How to convert a compounded GLP-1 dose into units
Compounded GLP-1 medications come as a powder to reconstitute or a pre-mixed vial, drawn with an insulin syringe. Manufactured pens dial their own dose — see the warning above.
- Confirm it is a compounded vial, not a pen. A pen doses itself; only a vial is drawn with a syringe.
- Reconstitute if it is a powder. Add bacteriostatic water to set the concentration — more water makes small starting doses easier to measure.
- Enter your prescribed dose to read the exact units to draw on a U-100 syringe.
- Draw, inject, and log so next week the math is already done for you.
Worked example: a 5 mg semaglutide vial at a 0.25 mg dose
A common compounded starting setup — a 5 mg vial reconstituted with 2 mL of BAC water, at a 0.25 mg weekly dose:
- Concentration — 5 mg ÷ 2 mL = 2.5 mg/mL (2500 mcg/mL).
- Volume for your dose — 0.25 mg ÷ 2.5 mg/mL = 0.1 mL.
- Units to draw — 0.1 mL × 100 units/mL = 10 units on a U-100 syringe.
- Doses per vial — 5 mg ÷ 0.25 mg = 20 doses.
Enter your own vial strength, water, and dose above — the calculator keeps compounded and pen products separate so the two never get confused.
Frequently asked questions
What is the difference between a compounded GLP-1 vial and a pen?
A manufactured pen (Ozempic, Wegovy, Mounjaro, Zepbound) is pre-filled and dials its own dose — you never calculate units. A compounded vial from a pharmacy is drawn with an insulin syringe, so you convert your prescribed dose into units. This calculator is only for the compounded vial workflow.
How much bacteriostatic water should I add to a compounded GLP-1 vial?
The water only sets the concentration, not the dose. A common choice is 2 mL for a 5 mg vial (2.5 mg/mL). More water makes each unit less concentrated, which can make small starting doses easier to measure accurately. Follow the instructions from your compounding pharmacy or provider.
Does the calculator work for both semaglutide and tirzepatide?
Yes. The math is identical for any compounded injectable — vial strength, water volume, and dose determine the units. Enter your own numbers; the tool does not assume a drug or recommend a dose.
What is a “unit” on the syringe?
Units refer to the U-100 insulin scale, where 100 units = 1 mL, so 10 units is 0.1 mL. Insulin syringes are marked in units, which is why compounded doses are converted to units rather than millilitres.
Is this GLP-1 calculator medical advice?
No. It is an educational estimation tool that does the arithmetic from the numbers you enter and shows its work. It never prescribes, diagnoses, or recommends a dose. Always follow your licensed provider’s instructions.
Related calculators
