A tirzepatide vial arrives as a powder with no concentration until you make one. How much bacteriostatic water you add decides the concentration, and the concentration decides every syringe reading afterwards. This works the whole chain using the numbers you enter.
Reconstitution calculator
Enter the vial as labelled and the bacteriostatic water you actually added. Numbers, dates and choices you enter in this tool are not saved or sent. Page analytics, described on our Privacy page, record page views and clicks but not what you type or select.
Enter the dose exactly as your prescriber wrote it. The calculator does not suggest or pre-fill dose steps.
How to Use This Calculator
Two numbers off the vial, one from your protocol, one from the syringe.
Enter the vial strengthThe milligram figure printed on the vial before you add anything: commonly 10 mg, 15 mg or 30 mg.
Enter the bacteriostatic water you addedIn mL. This is the number people most often fail to recall three weeks later, so write it down or record it against the vial.
Enter your doseThe amount your prescriber gave you, in mg.
Match your syringeCheck the barrel. A U-100 and a U-40 syringe read the same volume as very different numbers.
How the Math Works
Four steps, all plain arithmetic.
Concentration. Vial strength divided by the volume of bacteriostatic water you added, in mg/mL. Every number below depends on this one, and it changes if you reconstitute the next vial differently. Standard reconstitution arithmetic.
Draw volume. Your dose divided by the concentration, in mL.
Syringe reading. Draw volume multiplied by the syringe's units-per-mL rating. A U-100 and a U-40 syringe give different readings for an identical volume. Check what is printed on the barrel. ISO 7864 syringe graduation standards.
Doses per vial. Vial strength divided by your dose. A larger dose means fewer doses per vial, which is also why cost per dose rises. See the Cost Planner.
Why tirzepatide is unforgiving of a misread
Two things specific to this compound rather than generic advice.
Small doses are very small volumes. A small dose drawn from a concentrated vial can be a fraction of a millilitre, and at that scale a misread of a couple of units is a proportionally large error. If your draw is coming out under about 5 units, more diluent gives a larger and easier-to-read volume.
Doses per vial change at every step. The same vial yields fewer doses as the dose gets larger, so a supply plan made at one dose stops being true when the dose changes. The Vial Longevity Calculator recalculates it.
Arithmetic only, not medical advice. This calculator divides numbers you enter. It does not recommend a dose, a diluent volume, a syringe, or a product, and it cannot verify what is actually in your vial. Your prescriber sets your actual dose and schedule. Peptide Plug does not sell, supply or source any compound.
Frequently Asked Questions
How much bacteriostatic water should I add to a tirzepatide vial?
That is a protocol decision for you and your prescriber or pharmacist, not something this calculator determines. It works with whatever volume you actually added. What matters is that you record the volume, because every syringe reading depends on it.
Why is my syringe reading different from someone else's at the same dose?
Because concentration and syringe rating both differ. The same milligram dose drawn from a differently reconstituted vial, or measured on a differently rated syringe, produces a different unit reading. Neither of you is necessarily wrong.
Does this calculator include the labelled dose steps?
No. Enter each dose your prescriber gives you. For the approved dosing schedule, see the official prescribing information for your product.
Does more bacteriostatic water weaken the medication?
It lowers the concentration, not the total amount in the vial. You draw a larger volume for the same dose. The practical trade-off is that a very dilute solution needs a larger draw, and a very concentrated one needs a draw small enough to be hard to measure.
How many doses will my vial give me?
Vial strength divided by your dose, shown above. Expect slightly fewer in practice: residual volume, drawing waste and the discard window all cut into the theoretical count.
How long does a reconstituted tirzepatide vial last?
That depends on the product and storage conditions, and this page does not supply a figure. The Medication Storage Calculator works through discard windows from published storage guidance, and a pharmacist can confirm for your product.
Does Peptide Plug sell tirzepatide?
No. Peptide Plug is a tracking and calculation tool. We do not sell, supply, source or link to vendors for any compound.
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Tracking tool, not medical advice. Peptide Plug is an organization and calculation tool for adults 18 and older. It does not provide medical advice, diagnosis or treatment, and it does not recommend, suggest or verify any substance, amount, schedule or route. Calculators only perform arithmetic on the numbers you enter; double-check every result. Many compounds referenced on this site are not FDA-approved for human use, and products sold outside an approved supply chain are not verified for identity, purity or concentration. Peptide Plug does not sell, supply, source or link to sellers of any compound. Confirm every decision with a licensed clinician or pharmacist. In an emergency, call 911.
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