How to Reconstitute Semaglutide: Step-by-Step Guide (2026)
Semaglutide reconstitution guide: 2mL BAC water into a 5mg vial for weekly dosing. Dose escalation charts, storage, and mistakes to avoid.
How to Reconstitute Semaglutide
Research-grade semaglutide arrives as a lyophilized powder in small vials — typically 3mg or 5mg. Before it can be used, you need to reconstitute it with bacteriostatic water. The process is identical to other peptides, but the dose escalation schedule makes your dilution choice particularly important.
This guide covers mixing, measuring doses across the full escalation range, and proper storage.
What You Need
Before you start, gather everything:
- Semaglutide lyophilized vial (typically 3mg or 5mg)
- 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 prevents bacteria from growing in your solution. Regular sterile water has no preservative, so the vial must be used within 24 hours. Since semaglutide is dosed once weekly and a single vial can last weeks, BAC water is essential — it gives you up to 28 days refrigerated.
Step-by-Step Reconstitution
Step 1: Clean Everything
Wipe the tops of both vials (semaglutide and BAC water) with alcohol swabs. Let them air dry for 10 seconds. This prevents contamination — skip it at your own risk.
Step 2: Draw Your Bacteriostatic Water
Using a fresh insulin syringe, draw your desired amount of BAC water. The amount you add determines your concentration (see the dilution charts below).
For most people, 2mL into a 5mg vial is the sweet spot. It gives clean, measurable numbers across the entire dose escalation from 0.25mg through 2.4mg — all within the range of a single insulin syringe.
Step 3: Add Water to the Peptide Vial
Insert the needle into the semaglutide vial at an angle, aiming at the glass wall — not directly at the powder. Let the water trickle down the side of the vial gently.
Do not squirt water directly onto the powder. Peptides are fragile proteins. Aggressive mixing can damage the molecular structure and reduce potency.
Step 4: Let It Dissolve
Gently swirl the vial with a slow rotating motion. Do not shake it. The powder should dissolve within 1-2 minutes into a perfectly clear, colorless solution.
If particles remain after 5 minutes of gentle swirling, the peptide may be degraded. A properly manufactured semaglutide dissolves easily.
Step 5: Store Correctly
Refrigerate immediately at 36-46F (2-8C). The reconstituted solution is stable for up to 28 days with bacteriostatic water.
Dilution Charts
3mg Vial
| BAC Water Added | Concentration | 0.25mg Dose | 1mg Dose |
|---|---|---|---|
| 1mL | 3,000mcg/mL | 8.3 units (0.083mL) | 33 units (0.33mL) |
| 1.5mLRecommended | 2,000mcg/mL | 12.5 units (0.125mL) | 50 units (0.5mL) |
| 2mL | 1,500mcg/mL | 16.7 units (0.167mL) | 67 units (0.67mL) |
5mg Vial
| BAC Water Added | Concentration | 0.25mg Dose | 2.4mg Dose |
|---|---|---|---|
| 1mL | 5,000mcg/mL | 5 units (0.05mL) | 48 units (0.48mL) |
| 2mLRecommended | 2,500mcg/mL | 10 units (0.1mL) | 96 units (0.96mL) |
| 3mL | 1,667mcg/mL | 15 units (0.15mL) | 144 units (1.44mL) |
Why 2mL? It keeps every dose in the standard escalation protocol measurable on a standard insulin syringe. At 2mL in a 5mg vial, even the maximum 2.4mg dose is only 96 units — comfortably within the 100-unit syringe.
The Math (So You Can Do It Yourself)
Here's the formula for any vial size and any amount of water:
Concentration = Peptide Amount (mcg) / Water Added (mL)
Then to find your 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 — fits perfectly in a 1mL syringe.
Don't want to do math? Use our Reconstitution Calculator — plug in your vial size, water amount, and desired dose, and it does the rest.
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Common Mistakes
Shaking the Vial
Peptides are proteins. Shaking creates foam, which means air bubbles trapped against peptide molecules. This can denature (destroy) the peptide at the air-liquid interface. Always swirl gently.
