Semaglutide reconstitution: how to mix and measure a vial

Semaglutide is a prescription GLP-1 medicine, approved as Ozempic for type 2 diabetes and as Wegovy for weight management. Pens from a pharmacy come ready to use and need no mixing.

This guide is for vials of dry powder. Some compounded vials come already mixed, with the strength printed on the label (for example 2.5 mg/mL); those don’t need water added.

A common choice is 2 mL of bacteriostatic water in a 5 mg vial. That makes 2.5 mg per mL, and at that strength 0.5 mg is 20 units on a U-100 insulin syringe.

The amount of water is up to you. More water makes each dose a bigger number of units, which is easier to measure; it doesn’t change how much semaglutide is in the vial. Whatever you add, work the dose out with your own numbers in the calculator.

The approved Wegovy schedule starts at 0.25 mg once a week for 4 weeks, then steps up every 4 weeks: 0.5 mg, 1 mg and 1.7 mg, to a 2.4 mg maintenance dose.

Going up faster makes nausea and vomiting much more likely. Your prescriber may use a different schedule, or keep you on a lower dose.

Unmixed powder: freezer at −20°C, or as the label says. Once mixed: fridge at 2–8°C, and use within 28 days. Don’t freeze it once it’s mixed.