Tirzepatide reconstitution calculator
For compounded vials dispensed on prescription by a US 503A pharmacy. Enter the strength on the label, the diluent volume your pharmacy specified and the amount it stated, and this returns the volume and the units on a U-100 syringe.
Calculator
Compounded vials only. Compounded medicines are not FDA-evaluated for safety, efficacy or quality, and a branded pen is a metered device this arithmetic does not describe.
Draw to
16.7units
on a U-100 insulin syringe (0.167 ml)
- Concentration
- 15 mg/ml
- 15000 mcg/ml
- Volume to draw
- 0.167 ml
- Doses per vial
- 12
- Syringe capacity
- 100 units
How this is calculated
concentration (mg/ml) = vial mg / water ml = 30 / 2 = 15 concentration (mcg/ml) = concentration mg/ml x 1000 = 15000 volume to draw (ml) = dose mcg / concentration mcg = 2500 / 15000 = 0.167 insulin units = volume ml x 100 = 0.167 x 100 = 16.7 doses per vial = floor(water ml / volume ml) = floor(2 / 0.167) = 12 100 units = 1 ml on every U-100 insulin syringe. Barrel size changes how much it holds, never what a unit means.
What a compounded vial is
In the United States, tirzepatide is also supplied as a compounded preparation: a 503A pharmacy prepares it against an individual prescription, and it arrives as a vial of powder or solution with the pharmacy's own preparation instructions. That is a different product and a different regulatory category from a manufactured, FDA-approved pen, which is a metered device and is not reconstituted at all. This calculator describes vials only.
Compounded medicines are not evaluated by the FDA for safety, efficacy or quality. The strength on the label, the diluent, the volume to add and the amount to draw all come from the pharmacy that dispensed it, and they vary between pharmacies for the same molecule. Prepare exactly as your pharmacy instructs; these figures are arithmetic, not a prescribing instruction.
Strengths and diluent volumes
Compounded vials are commonly dispensed at 10mg, 20mg, 30mg and 60mg, and the diluent volume is specified by the pharmacy rather than chosen by the patient. A 30mg vial in 2ml is 15 mg/ml; the same vial in 3ml is 10 mg/ml, and every unit figure downstream moves with it.
Because the concentration is a pharmacy determination rather than a convention, two vials with identical labels from different pharmacies can produce different readings on the same syringe. Enter the figures from the label and the instructions you were given, not a figure from elsewhere.
Storage and stability, in general terms
Compounded vials are dispensed with a beyond-use date, which is the pharmacy's own determination for that preparation and is typically much shorter than the shelf life of a manufactured product. It appears on the label, and it is the figure that applies.
Refrigeration, protection from light and avoidance of freezing are the general expectations for this class of preparation, and a compounded vial is not returned to room temperature for storage once it has been chilled. None of this overrides what the dispensing pharmacy states. Prepare exactly as your pharmacy instructs; these figures are arithmetic, not a prescribing instruction.
Frequently asked questions
How do I work out units from a compounded vial?
Divide the strength on the label by the diluent volume to get the concentration, divide the amount by that concentration to get millilitres, then multiply by 100. A 30mg vial in 2ml is 15000 mcg/ml, so 2500mcg is 0.167ml, which is about 16.7 units on a U-100 syringe. Prepare exactly as your pharmacy instructs; these figures are arithmetic, not a prescribing instruction.
Why do two pharmacies give different numbers for the same strength?
Because the diluent volume is the pharmacy's choice, and concentration follows from it. The same 30mg vial reconstituted in 1ml, 2ml or 3ml produces three different unit figures for the identical amount. This is why the label in front of you, rather than a figure from elsewhere, is the one to enter.
Is a compounded vial the same as a branded pen?
No. A pen is a manufactured, FDA-approved, metered device: nothing is reconstituted and nothing is drawn into a syringe. A compounded vial is prepared by a pharmacy against a prescription and is not FDA-evaluated for safety, efficacy or quality. The arithmetic here describes vials only.
What if my figure does not fit the syringe?
A 0.5ml insulin syringe holds 50 units and a 1ml holds 100. If the figure exceeds the barrel you have, that is a question for the dispensing pharmacy rather than something to resolve by adding diluent — the concentration was their determination, and changing it changes the preparation.
Does this page tell me how much to use?
No. It converts a quantity your prescription already specifies into a volume and a unit reading on a syringe. It recommends no amount, no frequency and no duration, and it names no supplier.
Before you use this
This tool performs arithmetic only. It does not recommend a dose, a frequency, a duration or a supplier. Many peptides discussed online are not approved by the FDA for the uses people describe. Compounded medicines are supplied on prescription and should be prepared exactly as your pharmacy instructs. Talk to a prescriber or pharmacist before preparing or administering anything.