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

Use the volume in your product's instructions or from your prescriber or pharmacist. The water doesn't change how much tirzepatide is in the vial, only the concentration: a 10 mg vial with 2 mL is 5 mg/mL, and adding more water makes each unit on the syringe hold less.

How do I convert tirzepatide from mg to syringe units?

Divide the amount in mg by the concentration in mg/mL to get mL, then multiply by 100 for a U-100 insulin syringe (50 for U-50, 40 for U-40). The calculator on this page does it when you enter the amount from your prescriber or label.

Does this calculator give a tirzepatide dose?

No. The calculator's amount field starts empty and Caliper never suggests an amount. For reference, this page quotes the dosing section of the FDA label for Zepbound and Mounjaro, which applies only to that branded product. Your dose comes from your prescriber.

How should I store tirzepatide after mixing?

Follow the storage section of your product's label or the pharmacy's instructions. The notes on this page summarize what the FDA label says for the branded product. For any mixed vial, write the mixing date on it and respect the use-by date.

Do Zepbound vials need reconstitution?

No. Zepbound single-dose and multi-dose vials contain a solution, and the label prints the strength. The label tells prescribers to have patients use a syringe appropriate for the dose, such as a 1 mL syringe, and a new syringe and needle for each injection.

Tirzepatide reconstitution calculator

Concentration and syringe-unit math for tirzepatide vials (10, 15, 20 and 30 mg), with the calculator set up for a 10 mg vial and 2 mL of diluent. Change both to match your own vial.

FDA-approved product existsGLP-1 and incretin compounds

Tirzepatide is a GIP and GLP-1 receptor agonist. The FDA-approved brands are Zepbound (weight reduction and obstructive sleep apnea) and Mounjaro (type 2 diabetes). Both come as ready-to-use solutions in pens, KwikPens and vials.

FDA-approved product: Zepbound and Mounjaro. The official label dosing for the branded product is quoted further down this page for reference. It applies only to that product, and it is never filled into the calculator. Products sold for “research use only” are not the approved drug.

Reconstitution calculator

Enter the numbers from your own vial, and pick the syringe in your hand. Check the U- number and size printed on the syringe box.

Concentration

5 mg/mL

5,000 mcg/mL

Draw volume

—

Syringe units

—

U-100 1 mL, holds 100

Draws in the vial

—

1Concentration: 10 mg ÷ 2 mL = 5 mg/mL
2Draw volume: amount in mg ÷ 5 mg/mL = draw mL
3Syringe units: draw mL × 100 units per mL (U-100) = units

Math only, not dosing advice. Follow your prescriber or label. Real vials give slightly less than the full-draw count: a little liquid stays in the vial and needle. Your last setup is saved in this browser only; Clear removes it.

Save your vial in Caliper and it remembers the concentration and use-by date you entered, alongside your dose log. The calculator above is a browser tool and is not part of the app.

Save my vial in Caliper

The calculator starts with a 10 mg vial and 2 mL of diluent as an example setup, not a recommendation. Enter the vial size on your label and the volume you actually added. The amount field starts empty: Caliper never suggests an amount.

Tirzepatide concentration by vial size

Vial mg ÷ mL of diluent = mg per mL. Plain arithmetic for tirzepatide label sizes; the volumes are examples, not recommendations.

Tirzepatide: mg/mL by vial size and diluent volume
Vial	1 mL	2 mL	3 mL
10 mg	10 mg/mL	5 mg/mL	3.333 mg/mL
15 mg	15 mg/mL	7.5 mg/mL	5 mg/mL
20 mg	20 mg/mL	10 mg/mL	6.667 mg/mL
30 mg	30 mg/mL	15 mg/mL	10 mg/mL

Syringe units to mg at 5 mg/mL

What a given number of U-100 units holds when a 10 mg vial has 2 mL added. This is a unit conversion, like a map scale, not a dose. A different vial size or volume changes every row, so use the calculator for your own numbers.

10 mg vial + 2 mL (5 mg/mL): conversion only
U-100 units	mL	mg	mcg
5 units	0.05	0.25	250
10 units	0.1	0.5	500
20 units	0.2	1	1,000
25 units	0.25	1.25	1,250
50 units	0.5	2.5	2,500

Mixing and storing tirzepatide

Zepbound and Mounjaro vials are already in solution: nothing is added. Their labels print the concentration, for example the multi-dose vials state the total strength per 2.4 mL and the strength per mL, so you can enter the strength per mL straight into the units-to-mg converter.

For a powder vial, the calculator divides the vial's mg by the diluent you add. A 10 mg vial with 2 mL is 5 mg/mL; a 30 mg vial with the same 2 mL is 15 mg/mL, so each unit holds three times as much. Recalculate whenever the vial size or volume changes.

