How to reconstitute research peptides — bacteriostatic water, volumes, and U-100 syringe math
Reconstitution is the standard laboratory step between a lyophilised research-peptide vial and a usable solution for protocol administration. The procedure is straightforward but the math trips up first-time researchers — vial mass in milligrams, diluent volume in millilitres, dose in micrograms, syringe markings in U-100 units. This reference walks through the variables and links the free interactive calculator at /tools/reconstitution-calculator.
What bacteriostatic water actually is
Bacteriostatic water for injection (BAC) is sterile water with 0.9% benzyl alcohol added as a preservative. The benzyl alcohol inhibits bacterial growth in the vial after the rubber stopper is punctured by a needle, allowing the reconstituted vial to be re-entered repeatedly (typically up to ~28 days at 2-8°C) without contamination concerns.
Two practical notes:
- BAC vs sterile water. Plain sterile water has no preservative and is intended for single-entry use. For research-peptide reconstitution, BAC is the standard diluent because the vial is typically re-entered across multiple research-protocol administrations.
- BAC vs acetic acid water. Some peptides have poor aqueous solubility and require dilute acetic acid (0.6% v/v) instead of BAC. The product specification or COA will note this. Most common research peptides reconstitute cleanly in BAC.
The reconstitution math
Three variables, two simple conversions:
- Vial mass (mg). Stated on the COA and the vial label.
- Diluent volume (mL). Your choice. Common values: 1 mL, 2 mL, 2.5 mL, 5 mL.
- Dose (μg). Specified by the research protocol.
Step 1 — concentration. Divide vial mass by diluent volume.
Concentration (mg/mL) = vial mg ÷ diluent mL. Convert to μg/mL by multiplying by 1000.
Example: 5 mg vial + 2 mL BAC = 2.5 mg/mL = 2500 μg/mL.
Step 2 — dose volume. Divide dose by concentration.
Dose volume (mL) = dose μg ÷ concentration μg/mL.
Example: 250 μg dose at 2500 μg/mL = 0.1 mL.
Step 3 — U-100 syringe units. Multiply mL by 100.
U-100 units = mL × 100.
Example: 0.1 mL = 10 units on a U-100 insulin syringe.
The whole calculation is one line: dose μg ÷ vial μg × diluent mL × 100 = units. The interactive calculator at /tools/reconstitution-calculator does this automatically and runs the math against the SKUs in the Wellness Labs catalogue.
Choosing the diluent volume
The choice of diluent volume affects the units-per-dose math and the practical workflow. Trade-offs:
- Lower diluent volume = higher concentration = fewer syringe units per dose. Useful when small-volume draws are preferred or when storage space is limited.
- Higher diluent volume = lower concentration = more syringe units per dose. Useful when the dose-volume needs to be a draw-line readable to the nearest unit. Most insulin syringes (U-100, 30u or 50u or 100u sizes) read in 1-unit or 2-unit increments; very small draws (1-2 units) are harder to measure precisely.
- Practical sweet spot. Most published protocols use a diluent volume that puts the typical dose somewhere in the 10-30 unit range — comfortable on a 30-unit U-100 syringe.
Storage and shelf-life
The reconstitution procedure
- Bring both vials to room temperature. Cold vials produce condensation that can interfere with the rubber stopper seal.
- Wipe both rubber stoppers with isopropyl-alcohol pad. The 70% IPA pad standard in laboratory supply is appropriate.
- Draw the diluent volume into a syringe. A larger-volume syringe (3-5 mL) is convenient for this step.
- Insert the syringe at a 45° angle into the peptide vial, with the needle tip against the inside vial wall (not pointed at the lyophilised pellet). This avoids spraying the powder.
- Slowly inject the diluent down the inside wall of the vial. The peptide will dissolve as the water contacts it.
- Do NOT shake vigorously. Gentle swirling or gentle inversion is sufficient. Vigorous shaking can denature some peptides; foaming traps peptide at the air-water interface.
- Wait 1-5 minutes for full dissolution. The solution should be clear; cloudiness or visible particles indicates a problem.
- Label the reconstituted vial. Note the date of reconstitution, the diluent volume, and the resulting concentration.
- Store refrigerated (2-8°C) protected from light. Use within the protocol-specified shelf-life.
Common reconstitution mistakes
- Vigorous shaking. Common with first-time users. Gentle swirling is correct.
- Pointing the needle at the lyophilised pellet during injection. Causes spray and powder loss. Inject down the inside wall.
- Forgetting to label the reconstituted vial. The diluent volume is needed for every subsequent dose calculation; not noting it on the vial label means redoing the math.
- Storing reconstituted vials in the freezer. Freeze-thaw degrades peptides. Refrigerator only.
- Using non-BAC water for repeated-entry vials. Plain sterile water has no preservative; vial contamination risk increases on each subsequent entry.
Further reading
- Free reconstitution calculator — interactive dose-volume math for the Wellness Labs catalogue.
- Tesamorelin dosing protocols — worked reconstitution example.
- Sermorelin dosing protocols — frequent-dosing reconstitution example.
- GHK-Cu dosing — example of an alternative diluent system (copper-stable formulation).
Last reviewed 2 June 2026. Editorial inbox: info@uaewellnesslab.com.
Frequently asked questions
- What is bacteriostatic water?
- Sterile water for injection with 0.9% benzyl alcohol added as a preservative. The benzyl alcohol inhibits bacterial growth in the vial after the rubber stopper is punctured, allowing the reconstituted vial to be re-entered repeatedly (typically up to ~28 days at 2-8°C) without contamination concerns. It is the standard diluent for research-peptide reconstitution.
- How do I calculate the dose volume?
- Three steps. Step 1 — concentration: divide vial mass (mg) by diluent volume (mL) to get mg/mL, then multiply by 1000 to get μg/mL. Step 2 — dose volume: divide dose (μg) by concentration (μg/mL) to get mL. Step 3 — U-100 units: multiply mL by 100. Example: 5 mg vial + 2 mL BAC = 2500 μg/mL; 250 μg dose = 0.1 mL = 10 units.
- What is a U-100 insulin syringe?
- A syringe calibrated for U-100 insulin, where 100 units = 1 mL. The 30-unit, 50-unit, and 100-unit sizes share this calibration; they differ only in maximum draw volume. The U-100 unit system makes small-volume peptide draws practical — 10 units on the syringe = 0.1 mL.
- Should I shake the vial after adding water?
- No. Gentle swirling or gentle inversion is correct. Vigorous shaking can denature some peptides and foaming traps peptide at the air-water interface. Inject the water down the inside wall of the vial (not pointed at the lyophilised pellet), then swirl for 30-60 seconds until fully dissolved.
- How long does a reconstituted vial last?
- Approximately 28 days at refrigerated temperature (2-8°C) protected from light is typical for most research peptides. Specific peptides vary — glutathione-class compounds have shorter reconstituted shelf-life due to oxidation sensitivity; lipid-modified peptides like Tesamorelin are photosensitive. Never freeze reconstituted vials; freeze-thaw cycles degrade most peptides.