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

Reconstituting peptides is the essential first step before any research protocol can begin. Whether you’re working with BPC-157, TB-500, or any other lyophilized peptide, proper reconstitution ensures accurate dosing, preserves peptide integrity, and produces reliable results. This guide walks through the full process of how to reconstitute peptides, from gathering supplies to storing your finished solution. A peptide reconstitution calculator is also available to simplify the math.

All peptides discussed in this article are intended for research use only. Nothing in this guide constitutes medical advice.

What Is Peptide Reconstitution?

Peptides are typically sold as a lyophilized (freeze-dried) powder inside a sealed glass vial. In this form, they are shelf-stable and easy to ship. However, the powder cannot be measured accurately by weight for individual doses. Reconstitution is the process of dissolving that powder into a precise volume of sterile liquid — most commonly bacteriostatic water (bac water) — so that exact microgram doses can be drawn with an insulin syringe.

The resulting solution has a known concentration, measured in micrograms per milliliter (mcg/mL). Once you know the concentration, every dose becomes a simple volume calculation.

What You’ll Need

Before you begin, gather the following supplies in a clean workspace:

Item	Purpose
Lyophilized peptide vial	The research compound, sealed with a rubber stopper and flip-off cap
Bacteriostatic water (bac water)	Sterile water preserved with 0.9% benzyl alcohol; standard reconstitution solvent
Insulin syringes (0.5 mL or 1 mL)	For measuring and administering precise doses in research protocols in “units”
Alcohol swabs	To sterilize vial stoppers before each needle insertion
Mixing syringe (1—3 mL)	A larger syringe for transferring bac water into the peptide vial
Sharps container	Safe disposal of used sharps per laboratory safety standards

Where to get supplies: Shop bacteriostatic water and peptides at Peptide Restore — 5% off with code DKE4PDRM.

A Note on Solvents

Bacteriostatic water is the preferred solvent for most peptide reconstitution because the benzyl alcohol preservative inhibits bacterial growth, allowing multi-use access to the vial over days or weeks. Sterile water (without preservative) is an alternative but should be used within 24 hours of reconstitution. Some peptides — particularly those with poor water solubility — may require acetic acid or mannitol-based solvents. Always check the manufacturer’s data sheet for solvent recommendations.

Step-by-Step Reconstitution Process

Follow these steps carefully to ensure a clean, accurate reconstitution.

Step 1: Wash Your Hands and Prepare Your Workspace

Work on a clean, flat surface. Wash your hands thoroughly or wear nitrile gloves. Lay out all supplies so nothing needs to be retrieved mid-process.

Step 2: Remove the Flip-Off Cap

Pop the colored plastic cap off the peptide vial to expose the rubber stopper beneath. Do not remove the aluminum crimp ring — the stopper is designed to be pierced by a needle.

Step 3: Swab the Vial Stoppers

Use an alcohol swab to wipe the rubber stopper of both the peptide vial and the bacteriostatic water vial. Allow the alcohol to air-dry for a few seconds. This prevents contaminants from entering either vial.

Step 4: Draw the Desired Volume of Bacteriostatic Water

Using a clean mixing syringe, insert the needle into the bac water vial and draw out the volume you have chosen for reconstitution. Common volumes are 1 mL or 2 mL, though you can use any amount — the key is to record the exact volume so you can calculate concentration later.

Step 5: Inject Bac Water Into the Peptide Vial

Pierce the rubber stopper of the peptide vial and slowly inject the bacteriostatic water. Aim the stream against the glass wall of the vial, not directly onto the powder. Let the water trickle down the side and pool at the bottom. This gentle technique prevents degradation from excessive agitation or foaming. (Think of it like pouring a beer down the side of a glass — same idea.)

Step 6: Swirl Gently — Never Shake

Once the water is in the vial, tilt or gently roll the vial between your fingers until the powder dissolves completely. The solution should become clear. Do not shake the vial. Aggressive shaking can denature the peptide chains, reducing potency.

Step 7: Label the Vial

Write the peptide name, reconstitution date, concentration, and total volume on a small label or piece of tape and affix it to the vial. This prevents dosing errors if you have multiple vials in storage.

Step 8: Store Properly

Place the reconstituted vial in the refrigerator at 2—8 degrees Celsius (36—46 degrees Fahrenheit). For detailed guidance on shelf life and degradation, see our article on peptide storage and stability.