Zepbound single-dose pens and vials are labeled for refrigeration at 2°C to 8°C (36°F to 46°F) and can be kept unrefrigerated up to 30°C (86°F) for a total of 21 days. The label says to throw away an opened multi-dose vial or KwikPen after a total of 30 days at room temperature, 30 days after first use, or after 4 weekly doses, even if medicine is left.

Status: FDA-approved as Zepbound and Mounjaro. Powder vials labeled tirzepatide are compounded or research products, not the FDA-approved drug.

More detail: how to reconstitute peptides and how to store peptides and GLP-1s. To convert units you've already drawn, use the units-to-mg converter.

Official FDA label dosing for Zepbound and Mounjaro

Follow your prescriber's instructions. This is not medical advice. The text below is quoted exactly from the current FDA prescribing information (section cross-references removed). It is the official label schedule for the branded product named and does not apply to compounded or research products. Labels change; the linked label is the authority.

ZEPBOUND: label schedule

Indication (from the label): “ZEPBOUND® is indicated in combination with a reduced-calorie diet and increased physical activity: to reduce excess body weight and maintain weight reduction long term in adults with obesity or adults with overweight in the presence of at least one weight-related comorbid condition. … to treat moderate to severe obstructive sleep apnea (OSA) in adults with obesity.”

“The recommended starting dosage is 2.5 mg injected subcutaneously once weekly for 4 weeks. Increase the dosage in 2.5 mg increments after at least 4 weeks until recommended maintenance dosage is achieved.”
“Consider treatment response and tolerability when selecting the maintenance dosage.”
“Weight Reduction and Long-Term Maintenance: 5 mg, 10 mg, or 15 mg injected subcutaneously once weekly.”
“Obstructive Sleep Apnea: 10 mg or 15 mg injected subcutaneously once weekly.”
“Maximum Recommended Dosage: 15 mg injected subcutaneously once weekly.”
“The 2.5 mg dosage is for treatment initiation and is not approved as a maintenance dosage.”

Source: ZEPBOUND (tirzepatide) prescribing information, DailyMed, label version effective August 28, 2026; checked October 17, 2026.

MOUNJARO: label schedule

Indication (from the label): “MOUNJARO® is indicated: as an adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus.”

“The recommended starting dosage is 2.5 mg injected subcutaneously once weekly.”
“If additional glycemic control is needed, increase the dosage in 2.5 mg increments after at least 4 weeks on the current dose.”
“Maximum dosage: Adults: 15 mg subcutaneously once weekly. Pediatric patients 10 years of age and older: 10 mg subcutaneously once weekly.”

Source: MOUNJARO (tirzepatide) prescribing information, DailyMed, label version effective August 27, 2026; checked October 17, 2026.

FAQ

How much bacteriostatic water do I add to a tirzepatide vial?: Use the volume in your product's instructions or from your prescriber or pharmacist. The water doesn't change how much tirzepatide is in the vial, only the concentration: a 10 mg vial with 2 mL is 5 mg/mL, and adding more water makes each unit on the syringe hold less.
How do I convert tirzepatide from mg to syringe units?: Divide the amount in mg by the concentration in mg/mL to get mL, then multiply by 100 for a U-100 insulin syringe (50 for U-50, 40 for U-40). The calculator on this page does it when you enter the amount from your prescriber or label.
Does this calculator give a tirzepatide dose?: No. The calculator's amount field starts empty and Caliper never suggests an amount. For reference, this page quotes the dosing section of the FDA label for Zepbound and Mounjaro, which applies only to that branded product. Your dose comes from your prescriber.
Is tirzepatide FDA-approved?: FDA-approved as Zepbound and Mounjaro. Powder vials labeled tirzepatide are compounded or research products, not the FDA-approved drug.
How should I store tirzepatide after mixing?: Follow the storage section of your product's label or the pharmacy's instructions. The notes on this page summarize what the FDA label says for the branded product. For any mixed vial, write the mixing date on it and respect the use-by date.
Do Zepbound vials need reconstitution?: No. Zepbound single-dose and multi-dose vials contain a solution, and the label prints the strength. The label tells prescribers to have patients use a syringe appropriate for the dose, such as a 1 mL syringe, and a new syringe and needle for each injection.

Related compounds

Calculators by vial size

The same arithmetic for any compound, with a 1, 2 and 3 mL concentration table.

Related guides

Sources

Updated October 17, 2026

For adults 18+. Educational math only, not medical advice. This page does not recommend any dose, dilution, syringe or compound, and doesn't say where to get one. Always follow your prescriber's instructions and the product label, and ask a pharmacist if a number doesn't look right.