How to reconstitute peptides: a complete step-by-step guide
Peptide reconstitution is the step most people get wrong. Bacteriostatic water, sterile technique, dose math, storage — here's the evidence-based walkthrough.
Peptide reconstitution is the step where most avoidable mistakes happen. The chemistry is simple. The procedure is straightforward. The math is elementary. What trips people up is ambiguity about sterile technique, the volume of bacteriostatic water to use, and how to turn a vial's mg into a syringe's units.
What bacteriostatic water is and why it's the correct diluent#
Bacteriostatic water (BAC water) is sterile water preserved with 0.9% benzyl alcohol. The alcohol prevents bacterial growth across the 28-day window that most lyophilised peptides stay stable once reconstituted and refrigerated.
Sterile water (without the benzyl alcohol) is an alternative, but it's single-use. After the first draw from a sterile-water vial, there's no antimicrobial defence against introduced bacteria, and the remaining solution should be discarded. That's wasteful for a peptide you dose two or three times a week.
Saline (0.9% sodium chloride) is used by some protocols but adds ions that can change peptide stability for some compounds. BAC water is the default for a reason: predictable behaviour, predictable shelf-life, minimal interaction.
The 28-day rule comes from USP sterility data showing that benzyl-alcohol preservative efficacy begins to degrade measurably after roughly four weeks of refrigerated use, even under correct sterile technique. If a reconstituted vial has been in the refrigerator longer than that, discard it and start fresh.
The five-step reconstitution procedure#
Every reputable peptide reconstitution protocol converges on the same steps.
1. Prepare the workspace. Clean a surface. Have the peptide vial, the BAC water vial, an alcohol wipe, a sterile needle (18G or larger for drawing BAC water; smaller insulin syringe — typically 28–31G — for dosing), and a disposal container within reach.
2. Wipe both rubber stoppers. Swab the peptide vial's rubber stopper with a 70% isopropyl alcohol wipe and let it dry for 15–20 seconds. Do the same for the BAC water vial. This is non-negotiable.
3. Draw the chosen volume of BAC water into the syringe. Typical reconstitution volumes are 1 mL, 2 mL, or 3 mL. The choice sets the final concentration — see the math section below. Insert the needle through the stopper at a slight angle to avoid coring. Withdraw the target volume plus a small amount to account for air.
4. Transfer the BAC water into the peptide vial slowly. Angle the needle so the water runs down the vial wall rather than splashing onto the peptide powder. Splashing the powder directly can denature fragile peptides. Do not inject forcefully.
5. Let the vial rest. Do not shake. Peptides are protein-like structures; aggressive shaking can break the bonds and inactivate the molecule. Gentle swirling, or a 30–60 second rest at room temperature, is usually enough for the powder to dissolve completely. Once clear, refrigerate at 2–8 °C.
The math, broken down#
Reconstitution math is two equations. That's it.
Concentration equation:
concentration (mcg/mL) = peptide in vial (mcg) ÷ BAC water volume (mL)
Syringe-unit equation (for a standard 1 mL insulin syringe, where 100 units = 1 mL):
units to draw = target dose (mcg) ÷ concentration (mcg/mL) × 100
Worked example#
A vial contains 5 mg (5,000 mcg) of BPC-157. You add 2 mL of BAC water.
- Concentration = 5,000 mcg ÷ 2 mL = 2,500 mcg/mL
- For a 250 mcg dose: units = 250 ÷ 2,500 × 100 = 10 units on the insulin syringe
- For a 500 mcg dose: units = 500 ÷ 2,500 × 100 = 20 units
Why the BAC water choice matters#
A 5 mg vial reconstituted with 1 mL gives 5,000 mcg/mL — each 20-unit draw is 1,000 mcg. That's a concentrated solution where small errors produce large dose swings.
The same 5 mg vial reconstituted with 5 mL gives 1,000 mcg/mL — each 20-unit draw is 200 mcg. More dilute, more forgiving on measurement, but uses BAC water faster.
The practical default: reconstitute to a concentration where typical doses fall between 5 and 25 syringe units. Below 5 units is hard to measure accurately; above 25 units is wasting BAC water. The Syntho peptide calculator recommends a BAC volume for any vial size and target dose combination.
Sterile technique rules that matter most#
Three rules do the heaviest lifting:
- One draw, one needle. Re-using a needle across multiple draws risks introducing bacteria through a dulled tip. Change needles between draws, or at minimum between the BAC-water draw and the peptide draw.
- Stopper cleaning between draws. Every time you pierce the rubber stopper, wipe it first with alcohol. The 15–20 second air-dry matters — wet alcohol pushed into the vial isn't the same as cleaned rubber.
- No freezing, no direct light. Most reconstituted peptides are stable at 2–8 °C. Freezing breaks peptide bonds. Direct sunlight accelerates degradation. A labelled dose of the vial in the back of the fridge, not the door, is the right storage location.
Storage, labelling, and the 28-day rule#
Reconstituted peptides go straight into the refrigerator (2–8 °C) after the powder has dissolved. Syntho recommends a dedicated container inside the fridge to keep vials upright, away from raw food, and out of the door where temperature fluctuates most.
Label every reconstituted vial with the date of reconstitution. A small piece of tape with the date written in permanent marker is sufficient. At day 28, discard. If a vial is close to day 28 but the product isn't finished, that's a signal the reconstituted volume was too high for the dose schedule — next time, use less BAC water.
BAC water itself has its own shelf-life. Once a BAC water vial is punctured, it's good for 28 days refrigerated, same as a reconstituted peptide. The Syntho BAC water calculator estimates how many BAC water vials a given protocol needs over 12 weeks, so orders match consumption.
The one-sheet summary#
Print this or screenshot it. Every reconstitution follows the same frame.
- Clean workspace, wipe both stoppers.
- Decide on BAC water volume. Prefer one where typical doses fall between 5 and 25 syringe units.
- Draw BAC water with a larger needle, transfer into peptide vial gently against the glass wall.
- Rest the vial 30–60 seconds. Swirl, don't shake. Refrigerate once dissolved.
- Label with date. Discard at 28 days.
For the math on any specific peptide and dose, the peptide calculator runs the conversion in both directions — enter your vial size and target dose, get the BAC volume and syringe units. The titration calculator builds an escalation schedule on top of that. Those two tools cover every reconstitution decision worth making.
Peptide protocols work when the foundation is tight. Reconstitution is the foundation.
Keep reading
Bacteriostatic water: why it matters and how much to use
Bacteriostatic water is the 0.9% benzyl-alcohol diluent that keeps reconstituted peptides stable for 28 days. Here's the chemistry, the volumes, and the math.
BPC-157 + TB-500 stack: what the evidence actually says
The BPC-157 + TB-500 stack is the most common healing peptide protocol. Here's the mechanism rationale, the dosing framework, and what the evidence does — and doesn't — support.
Peptide dosing math: mcg, mg, IU, and syringe units explained
Peptide dose math is simple once you separate the three unit systems. Here's how mcg, mg, and IU relate — and how to read them off an insulin syringe.