How much BAC water do I add to reconstitute a peptide?

The amount of BAC water depends on your peptide vial size and target dose. The goal is a draw amount of 10-50 units on a U-100 insulin syringe per dose. Formula: BAC water (ml) = (dose_mcg x desired_units) / (total_mcg x 100). For a 5mg BPC-157 vial dosed at 250mcg wanting a 10-unit draw: (250 x 10) / (5000 x 100) = 0.005 ml per unit x 100 units = 2ml BAC water. Use the free calculator at protocolapp.health/tools/reconstitution-calculator for automatic results.

What is bacteriostatic water and why is it used for peptide reconstitution?

Bacteriostatic water (BAC water) is sterile water containing 0.9% benzyl alcohol. The benzyl alcohol acts as a preservative, inhibiting bacterial growth in the reconstituted solution. This extends shelf life to 4-6 weeks refrigerated, compared to 1-2 days with plain sterile water. It is the standard diluent for injectable peptides. Never use tap water, saline, or distilled water.

How do I calculate peptide dose in syringe units?

Use this formula: Draw Units = (dose_mcg / total_mcg_in_vial) x (BAC_water_ml x 100). Example: 250mcg dose from a 5mg (5,000mcg) vial reconstituted with 2ml BAC water = (250/5000) x (2x100) = 0.05 x 200 = 10 units. On a U-100 insulin syringe, 10 units = 0.1ml. The reconstitution calculator at protocolapp.health does this math automatically.

How long does reconstituted peptide last in the fridge?

Peptides reconstituted with bacteriostatic water remain stable for 4-6 weeks when stored refrigerated at 2-8°C and protected from light. Peptides reconstituted with plain sterile water should be used within 1-2 days. Always discard if the solution appears cloudy, discolored, or has visible particles. Never freeze the reconstituted liquid -- only the lyophilized powder can be frozen.

Can you mix two peptides in the same syringe?

Yes, many peptide combinations are commonly mixed in the same syringe just before injection -- the most popular being CJC-1295 + Ipamorelin and BPC-157 + TB-500. Reconstitute each peptide separately, then draw each dose into the same syringe immediately before injection. Do not pre-mix or store combined solutions. Some combinations may be pH-incompatible -- research specific pairs before mixing.

Research/Articles/How to Reconstitute Peptides

ReconstitutionStep-by-Step GuideUpdated May 2026

How to Reconstitute Peptides: Step-by-Step Guide with Calculator

Q: How do you reconstitute a peptide?

To reconstitute a peptide: (1) Calculate how much BAC water to add using the reconstitution formula or a calculator. (2) Draw that amount of bacteriostatic water into a syringe. (3) Insert the needle into your peptide vial and slowly inject the BAC water down the inner vial wall -- never onto the powder directly. (4) Gently swirl until fully dissolved -- never shake. (5) Store refrigerated and use within 4-6 weeks.

Peptide reconstitution is the process of dissolving lyophilized (freeze-dried) peptide powder into bacteriostatic water to create an injectable solution. Get the math wrong and you are under- or over-dosing. This guide covers the formula, the process, and the exact numbers for 10 common compounds.

Free Reconstitution Calculator

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What Do You Need to Reconstitute a Peptide?

Lyophilized peptide vial

Your peptide in powder form. Check the label for total mg.

Bacteriostatic water (BAC water)

Sterile water with 0.9% benzyl alcohol preservative. Not tap water, not saline.

U-100 insulin syringes

28-31 gauge, 0.5ml or 1ml. One for drawing BAC water, one for injecting.

Alcohol swabs

To clean vial stoppers before every needle insertion.

Why BAC water specifically: Plain sterile water has no preservative. Once a peptide vial is punctured and air enters, bacteria can grow. BAC water's benzyl alcohol prevents this, extending the reconstituted peptide's shelf life from 1-2 days to 4-6 weeks refrigerated. This is non-negotiable for any peptide you will use across multiple doses.

The Reconstitution Formula Explained

The goal is to add enough BAC water so that your target dose falls between 10 and 50 units on a U-100 insulin syringe. Under 10 units is hard to measure accurately. Over 50 units means a large injection volume that can be uncomfortable.

The Formula

Draw Units = (dose_mcg ÷ total_mcg) × (BAC_water_ml × 100)

Where: total_mcg = vial_mg × 1,000

Example — BPC-157 5mg vial, 250mcg dose, 2ml BAC water:

total_mcg = 5mg × 1,000 = 5,000mcg

Draw = (250 ÷ 5,000) × (2 × 100)

Draw = 0.05 × 200

Draw = 10 units ✓ (ideal range)

The formula works in reverse too. If you know you want a specific draw amount, you can solve for the BAC water volume: BAC_water_ml = (draw_units × total_mcg) ÷ (dose_mcg × 100)

Or skip the math entirely — the reconstitution calculator does all of this automatically for any compound, vial size, and dose.

How to Reconstitute a Peptide: Step by Step

Calculate your BAC water amount

Use the reconstitution formula above or open the calculator. For BPC-157 at 250mcg from a 5mg vial, 2ml BAC water gives a 10-unit draw. For 500mcg from the same vial, 2ml still works — you draw 20 units instead.

Clean your workspace and vial stoppers

Wash hands. Wipe the top of both vials (BAC water vial + peptide vial) with an alcohol swab. Let air dry 30 seconds. A clean stopper prevents contamination on every future puncture.

Draw the BAC water

Insert your syringe needle into the BAC water vial. Pull back the plunger to draw your calculated amount. If you need 2ml and have a 1ml syringe, draw twice and transfer to the peptide vial in two steps — or use a 3ml or 5ml drawing syringe.