Understanding Concentrations

The concentration of your reconstituted peptide is determined by a simple formula:

Concentration (mcg/mL) = Total Peptide (mcg) / Volume of Bac Water (mL)

Example 1: 5 mg Vial with 2 mL Bac Water

• Convert milligrams to micrograms: 5 mg = 5,000 mcg
• Divide by volume: 5,000 mcg / 2 mL = 2,500 mcg/mL
• For a 250 mcg dose: 250 / 2,500 = 0.1 mL = 10 units on an insulin syringe

Example 2: 10 mg Vial with 2 mL Bac Water

• 10 mg = 10,000 mcg
• 10,000 mcg / 2 mL = 5,000 mcg/mL
• For a 500 mcg dose: 500 / 5,000 = 0.1 mL = 10 units

Example 3: 5 mg Vial with 1 mL Bac Water

• 5 mg = 5,000 mcg
• 5,000 mcg / 1 mL = 5,000 mcg/mL
• For a 250 mcg dose: 250 / 5,000 = 0.05 mL = 5 units

Notice how the volume of bac water you choose directly affects how many units you need to draw per dose. Using less water creates a more concentrated solution (fewer units per dose), while using more water creates a more dilute solution (more units per dose). Neither is inherently better — choose whichever makes your dosing volume convenient for your syringe.

Using a Peptide Reconstitution Calculator

Doing the math by hand is straightforward, but why risk a mistake? A peptide reconstitution calculator eliminates errors and saves time — especially when you’re working with multiple compounds at different concentrations.

Our free Peptide Reconstitution Calculator lets you:

• Enter the peptide amount (in mg) printed on your vial
• Enter the volume of bacteriostatic water you plan to add
• Enter your desired dose in mcg
• Instantly see the concentration and the exact number of syringe units to draw

This is particularly useful when adjusting doses across a research protocol or when switching between different vial sizes. Bookmark the calculator page and use it each time you reconstitute a new vial to verify your math.

Syringe Units Explained

Insulin syringes are calibrated in “units” rather than milliliters, which can be confusing at first. Here is how the conversion works:

• 1 mL = 100 units (on a standard U-100 insulin syringe)
• 0.1 mL = 10 units
• 0.01 mL = 1 unit

Most peptide dosing falls somewhere between 5 and 30 units, depending on the concentration you created during reconstitution.

Syringe Size Reference

Syringe Size	Total Volume	Total Units	Best For
0.3 mL (3/10 cc)	0.3 mL	30 units	Small doses, precise measurement
0.5 mL (1/2 cc)	0.5 mL	50 units	Most common for peptide research
1.0 mL (1 cc)	1.0 mL	100 units	Larger doses or dilute solutions

Reading the Syringe

Each small tick mark on a 1 mL syringe represents 1 unit (0.01 mL). On a 0.5 mL syringe, each tick mark also represents 1 unit, but the markings are more spread out, making them easier to read for small doses. For doses under 15 units, a 0.3 mL or 0.5 mL syringe provides the best accuracy.

Common Mistakes to Avoid

Even experienced researchers make reconstitution errors. These are among the most common errors encountered during reconstitution.

1. Spraying Water Directly Onto the Powder

Forcing a stream of bac water directly onto the lyophilized cake can cause foaming and denaturation. Always aim for the glass wall and let the liquid run down gently.

2. Shaking the Vial

Vigorous shaking introduces air bubbles and can break peptide bonds. Gentle swirling or slow rolling is all that’s needed. If the powder doesn’t dissolve within a few minutes, let the vial sit in the refrigerator for 30 minutes — most peptides will dissolve on their own.

3. Using the Wrong Volume and Miscalculating Concentration

If you add 2 mL of bac water but calculate your dose as if you added 1 mL, you will administer half the intended amount. Always record the exact volume you added and double-check with the reconstitution calculator.

4. Contaminating the Vial

Failing to swab the stopper, reusing needles, or touching the needle tip with your fingers can introduce bacteria into the vial. Use a fresh alcohol swab and a new needle every time you access the vial.

5. Leaving Reconstituted Peptides at Room Temperature

Peptides degrade rapidly outside refrigeration once reconstituted. Return the vial to the refrigerator immediately after drawing your dose. Never leave a reconstituted vial sitting on a countertop for extended periods.

6. Freezing Reconstituted Peptides

While lyophilized (dry) peptides can be stored in a freezer, reconstituted peptides should generally not be frozen. The freeze-thaw cycle can damage the peptide structure. Keep reconstituted vials refrigerated at 2—8 degrees Celsius.

