How Peptide Reconstitution Works
Peptide reconstitution is the process of dissolving a lyophilized (freeze-dried) peptide powder into bacteriostatic water (BAC water) to create an injectable solution. The powder is measured in milligrams (mg) and the resulting solution is drawn in units using a standard U-100 insulin syringe, where 100 units equals 1 milliliter.
The amount of BAC water you add determines the concentration of your solution. More BAC water produces a less concentrated solution with larger draw volumes per dose — easier to measure precisely. Less BAC water produces a more concentrated solution with smaller draws — useful when you prefer less injection volume or when the compound causes discomfort at the injection site.
For example: a 5 mg vial of BPC-157 dosed at 250 mcg per injection yields 20 doses per vial. Adding 2 ml of BAC water creates a concentration of 2,500 mcg/ml, meaning each 250 mcg dose requires drawing 10 units (0.1 ml) on a U-100 syringe. Enter your numbers below and the calculator does this math instantly.
Reconstitution Calculator
Exact BAC water volumes and draw units for any peptide. Set your vial size and slide to your preferred concentration.
mg of powder in the vial
physical bottle capacity
Enter peptide amount and target dose to see reconstitution options.
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Download Protocol Free on iOSStep-by-Step Reconstitution Guide
A general guide for reconstituting injectable peptides. Always follow sterile technique.
- 1
Calculate your BAC water amount
Use the calculator above. Enter your peptide amount (mg), vial volume (ml), and target dose. The concentration slider shows you exactly how much BAC water to add — slide left for a smaller, more precise draw; slide right for a larger, easier-to-measure draw.
- 2
Prepare your workspace
Wash hands thoroughly. Wipe all vial tops with an alcohol swab — both the BAC water vial and your peptide vial. Allow to air dry for 30 seconds.
- 3
Draw the BAC water
Insert your syringe into the BAC water vial and withdraw the calculated amount. For example, if the calculator shows 2 ml, draw to the 200-unit mark on a 1 ml syringe, or use a larger drawing syringe for volumes over 1 ml.
- 4
Add water to the peptide vial slowly
Insert the needle into your peptide vial. Angle the tip so BAC water runs gently down the inside wall of the vial — not directly onto the powder cake. Inject slowly. Never force the liquid.
- 5
Allow the powder to dissolve
Gently swirl (do not shake) the vial until the powder fully dissolves. The solution should be completely clear. If you see any cloudiness or particles, do not use.
- 6
Store and log your reconstitution
Store the vial in the refrigerator. Write the date on the vial. In Protocol, you can log your reconstitution details so the app automatically calculates your draw units at each dose.
Common Peptide Reconstitution Reference
Typical starting points for popular peptides. Individual protocols vary — always follow your specific dosing guidance and use the calculator above for exact values.
| Compound | Common Vial | Typical Dose | BAC Water | Draw (units) |
|---|---|---|---|---|
| BPC-157 | 5 mg | 250 mcg | 2 ml | 10 units |
| TB-500 | 5 mg | 2.5 mg | 2 ml | 50 units |
| GHK-Cu | 50 mg | 1 mg | 5 ml | 10 units |
| KPV | 10 mg | 300 mcg | 2 ml | 6 units |
| CJC-1295 | 2 mg | 100 mcg | 1 ml | 5 units |
| Ipamorelin | 5 mg | 300 mcg | 2.5 ml | 15 units |
| Semaglutide | 3 mg | 0.25 mg | 1.5 ml | 12.5 units |
| Tirzepatide | 5 mg | 2.5 mg | 2 ml | 50 units |
| Epithalon | 10 mg | 5 mg | 2 ml | 100 units |
| Selank | 5 mg | 250 mcg | 2 ml | 10 units |
Use the calculator above to get exact values for your specific vial size and dose. These are common starting points, not medical recommendations.
Frequently Asked Questions
What is bacteriostatic water and why do I need it?
Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol, which inhibits bacterial growth. It's the standard diluent for injectable peptides because it preserves the reconstituted solution for 4–6 weeks when stored refrigerated. Sterile water (without preservative) can be used, but the solution should typically be used within a few days. Never use tap water or saline for peptide reconstitution.
How much BAC water should I add to my peptide vial?
The amount depends on your dose and how many units you want to draw per injection. More BAC water means a more diluted solution and a larger draw per dose (easier to measure). Less BAC water means a more concentrated solution and a smaller draw. For most peptides, 1–3 ml of BAC water per vial produces draw amounts between 5 and 50 units — the easiest range to measure accurately with a U-100 insulin syringe. Use the calculator above to find the exact amount for your vial and dose.
What syringe do I use for peptide injections?
The standard syringe for peptide injections is a U-100 insulin syringe (also called a 1 ml insulin syringe). These are calibrated in units where 100 units = 1 ml = 1 cc. They're available in 0.5 ml (50-unit) and 1 ml (100-unit) sizes. Most peptide doses fall between 5 and 50 units, so either size works. The fine 28–31 gauge needles make subcutaneous (subQ) injections nearly painless.
How do I convert mcg to units on a syringe?
The conversion depends on your reconstitution concentration. The formula is: Draw Units = (Dose in mcg ÷ Total mcg in vial) × (BAC water in ml × 100). For example: 5 mg vial (5,000 mcg) reconstituted with 2 ml BAC water, dosing 250 mcg → (250 ÷ 5,000) × (2 × 100) = 10 units. The calculator on this page does this math automatically for any compound, vial size, and dose.
How long does reconstituted peptide last?
Reconstituted peptides stored in the refrigerator (2–8°C) with bacteriostatic water typically remain stable for 4–6 weeks. Keep vials away from light and avoid temperature fluctuations. Never freeze a reconstituted peptide solution — lyophilized powder can be frozen, but not the liquid. Discard any solution that appears cloudy, discolored, or has visible particles.
How do I add BAC water to a peptide vial without damaging it?
Draw the desired amount of BAC water into your syringe. Insert the needle into the peptide vial at an angle so the liquid runs down the inside of the vial wall rather than directly onto the powder. Never inject the water forcefully onto the peptide cake — this can denature (damage) the peptide. Gently swirl the vial — never shake it. Allow a minute or two for the powder to fully dissolve. The solution should be completely clear.
What's the difference between subcutaneous and intramuscular injection for peptides?
Subcutaneous (subQ) injections go into the fat layer just below the skin — the belly, love handles, or outer thigh are common sites. This is the standard method for most peptides including BPC-157, GHK-Cu, and most GLP-1 analogs. Intramuscular (IM) injections go directly into muscle tissue and may produce faster absorption for certain compounds. For subQ injections, pinch the skin and insert a 28–31 gauge needle at a 45-degree angle. Most peptide users prefer subQ for convenience and comfort.
Can I mix two peptides in the same syringe?
Some peptides are commonly stacked together in a single injection — for example, CJC-1295 and Ipamorelin are often combined. To mix, reconstitute each peptide separately, then draw your dose of one peptide followed by your dose of the second into the same syringe just before injection. Do not pre-mix peptides in a single vial for storage. Some peptides should not be combined due to pH incompatibility or competing mechanisms — research specific combinations before mixing.