Add BAC water to the peptide vial slowly

Insert the needle into the peptide vial stopper. Tilt the vial slightly and angle the needle so the water flows down the inside wall of the glass — not directly onto the powder. Inject slowly. Pushing water forcefully onto the peptide cake can denature (break) the peptide chains.

Swirl gently — never shake

Once the BAC water is in, remove the needle and gently rotate the vial between your palms. Never shake — shaking creates bubbles and can mechanically damage the peptide. The powder should fully dissolve in 30-60 seconds. The final solution should be completely clear.

Store refrigerated and label the date

Cap the vial with the needle removed. Store in the fridge at 2-8°C away from direct light. Write the reconstitution date on the vial. With BAC water, it is stable for 4-6 weeks. In Protocol, log your reconstitution so the app tracks doses remaining and flags when to replace the vial.

Reconstitution Reference: 10 Common Peptides

Calculated for a 10-20 unit draw on a U-100 syringe. Use the calculator for custom vial sizes and doses.

Compound	Vial	Dose	BAC Water	Draw	Doses/Vial	Notes
BPC-157	5mg	250mcg	2ml	10 units	20 doses/vial	Standard starting protocol
BPC-157	5mg	500mcg	2ml	20 units	10 doses/vial	Higher loading dose
TB-500	5mg	2.5mg	2ml	50 units	2 doses/vial	Twice weekly loading
TB-500	10mg	2.5mg	4ml	50 units	4 doses/vial	Full loading cycle supply
Ipamorelin	5mg	300mcg	2.5ml	15 units	16 doses/vial	2x daily protocol
CJC-1295	2mg	100mcg	1ml	5 units	20 doses/vial	Stack with Ipamorelin
Semaglutide	3mg	0.25mg	1.5ml	12.5 units	12 doses/vial	Starting titration dose
Tirzepatide	5mg	2.5mg	2ml	50 units	2 doses/vial	Starting titration dose
GHK-Cu	50mg	1mg	5ml	10 units	50 doses/vial	High vial size — larger supply
GHK-Cu	50mg	2mg	5ml	20 units	25 doses/vial	Higher dose protocol

Common Reconstitution Mistakes to Avoid

Avoid

Shaking the vial

Fix: Swirl gently. Shaking creates bubbles and can mechanically break peptide chains.

Avoid

Injecting BAC water directly onto the powder

Fix: Angle the needle so water runs down the vial wall. Direct injection can denature the peptide.

Avoid

Using saline, tap water, or sterile water

Fix: Saline can cause peptide precipitation. Tap water is not sterile. Sterile water has no preservative — 24-48 hour shelf life only.

Avoid

Freezing the reconstituted solution

Fix: Only lyophilized powder can be frozen. Freeze-thaw cycles damage reconstituted peptide. The fridge is the right storage location.

Avoid

Not labeling the reconstitution date

Fix: Without a date, you cannot track the 4-6 week stability window. Always write the date on the vial.

Avoid

Drawing under 5 or over 50 units per dose

Fix: Under 5 units is too small to measure accurately. Over 50 units is a large injection volume. Adjust BAC water to land in the 10-30 unit sweet spot.

Frequently Asked Questions

How do you reconstitute a peptide?

Calculate your BAC water amount using the reconstitution formula or calculator. Draw that amount into a syringe. Inject it slowly down the inside wall of the peptide vial. Swirl gently until dissolved. Store refrigerated and use within 4-6 weeks.

How much BAC water do I add to my peptide?

Enough to make your per-dose draw land between 10-50 units on a U-100 syringe. For a 5mg BPC-157 vial at 250mcg per dose, 2ml BAC water gives a 10-unit draw. The free calculator at protocolapp.health/tools/reconstitution-calculator gives exact numbers for any compound and dose.

What happens if I use too much or too little BAC water?

Too much BAC water = very dilute solution = large draw per dose (over 50 units becomes uncomfortable to inject). Too little BAC water = very concentrated = tiny draw per dose (under 5-10 units is hard to measure accurately). Both are usable but not optimal. The calculator helps you find the ideal concentration.

Can I reconstitute with sterile water instead of BAC water?

Technically yes, but the reconstituted peptide will only last 1-2 days refrigerated without BAC water's benzyl alcohol preservative. For any compound you will use across multiple doses over days or weeks, BAC water is required.

Reconstitution Calculator

Get exact BAC water volumes and draw units for 45+ compounds. Free, instant, no signup.

BPC-157 Dosing Guide

250-500mcg dosing, local vs systemic injection, arginate vs acetate, cycle length.

References

[1]United States Pharmacopeia. General Chapter <797> Pharmaceutical Compounding — Sterile Preparations. USP-NF. Rockville, MD: USP.
[2]Bhambhani A, Kissmann JM, Joshi S, et al. Formulation design and high-throughput excipient selection based on structural integrity and conformational stability of dilute and highly concentrated IgG1 monoclonal antibody solutions. J Pharm Sci. 2012;101(3):1120-1135.
[3]Lam XM, Duenas ET, Cleland JL. Encapsulation and stabilization of nerve growth factor into poly(lactic-co-glycolic) acid microspheres. J Pharm Sci. 2001;90(9):1356-1365.
[4]Mumenthaler M, Hsu CC, Pearlman R. Feasibility study on spray-drying protein pharmaceuticals: recombinant human growth hormone and tissue-type plasminogen activator. Pharm Res. 1994;11(1):12-20.

Citations are provided for informational context. This article does not reproduce copyrighted content from these sources.

Disclaimer: For informational purposes only. Not medical advice. Peptide use for human injection may be regulated in your jurisdiction. Consult a licensed healthcare provider before using any injectable compound.

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