How much bacteriostatic water for a 3mg Semaglutide vial?
Answer
Add 1.5 mL of bacteriostatic water to a 3 mg Semaglutide vial. That gives 2 mg/mL, so a 1 mg dose is 50 units on a U-100 insulin syringe. Note: a "3 mL bottle" almost always means a 3 mg vial. The glass itself is usually 3 mL.
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Bacteriostatic water options for a 3 mg vial
| Water added | Concentration | Units for 1 mg | Doses per vial |
|---|---|---|---|
| 0.5 mL | 6 mg/mL | 16.7 | 3 |
| 1 mL | 3 mg/mL | 33.3 | 3 |
| 1.5 mL ← recommended | 2 mg/mL | 50 | 3 |
| 2 mL | 1.5 mg/mL | 66.7 | 3 |
| 2.5 mL | 1.2 mg/mL | 83.3 | 3 |
| 3 mL | 1 mg/mL | 100 | 3 |
The recommended volume is the one that puts your dose on a clean syringe marking without filling the whole barrel.
Dose chart: 3 mg vial in 1.5 mL
| Dose | Volume | U-100 units | U-40 units | Doses per vial |
|---|---|---|---|---|
| 0.125 mg | 0.063 mL | 6.3 | 2.5 | 24 |
| 0.25 mg | 0.125 mL | 12.5 | 5 | 12 |
| 0.5 mg | 0.25 mL | 25 | 10 | 6 |
| 1 mg | 0.5 mL | 50 | 20 | 3 |
| 1.7 mg | 0.85 mL | 85 | 34 | 1 |
| 2 mg | 1 mL | 100 | 40 | 1 |
Doses that would need more than a full 1 mL syringe are omitted. Use less bacteriostatic water for those.
Common questions
- Does a "3 mL bottle" mean the same thing as a 3 mg vial?
- Almost always, yes. People say "mL" when they mean the amount of peptide, which is measured in mg. The glass vial itself is usually 3 mL regardless of whether it holds 3 mg or any other amount. The number on the label is milligrams of Semaglutide.
- What happens if I add more or less water than recommended?
- Nothing bad. You get the same total amount of peptide at a different concentration, so you draw a different number of units for the same dose. More water means a larger, easier-to-measure draw; less water means a smaller one.
- How many units is a 1 mg dose?
- At 1.5 mL of bacteriostatic water, a 3 mg vial is 2 mg/mL, so 1 mg is 0.5 mL, which is 50 units on a U-100 insulin syringe.
- Can I use sterile water instead of bacteriostatic water?
- No. Sterile water has no preservative, so a multi-dose vial mixed with it has to be used immediately. Bacteriostatic water contains 0.9% benzyl alcohol, which is what makes 28–60 day refrigerated storage possible.
Run your own numbers
These figures assume the vial and water volumes named above. Change either one and the units change with it.