How Semaglutide Is Reconstituted
Research-grade semaglutide ships as a lyophilized powder in vials ranging from 3mg to 30mg. Trial protocols and community sources describe reconstitution with bacteriostatic water before use. The process is identical to other peptides, with the dose-escalation schedule making dilution choice particularly important.
Vial size drives that choice more than anything else. The same 2mL of water gives 2,500mcg/mL in a 5mg vial and 15,000mcg/mL in a 30mg vial, so a unit count that is correct on one size is off by sixfold on the other. This guide reports the documented mixing process, a reconstitution chart for each vial size, and storage.
Research-context information only. Semaglutide is the active ingredient in FDA-approved products for diabetes and chronic weight management; research-peptide and compounded forms are not FDA-approved and are sold for research purposes only. Protocols, doses, and reactions reported below come from published clinical trials and self-reported community sources. This article reports what has been documented, not what should be done. Possession or use of investigational drugs outside an authorized clinical trial may be illegal in your jurisdiction. Consult a licensed physician for personal medical decisions.
New to bacteriostatic water? Start with what it is, how much to use per vial, and how long it lasts — or see the full Bacteriostatic Water Guide.
Materials Documented in Reconstitution Protocols
- Semaglutide lyophilized vial (sold in 3mg through 30mg sizes)
- Bacteriostatic water (BAC water) — not sterile water, not saline
- Insulin syringes — 1mL (100 unit), 29-31 gauge
- Alcohol swabs — for cleaning vial tops
- A clean, flat workspace
Why bacteriostatic water? It contains 0.9% benzyl alcohol that suppresses bacterial growth. Sterile water has no preservative, so vials reconstituted with it are typically discarded within 24 hours. Because semaglutide is dosed once weekly and a single vial can span weeks, BAC water is the documented standard — published stability data show up to 28 days refrigerated.
Documented Reconstitution Steps
Step 1: Surface Preparation
Standard reconstitution practice is to wipe the tops of both vials (semaglutide and BAC water) with alcohol swabs and allow 10 seconds to air dry. This step is consistently cited as the contamination-prevention checkpoint.
Step 2: Drawing Bacteriostatic Water
A fresh insulin syringe is used to draw the BAC water volume. The volume drawn determines the final concentration (see dilution charts below).
The most-cited dilution for 5mg vials is 2mL of BAC water. It produces clean, measurable numbers across the documented escalation from 0.25mg through 2.4mg — all within the range of a single insulin syringe.
Step 3: Adding Water to the Peptide Vial
Trial protocols describe inserting the needle into the semaglutide vial at an angle, aiming at the glass wall — not directly at the powder. The water trickles down the side of the vial.
Squirting water directly onto the powder is discouraged in standard reconstitution practice. Peptides are fragile proteins; aggressive mixing can damage molecular structure and reduce potency.
Step 4: Dissolution
Standard reconstitution practice is to swirl the vial gently with a slow rotating motion. Trial protocols specify gentle swirling rather than shaking. Properly manufactured semaglutide is documented to dissolve within 1-2 minutes into a clear, colorless solution.
Particles remaining after 5 minutes of gentle swirling are commonly cited as a sign of degraded peptide.
Step 5: Storage
Reconstituted research peptides are typically refrigerated immediately at 36-46F (2-8C) in published stability studies. Reconstituted semaglutide stability with bacteriostatic water is documented at up to 28 days.
Semaglutide Reconstitution Chart: BAC Water by Vial Size
One chart per vial size. The highlighted row is the ratio community sources most often describe for that size, chosen so both ends of the escalation range — 0.25mg at the start and 2.4mg at maintenance — stay readable on a U-100 insulin syringe.
Why the highlighted row changes with vial size. On small vials the limit is the top of the range: at 2mL in a 5mg vial the maximum 2.4mg dose is 96 units, just inside a 100-unit syringe. On large vials the limit inverts to the bottom of the range. A 30mg vial at 2mL reaches 15,000mcg/mL, where the 0.25mg starting dose is 1.7 units — below what an insulin syringe can measure with any confidence. That is why the larger sizes are documented with proportionally more water.
A practical consequence. Because the starting dose is what breaks first, community sources describe 20mg and 30mg vials as better suited to established maintenance dosing than to an initial titration, where a 5mg vial keeps every step measurable.
Dosage is a separate question from mixing. The semaglutide dosage and titration chart covers the weekly schedule and escalation steps.
The Math
The formula for any vial size and any amount of water:
Concentration = Peptide Amount (mcg) / Water Added (mL)
For injection volume:
Units to inject = Desired Dose (mcg) / Concentration (mcg/mL) x 100
Example: 5,000mcg vial + 2mL water = 2,500mcg/mL. For a 0.5mg (500mcg) dose: 500 / 2,500 x 100 = 20 units.
For the maximum dose: 2,400mcg / 2,500mcg/mL x 100 = 96 units — within a 1mL syringe.
The Reconstitution Calculator automates the math given vial size, water amount, and desired dose.