Storage After Reconstitution

Proper storage is critical for maintaining peptide potency over time. Here are the general guidelines:

Storage Condition	Shelf Life
Reconstituted, refrigerated (2—8 C)	14—28 days (varies by peptide)
Lyophilized, refrigerated	6—12 months
Lyophilized, frozen (-20 C)	12—24+ months

Key storage tips:

• Always store reconstituted peptides in the refrigerator, not the freezer
• Keep vials upright to minimize contact between the solution and the rubber stopper
• Protect vials from direct light, which can accelerate degradation — some researchers wrap vials in aluminum foil
• Record the reconstitution date on each vial and discard solutions older than 28 days
• If the solution becomes cloudy, discolored, or develops particles, discard it immediately

For a deeper look at how temperature, light, and time affect peptide integrity, read our full guide on peptide storage and stability.

Frequently Asked Questions

What is the best water-to-peptide ratio for reconstitution?

There is no single “best” ratio. The amount of bacteriostatic water you add determines the concentration. Common choices are 1 mL or 2 mL per vial. Using 1 mL creates a more concentrated solution (fewer units per dose), and using 2 mL creates a more dilute one (more units per dose). Choose whichever makes your target dose fall within a comfortable range on your syringe — typically between 5 and 50 units.

Can I use sterile water instead of bacteriostatic water?

Yes, but sterile water contains no preservative, so the reconstituted peptide should be used within 24 hours or stored with extreme care. Bacteriostatic water is strongly preferred for multi-dose vials because the 0.9% benzyl alcohol inhibits bacterial growth over the life of the vial.

How do I know if a peptide has gone bad after reconstitution?

Signs of degradation include cloudiness, visible particles or floaters, unusual color changes, or a foul odor. A degraded peptide may also simply lose efficacy over time without visible signs, which is why adhering to storage timelines is important.

How long can I store a reconstituted peptide in the fridge?

Most reconstituted peptides remain stable for 14 to 28 days when refrigerated at 2—8 degrees Celsius. Some more robust peptides may last longer, while others (particularly larger or more complex sequences) may degrade sooner. When in doubt, reconstitute only what you will use within two weeks.

What size syringe should I use to draw my dose?

Use the smallest syringe that accommodates your dose volume. For most peptide protocols, a 0.5 mL (50-unit) insulin syringe provides the best balance of capacity and readability. If your dose is under 15 units, consider a 0.3 mL syringe for maximum precision.

Can I mix two different peptides in the same syringe?

Some researchers do combine compatible peptides in a single injection for convenience. However, stability data on peptide combinations is limited. If you choose to combine peptides, draw each from its own reconstituted vial into the same syringe rather than mixing dry powders together before reconstitution.

I accidentally added more bac water than intended. Is the peptide ruined?

No — don’t panic. The peptide isn’t ruined; the solution is simply more dilute than planned. Recalculate your concentration using the actual volume you added, and adjust your dose volume accordingly. The reconstitution calculator makes this easy.

What is the difference between reconstitution and dilution?

Reconstitution is the initial act of dissolving a lyophilized powder into liquid. Dilution is the process of adding more solvent to an already-reconstituted solution to reduce its concentration. Both are valid techniques, but reconstitution always comes first.

Putting It All Together

Peptide reconstitution is a simple, repeatable process once you understand the fundamentals. To recap:

1. Gather clean supplies: peptide vial, bacteriostatic water, syringes, and alcohol swabs
2. Swab all vial stoppers with alcohol
3. Slowly add your chosen volume of bac water against the glass wall of the peptide vial
4. Gently swirl until fully dissolved — never shake
5. Calculate your concentration: total mcg divided by total mL
6. Use the reconstitution calculator to determine exactly how many syringe units to draw for your target dose
7. Store the vial upright in the refrigerator and use within 28 days

For compound-specific protocols, check out our BPC-157 research guide which includes dosing ranges, reconstitution recommendations, and protocol timelines.

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Need supplies? Shop bacteriostatic water and peptides at Peptide Restore — 5% off with code DKE4PDRM.

Disclaimer: This article is provided for educational and informational purposes only. All peptides referenced are intended for research use only and are not approved for human consumption. Nothing in this article constitutes medical advice. Always comply with applicable laws and regulations in your jurisdiction.