounding pharmacy. The reconstitution math itself works the same regardless of source.

Is it safe to use a 60mg vial if I'm only dosing 2.5mg per week?

Mathematically, yes, but practically, no. A 60mg vial at 2.5mg per week would last 24 weeks, but reconstituted tirzepatide is only stable for about 28 days when refrigerated. You would waste most of the vial. Start with a 10mg or 15mg vial during early titration, and move to larger vials once you reach a higher maintenance dose where you will actually finish the vial within 28 days.

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