Dose ↔ units
How long will my vial last?
Uses the vial and dose from the calculator above.
Real vials can hold slightly more or less than the label says, and a little is lost in the needle.
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Questions
Semaglutide is the active ingredient in Ozempic® and Wegovy®. Tirzepatide is the active ingredient in Mounjaro® and Zepbound®. Compounded versions usually come in vials with the strength printed on the label, and each dose is drawn with an insulin syringe.
How do I convert mg to units?
Divide your dose in mg by your vial's strength in mg/mL to get mL, then multiply by 100 to get units on a U-100 insulin syringe. Example numbers only: a 2.5 mg dose from a 10 mg/mL vial is 2.5 ÷ 10 = 0.25 mL, which is 25 units. Your prescriber or pharmacist sets your actual dose.
What's the difference between U-100 and U-40 syringes?
A U-100 syringe has 100 unit marks per mL; a U-40 syringe has 40 per mL. The same mark means a different amount of liquid, so a units number is only correct for the syringe type it was calculated for. This calculator uses U-100 syringes.
How do I work out the strength of a powder vial after adding water?
Divide the mg of powder in the vial by the mL of water you added. Example numbers only: 10 mg mixed with 2 mL of water gives 10 ÷ 2 = 5 mg/mL. Follow your pharmacy's mixing instructions.
How long will my vial last?
Multiply the vial size in mL by its strength in mg/mL to get the total mg, then divide by your dose to get the number of full doses. Example numbers only: a 1 mL vial at 10 mg/mL holds 10 mg, which is 4 doses of 2.5 mg. Real vials can hold slightly more or less than the label says.
Is this medical advice?
No. Vialwise is a math tool, not medical advice. Always confirm your dose and syringe amount with your prescriber or pharmacist, and check your vial label.