Using Too Little Water
Adding 0.5mL to a 5mg vial gives you 10,000mcg/mL. That means a 0.25mg starting dose is only 2.5 units — nearly impossible to measure accurately on an insulin syringe. The tiny tick marks become your enemy. Use at least 1mL, ideally 2mL.
Not Planning for the Full Escalation
Semaglutide protocols escalate from 0.25mg to 2.4mg weekly over several months. If you reconstitute with too much water, higher doses require injection volumes that exceed a single syringe. At 2mL per 5mg vial, every dose from start to maximum fits in one draw.
Leaving It at Room Temperature
Reconstituted semaglutide degrades rapidly above refrigerator temperature. Every hour at room temperature reduces potency. Pull the vial out, draw your dose, put it back. Don't leave it on the counter while you prep.
Reusing Needles
Each puncture through the rubber stopper dulls the needle and increases contamination risk. Fresh syringe every time — they cost pennies.
Freezing Reconstituted Peptide
Freezing a liquid peptide solution creates ice crystals that can shear the peptide bonds apart. Only freeze lyophilized (powder) peptides. Once reconstituted, refrigerate — never freeze.
How Many Doses Per Vial?
This depends on your dose escalation phase:
3mg vial:
- At 0.25mg/week = 12 weeks
- At 0.5mg/week = 6 weeks
- At 1mg/week = 3 weeks
- At 2.4mg/week = 1.25 weeks
5mg vial:
- At 0.25mg/week = 20 weeks
- At 0.5mg/week = 10 weeks
- At 1mg/week = 5 weeks
- At 1.7mg/week = ~3 weeks
- At 2.4mg/week = ~2 weeks
A 5mg vial can cover the entire first 4 months of a slow escalation protocol if you start at 0.25mg. At maintenance doses of 1.7-2.4mg, plan on one 5mg vial every 2-3 weeks.
Storage Quick Reference
| State | Temperature | Shelf Life |
|---|---|---|
| Lyophilized (powder) | Room temp | 6-12 months |
| Lyophilized (powder) | Refrigerated | 2+ years |
| Lyophilized (powder) | Frozen (-20C) | 3+ years |
| Reconstituted (BAC water) | Refrigerated | Up to 28 days |
| Reconstituted (sterile water) | Refrigerated | Use within 24 hours |
Pro tip: If you buy multiple vials, keep unopened ones in the freezer and only reconstitute what you'll use within 3-4 weeks.
Related Reading
-
Semaglutide Dosing Guide — titration schedules and protocols
-
Semaglutide Bloodwork Guide — what labs to track and optimal ranges
-
Retatrutide Reconstitution Guide — mixing guide for the triple-receptor agonist
-
Retatrutide Bloodwork Guide — biomarker tracking for the next-gen incretin
-
BPC-157 Reconstitution Guide — the standard reconstitution reference
-
MOTS-C Reconstitution Guide — mixing guide for the mitochondrial peptide
References
- Wilding, J.P.H., et al. (2021). Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine, 384(11), 989-1002. PMID:33567185
- Davies, M., et al. (2021). Semaglutide 2.4 mg once a week in adults with overweight or obesity, and type 2 diabetes (STEP 2). The Lancet, 397(10278), 971-984. PMID:33667417
- Goldenberg, R.M., et al. (2022). Once-weekly semaglutide for weight management: a clinical review. Journal of Pharmacy & Pharmaceutical Sciences, 25, 203-214. PMC9272494
- USP General Chapter 797: Pharmaceutical Compounding — Sterile Preparations. Storage and beyond-use dating guidelines for reconstituted peptides.
This guide is for educational and informational purposes only. It is not medical advice. Research-grade semaglutide is sold as a research compound. Reconstituting and self-administering peptides carries inherent risks including infection, contamination, and dosing errors. Always use proper sterile technique. Consult a qualified healthcare provider before starting any peptide protocol. The Peptide Catalog is not responsible for any adverse effects resulting from the use or misuse of information presented here.