How does the amount of water change the concentration?

The peptide mass is fixed; only the volume changes. Concentration equals peptide milligrams divided by milliliters of water. Adding more water lowers the concentration (mg/mL) and increases the volume drawn per unit; adding less water raises the concentration. The total number of doses per vial does not change with water volume - only the volume of each draw.

How do I calculate syringe units for a target dose?

Divide the target amount by the concentration to get the volume in milliliters, then convert to insulin-syringe units (1 mL = 100 units on a U-100 syringe). Our free reconstitution and dosage calculator does this automatically once you enter vial size, water volume, and target amount.

How should a reconstituted peptide be stored?

Reconstituted vials are refrigerated at roughly 2-8 degrees Celsius and, as a general research guideline, used within about 28 days of mixing. Lyophilized (unmixed) powder is far more stable and is kept frozen or refrigerated and protected from light.

Lab How-To · Research Use Only

How to reconstitute a peptide

Q: What water do you use to reconstitute a peptide?

Bacteriostatic water is the standard reconstitution fluid for multi-use research vials because the added benzyl alcohol inhibits microbial growth. Sterile or plain water is sometimes used for single-use preparations. Both are added slowly against the inside wall of the vial.

Research peptides ship as a lyophilized (freeze-dried) powder. Before use in the lab they are reconstituted - dissolved in a measured volume of bacteriostatic water. The volume you add sets the concentration, and the concentration is what turns a target amount into a number of syringe units. Here's how the process works, step by step.

Research use only. This guide describes standard laboratory handling of research materials. It is educational reference, not medical advice, and does not describe human dosing. All products are sold strictly for laboratory research and are not for human consumption.

What you need

The lyophilized peptide vial - the freeze-dried powder, usually a small pellet or film at the bottom of the vial.
Bacteriostatic water - sterile water with 0.9% benzyl alcohol added to inhibit microbial growth in multi-use vials. We stock bacteriostatic water alongside the peptides.
A sterile syringe to measure and transfer the water, plus an alcohol wipe for the vial stoppers.

Step by step

Let both vials reach room temperature. Cold glass and cold water make mixing slower and can stress the peptide. Wipe both rubber stoppers with an alcohol swab.
Draw your measured water volume. Decide how many milliliters of bacteriostatic water to add - this single choice sets your concentration. Draw that exact volume into the syringe.
Add the water slowly, down the vial wall. Insert the needle and let the water run gently against the inside glass rather than blasting directly onto the powder. Peptides are delicate; a slow stream protects them.
Swirl - do not shake. Gently roll or swirl the vial until the powder fully dissolves and the solution is clear. Shaking creates foam and mechanical stress. If it doesn't dissolve in seconds, let it sit a minute and swirl again.
Label and refrigerate. Note the date and concentration on the vial, then store it in the refrigerator. As a general research guideline, reconstituted vials are used within about 28 days.

How water volume sets concentration

The key idea: the peptide mass in the vial is fixed - only the water volume changes. Concentration is simply mass divided by volume:

Concentration = peptide (mg) ÷ water (mL)

A 10 mg vial reconstituted with 1 mL of water gives a concentration of 10 mg/mL. The same 10 mg vial with 2 mL of water gives 5 mg/mL.

Adding more water doesn't add or remove peptide - it just spreads the same amount across a larger volume, so each measured draw is larger and easier to read on the syringe. The total number of doses in the vial stays the same either way.

Turning concentration into syringe units

Once you know the concentration, a target amount converts to a volume, and that volume converts to units on an insulin syringe (1 mL = 100 units on a U-100 syringe):

Volume (mL) = target amount (mg) ÷ concentration (mg/mL)

At 5 mg/mL, a 0.5 mg target draw is 0.5 ÷ 5 = 0.1 mL, which is 10 units on a U-100 syringe.

You don't have to do this by hand. Our calculator takes the vial size, water volume, and target amount and returns the exact syringe units, concentration, and doses per vial instantly.

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Free peptide reconstitution & dosage calculator

Enter vial size, water volume, and target amount - get exact syringe units in one screen.

Storage & stability basics

Lyophilized powder is the most stable form - keep it frozen or refrigerated and away from light until you reconstitute.
Reconstituted solution is refrigerated at roughly 2–8 °C and, as a general guideline, used within about 28 days.
Avoid repeated freeze–thaw cycles of the reconstituted solution, direct heat, and vigorous shaking - all of which can degrade peptides.

Frequently asked questions

What water do you use to reconstitute a peptide?

Bacteriostatic water is the standard for multi-use research vials because the added benzyl alcohol inhibits microbial growth. Sterile or plain water is sometimes used for single-use preparations. Either way, add it slowly against the inside wall of the vial. We carry bacteriostatic water in the catalog.

Does adding more water reduce the total doses in the vial?

No. The peptide mass is fixed, so the number of doses stays the same. More water only lowers the concentration (mg/mL) and makes each individual draw a larger, easier-to-measure volume.

How do I calculate syringe units for a target amount?

Divide the target amount by the concentration to get milliliters, then multiply by 100 for U-100 syringe units. The reconstitution & dosage calculator does it automatically.

How long does a reconstituted peptide last?

Refrigerated at about 2–8 °C, reconstituted vials are generally used within about 28 days as a research guideline. Unmixed lyophilized powder lasts far longer when kept frozen and protected from light.

Related guides

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Research Use Only. All products are sold strictly for laboratory and research purposes and are not for human consumption, medical, veterinary, or diagnostic use. Your Peptide Partner is not a compounding pharmacy under Section 503A, nor an outsourcing facility under Section 503B, of the Federal Food, Drug, and Cosmetic Act. This page is educational reference only - it is not medical advice or dosing guidance. By ordering you confirm you are a qualified purchaser and agree to our Terms & Conditions; all orders are subject to review and acceptance. See our Research Compliance policy.