How to Reconstitute Semaglutide: Step-by-Step Mixing Guide for Every Vial Size

Semaglutide is a research peptide that ships as a freeze-dried (lyophilized) powder. Reconstituting means adding bacteriostatic water (BAC water) to dissolve that powder into a measurable liquid. The powder itself has no volume you can draw, so the water you add sets every unit you measure later.

This is a general reference for handling 5mg and 10mg vials. It is educational only and not medical advice. Peptides are research compounds not approved for human consumption, and any dosing decision belongs to a licensed clinician. The math below shows how vial size and water volume change concentration, then sends you to a calculator for exact numbers.

What reconstitution actually changes

The milligrams of powder in the vial never change. Only the concentration changes, based on how much water you add. Concentration is what your syringe reads in units.

• Total peptide is fixed by the label: 5mg or 10mg.
• BAC water volume is your choice: more water means a more dilute, lower-concentration mix.
• Concentration = total mg divided by water mL. This drives units per dose.
• Insulin syringe scale: a U-100 syringe has 100 units per 1mL, so units map directly to the mL you draw.

Supplies for neutral handling

• The sealed semaglutide vial (5mg or 10mg)
• Bacteriostatic water (see bacteriostatic water vs sterile water)
• An alcohol prep pad for both rubber stoppers
• A U-100 insulin syringe for transferring water
• A clean, flat surface and a timer

Step-by-step: mixing a 5mg vial

A common reference is adding 2mL of BAC water to a 5mg vial. That gives 5mg / 2mL = 2.5mg per mL, or 2,500mcg per mL. On a U-100 syringe, 2mL spans the full 100-unit scale across two draws, so 1 unit equals 25mcg.

1. Wipe both rubber stoppers with an alcohol pad and let them dry.
2. Draw 2mL of BAC water into the syringe (or split into two 1mL draws).
3. Angle the needle so water runs down the inner glass wall, not directly onto the powder.
4. Let the vial sit until the powder dissolves on its own. Do not shake. Gently swirl if needed.
5. Once the liquid is clear, label the vial with the date and concentration.

If you instead add 1mL to the same 5mg vial, concentration doubles to 5mg/mL (5,000mcg/mL), so each unit holds 50mcg. Same powder, half the water, twice the strength per unit.

Step-by-step: mixing a 10mg vial

For a 10mg vial, adding 2mL of BAC water gives 10mg / 2mL = 5mg per mL, or 5,000mcg per mL. That is the same per-unit value as a 5mg vial reconstituted with 1mL: 1 unit = 50mcg. The handling steps are identical to the 5mg vial.

• 10mg + 1mL water = 10mg/mL (10,000mcg/mL), 1 unit = 100mcg
• 10mg + 2mL water = 5mg/mL (5,000mcg/mL), 1 unit = 50mcg
• 10mg + 4mL water = 2.5mg/mL (2,500mcg/mL), 1 unit = 25mcg

Getting exact units per dose

Once concentration is set, units per dose is just target dose divided by concentration. Rather than redo the arithmetic each time, run the numbers through the semaglutide calculator. Enter vial strength, BAC water volume, and target dose, and it returns the exact units to draw on a U-100 syringe.

For a full worked walkthrough see semaglutide units per dose, and to plan water volume before you mix, the reconstitution calculator covers any vial size. For storage of the finished mix, review how to store peptides.

All values here are reference math, not dosing instructions. Any decision about use belongs to a qualified clinician. See the disclaimer for full terms.