Tirzepatide Reconstitution Calculator

This page converts three values you already have into the syringe number you can verify before drawing: total tirzepatide in the vial, BAC water added, and the per-injection mg amount from your prescription or protocol.

It does not choose a protocol, adjust a protocol, or tell you whether tirzepatide is appropriate. It is arithmetic for a vial you already have.

• Concentration equals vial mg divided by BAC water mL.
• Volume equals target mg divided by concentration.
• U-100 units equal volume in mL times 100.

FDA-approved Mounjaro and Zepbound products are sold as ready-to-use injections, so their labels are not reconstitution instructions. Compounded and research-market tirzepatide vials are the surfaces where reconstitution math shows up.

Public reconstitution examples commonly use 5 mg, 10 mg, 15 mg, 20 mg, and 30 mg total-vial amounts. Treat those as calculator presets, not as a claim about your pharmacy's product. Your vial label and pharmacy instructions are the source of truth.

The branded labels are still useful for context because they identify tirzepatide strength in mg and set storage expectations for commercial tirzepatide products.

Bacteriostatic Water for Injection, USP is sterile water with benzyl alcohol added as a preservative and is supplied for repeated withdrawals when used to dilute or dissolve drugs for injection. BAC water changes concentration; it does not change the total tirzepatide in the vial.

A 10 mg vial mixed with 1 mL becomes 10 mg/mL. The same 10 mg vial mixed with 2 mL becomes 5 mg/mL. The same vial mixed with 3 mL becomes 3.333 mg/mL.

More water gives larger, easier-to-see draw volumes. Less water gives smaller draw volumes, which can matter if a higher mg amount would exceed a 1 mL syringe.

The FDA labels for Mounjaro and Zepbound instruct storage in a refrigerator at 36 F to 46 F (2 C to 8 C), protected from light in the original carton. Single-dose pens and single-dose vials may be kept unrefrigerated up to 86 F (30 C) for a total of 21 days.

Those branded storage rules are for Lilly's finished products, not a blanket stability guarantee for every compounded vial. For a compounded or reconstituted vial, follow the pharmacy's storage instructions and BUD first.

Do not freeze tirzepatide products. If a label or pharmacy handout says to discard after freezing, treat that as controlling.

CDC injection-safety guidance says an opened multi-dose vial should be dated and discarded within 28 days unless the manufacturer specifies a different opened-vial date. This is the common BUD norm people mean when they refer to the 28-day rule.

A compounded tirzepatide vial can have more than one clock: the reconstitution date, the first-puncture date, the BAC-water bottle's first-puncture date, and the pharmacy-specified BUD. Use the earliest applicable date.

If your pharmacy provides a shorter or longer BUD for its specific formulation, use that written instruction rather than a generic web rule.

U-100 means 100 units per mL. On a U-100 syringe, 10 units is 0.10 mL, 25 units is 0.25 mL, 50 units is 0.50 mL, and 100 units is 1.00 mL.

Most tirzepatide reconstitution examples assume U-100 insulin syringes. U-40 syringes use a different scale, so the same liquid volume reads as a different unit number.

If a calculated draw is near 100 units, it may fill a 1 mL U-100 syringe. Verify the physical syringe capacity before drawing.

Mounjaro and Zepbound pens do not need this calculator because the device already contains a measured amount. Some Zepbound vial formats are also ready-to-use commercial products rather than lyophilized powder for home reconstitution.

This page is for vial-and-water arithmetic. If your product is a ready-to-use pen, single-dose vial, multi-dose vial, or KwikPen, use the manufacturer's instructions instead of applying reconstitution math to it.