How Much BAC Water to Use
The simple math behind concentration, with reference tables and syringe units.
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Getting started
How to Reconstitute Peptides: A Step-by-Step Guide
Turn a vial of freeze-dried powder into a usable research solution in about two minutes. Here's exactly how — what you need, how to mix it, and how to store it.
If you've just received a vial of lyophilized (freeze-dried) peptide, reconstitution is the step that turns that powder into a usable solution for your research. It looks intimidating the first time, but it's simple, takes about two minutes, and uses just a few basic supplies. This applies to virtually any research peptide supplied in lyophilized form — semaglutide, tirzepatide, retatrutide, BPC-157, TB-500, and others.
Research use only. This article is an educational
overview of laboratory reconstitution procedure. It is not medical advice and does not
describe human use.
What you'll need
| Item | Why |
|---|---|
| Lyophilized peptide vial | The freeze-dried powder you're reconstituting |
| Bacteriostatic water | The solvent — its benzyl alcohol keeps the solution stable for weeks |
| Insulin syringes | To draw the BAC water and measure your solution |
| Alcohol wipes | To clean the rubber stoppers before piercing |
Bacteriostatic water is the standard solvent because the benzyl alcohol preservative lets a reconstituted peptide keep for weeks in the fridge — unlike sterile or distilled water, which has no preservative.
Step-by-step reconstitution
1. Let everything reach room temperature. If your peptide was shipped cold, give the vial a few minutes out of the fridge. Cold vials can cause condensation.
2. Clean both stoppers. Wipe the rubber top of the peptide vial and the BAC water vial with an alcohol wipe and let them dry.
3. Draw your BAC water. Using an insulin syringe, draw the amount you've decided on (see below). A common starting point is 2 mL per vial.
4. Add the water slowly — down the side of the glass. Let it run slowly down the inside wall of the vial, not directly onto the powder. The peptide is fragile.
5. Do NOT shake. Swirl gently. Gently swirl or roll the vial between your fingers. Shaking can denature the peptide. Within a minute or two the powder fully dissolves into a clear solution.
6. Label and refrigerate. Note the date and concentration on the vial, and store it in the refrigerator. Done — the vial is reconstituted and stable.
The single most common mistake is shaking the vial. Always swirl gently — peptides are fragile.
How much BAC water should I use?
The amount of BAC water you add determines the concentration of your solution. More water = more diluted; less water = more concentrated. The math is simple:
Concentration (mg/mL) = peptide (mg) ÷ BAC water added (mL)
Example: a 10 mg vial with 2 mL of BAC water gives 10 ÷ 2 = 5 mg/mL. Quick reference for a 10 mg vial:
| BAC water added | Resulting concentration |
|---|---|
| 1 mL | 10 mg/mL |
| 2 mL | 5 mg/mL |
| 5 mL | 2 mg/mL |
Want the full breakdown plus how to read syringe units? See How Much BAC Water to Use.
How to store reconstituted peptides
- Before reconstitution: keep the sealed vial cool, dry, and out of direct light.
- After reconstitution: store in the refrigerator (not the freezer). With BAC water, it typically stays stable for several weeks.
- Keep it out of direct light and avoid repeated temperature swings.
Common mistakes to avoid
- Shaking the vial. The most common error. Always swirl gently.
- Squirting water straight onto the powder. Run it down the glass wall.
- Using the wrong water. Sterile or distilled has no preservative — use bacteriostatic.
- Freezing the solution. Refrigerate, don't freeze.
- Not labeling. Always note the date and concentration.
Where to buy
Need bacteriostatic water & tested compounds?
We recommend Vital Chems — research-grade supplies, shipped fast.
- Third-party HPLC tested — COA on every order
- Same-day shipping before 1:30 PM PT
- US-based, fast and responsive support
Frequently asked questions
Do all peptides need to be reconstituted?
Any peptide supplied as a lyophilized (freeze-dried) powder needs reconstitution before use in solution. That covers the large majority of research peptides.
Can I use sterile or distilled water instead of BAC water?
You can dissolve the powder with them, but the solution won't keep — they have no preservative. Bacteriostatic water keeps it stable for weeks.
How long does a reconstituted peptide last?
Stored in the refrigerator, a solution made with bacteriostatic water generally stays stable for several weeks.
Why shouldn't I shake the vial?
Peptides are fragile chains of amino acids. The mechanical stress of shaking can denature them. Gentle swirling dissolves the powder without damaging it.