A semaglutide mixing chart shows the volume of bacteriostatic water needed to reconstitute a powder vial to a target concentration. For compounded semaglutide, the typical question is whether to mix a 5 mg vial to 2.5 mg/mL (add 2 mL water) or 5 mg/mL (add 1 mL water). The math is straightforward — final concentration equals total mg divided by total mL added — but the practical steps require care to avoid contamination and dosing errors.
Standard Mixing Chart
| Powder Vial Strength | Bacteriostatic Water Added | Final Concentration | Total Doses (at 0.25 mg) |
|---|---|---|---|
| 2 mg | 0.8 mL | 2.5 mg/mL | 8 doses |
| 2 mg | 0.4 mL | 5.0 mg/mL | 8 doses |
| 5 mg | 2.0 mL | 2.5 mg/mL | 20 doses |
| 5 mg | 1.0 mL | 5.0 mg/mL | 20 doses |
| 5 mg | 0.5 mL | 10.0 mg/mL | 20 doses |
| 10 mg | 4.0 mL | 2.5 mg/mL | 40 doses |
| 10 mg | 2.0 mL | 5.0 mg/mL | 40 doses |
| 10 mg | 1.0 mL | 10.0 mg/mL | 40 doses |
Note: total number of doses depends on the dose size. The table above shows starting-dose count (0.25 mg). Higher maintenance doses (2.4 mg) yield fewer total doses per vial.
The Math Behind Mixing
Concentration is total mg divided by total mL. Reconstitution does not add or remove semaglutide — it only dissolves the powder into water. So:
- 5 mg powder + 2 mL water = 5 mg ÷ 2 mL = 2.5 mg/mL
- 5 mg powder + 1 mL water = 5 mg ÷ 1 mL = 5 mg/mL
- 10 mg powder + 2 mL water = 10 mg ÷ 2 mL = 5 mg/mL
The math is simple; the failure modes are the procedural steps.
Why Bacteriostatic Water Matters
Bacteriostatic water for injection contains 0.9 percent benzyl alcohol as a preservative. The preservative prevents bacteria from growing in the vial once it has been punctured. Multi-dose vials are punctured many times over 4-6 weeks; without preservative, even sterile water can support bacterial growth between punctures.
Plain sterile water is NOT a substitute. The FDA has documented contamination cases where home-mixers used plain sterile water and developed infections from contaminated vials. Bacteriostatic water is widely available through pharmacies and is the standard.
Reconstitution Technique (Done by Pharmacy)
This should ideally be done by your licensed compounding pharmacy. If you receive a powder vial and bacteriostatic water with instructions to reconstitute, follow these general steps carefully:
- Wash hands thoroughly and prepare a clean work surface
- Wipe the rubber stoppers of both vials (powder and water) with alcohol pads
- Draw the specified amount of bacteriostatic water into a sterile syringe
- Insert the needle into the powder vial at an angle and slowly inject the water down the inside wall of the vial — do not blast directly onto the powder
- Gently swirl the vial (do not shake) until the powder fully dissolves; this can take 1-2 minutes
- Inspect the solution for clarity — discard if cloudy, discolored, or contains particles
- Label the vial with the new concentration, mixing date, and beyond-use date
- Store in the refrigerator at 36-46°F / 2-8°C
Shaking the vial vigorously damages the semaglutide peptide. Always swirl gently.
Why Letting the Pharmacy Mix Is Safer
FDA safety reports cite several home-mixing errors:
- Using the wrong volume of water (concentration error)
- Using plain sterile water instead of bacteriostatic (contamination risk)
- Shaking instead of swirling (peptide damage)
- Failing to label the new concentration (later dosing errors)
- Using non-sterile syringes or needles (contamination)
- Storing at incorrect temperature (peptide degradation)
Licensed compounding pharmacies have sterile conditions, validated procedures, and trained staff. Home mixing carries materially higher risk of contamination and dosing errors.
Beyond-Use Dating
Once reconstituted, compounded semaglutide has a beyond-use date (BUD) — the date after which the product should be discarded. Typical BUDs:
- Refrigerated, with preservative: 4-6 weeks (varies by pharmacy)
- Room temperature: 1-2 weeks or less
- Without preservative (plain sterile water): days only
Your pharmacy will provide the BUD for your specific product. Never use past the BUD; discard and request a refill.
Signs of Spoiled Reconstituted Semaglutide
Discard the vial if you see:
- Cloudiness or change in color (should be clear and colorless)
- Visible particles or sediment
- Bubbles or foam that don’t dissipate after gentle swirling
- Damage to the rubber stopper
- Date past the BUD
The Bottom Line
Semaglutide mixing is concentration math — total mg divided by total mL added equals the final concentration. The standard 5 mg vial reconstitutes to 2.5 mg/mL with 2 mL of bacteriostatic water, or to 5 mg/mL with 1 mL. Always use bacteriostatic water (not plain sterile water) and follow your pharmacy’s specific instructions exactly. The FDA has documented home-mixing errors; reconstitution by a licensed compounding pharmacy is safer. Consult your prescriber and pharmacist before mixing or injecting any compounded medication. For more on GLP-1 treatment options, see our hub.
