Peptide Essentials

Peptide Reconstitution Chart: mg/mL by Vial Size and Water

Underground Biohacking|8 min readPublished Aug 5, 2026|Updated Oct 30, 2026

Peptide reconstitution chart of mcg per mL by vial size and water volume

What Does a Peptide Reconstitution Chart Tell You?

A peptide reconstitution chart answers one question. How strong is the vial once the water goes in? That strength is written in micrograms per millilitre (mcg/mL). A microgram is one thousandth of a milligram. Every syringe reading afterwards follows from this one figure.

Two quantities decide it. One is the powder weight printed on the label, in milligrams (mg). The other is the volume of water added, in millilitres (mL). One divided by the other is the whole of the peptide reconstitution sum. The sum gives the strength on paper. It assumes the label weight is right and that all the powder dissolves.

How Do You Work Out Peptide Reconstitution Concentration?

The sum has two steps. Milligrams times 1,000 gives micrograms. Micrograms divided by millilitres of water gives the strength in mcg/mL.

A second sum turns a dose into a syringe reading. The dose in mcg divided by the strength, times 100, gives the reading. The answer is in units on a U-100 insulin syringe. U-100 means 100 units per mL, the insulin strength a US prescribing sheet pairs with that syringe Lilly, Humulin R, 2018. So on that syringe, 100 units fill 1 mL.

Peptide Reconstitution Chart: the Formula Behind Each Figure

Figure	Unit	How it is found
Powder in the vial	mg	Printed on the vial label
Water added	mL	The volume put into the vial
Strength	mcg/mL	mg × 1,000 ÷ mL of water
Syringe reading	Units on a U-100 syringe	Dose in mcg ÷ strength × 100
Water for a chosen reading	mL	mg × 10 × units ÷ dose in mcg
Twice the water, same powder	mcg/mL	Strength halves, so the same dose needs twice the units

No row lists a vial size or a water volume. Each is a formula, so it suits any combination. Twice the water gives half the strength, every time. This is division, never a curve. The peptide reconstitution calculator works out the strength and the syringe units with these formulas.

How Does Water Volume Change Peptide Reconstitution Strength?

More water makes a weaker solution. The same dose then takes more liquid and a higher syringe reading. Less water makes a stronger solution, and the same dose fills fewer units.

The reverse sum is short. Volume in mL equals vial weight in mg, times 10, times the wanted units, divided by the dose in mcg. Picking a different volume leaves the powder untouched. Only the liquid per dose moves. Our companion piece on converting mcg into syringe units covers what U-100 means and the mcg to units formula.

Does Peptide Reconstitution Change for Retatrutide or Tirzepatide?

The arithmetic does not change. It is the same for any lyophilised powder, meaning a freeze-dried one, that fully dissolves.

Retatrutide, tirzepatide, tesamorelin, GHK-Cu and AOD-9604 powders all follow the same formula. What separates them is the dose and how often it is given. Neither comes from the mixing sum.

Some forms are never mixed at all. Zepbound, a tirzepatide brand, ships as a ready-made sterile solution in pens and vials, according to Lilly's prescribing information Lilly, Zepbound, 2026. Retatrutide is a drug still under study in phase 3 trials, the large, late stage of testing in people. Eli Lilly runs them ClinicalTrials.gov NCT05929066.

Egrifta WR is a licensed tesamorelin powder. Its label from the US Food and Drug Administration (FDA) names the diluent, the volume and the resulting strength. It says to swirl the vial, and not to shake it Theratechnologies, Egrifta WR, 2025. Those steps belong to that product alone. Our walkthrough on how to reconstitute peptides covers the bench routine, and how to inject peptides picks up after the draw.

What Is Bacteriostatic Water for Peptide Reconstitution?

Bacteriostatic water is sterile water with benzyl alcohol added as a preservative. Hospira lists 0.9% or 1.1% of it. It comes in a multiple-dose container, and repeated withdrawals may be made from it Hospira, bacteriostatic water.

Hospira warns it is not for use in newborns. Some drugs may also clash with benzyl alcohol, the sheet adds. Hospira's plain sterile water has no preservative and comes only in single-dose containers. Leftover liquid is to be discarded, its sheet says Hospira, sterile water.

What Do Labels Say About Storage After Peptide Reconstitution?

We found no primary source that sets a usable window for a mixed research peptide. One prescribing sheet sets rules for its own product. Egrifta WR says to throw away unused mixed solution 7 days after mixing, and not to freeze it. It also says to throw away its bacteriostatic water 28 days after first use Theratechnologies, Egrifta WR, 2025. Those limits cover Egrifta WR only.

What Can a Peptide Reconstitution Chart Not Tell You?

A chart only gives the strength on paper. It cannot check the label weight, and it does not give a dose. Our article on why most peptide dosing advice gets it wrong covers the mixing maths behind a dose.

Everything here assumes the milligram amount printed on the vial is true. An underfilled vial makes every result on this page wrong. Our sources page sets out how we grade vendors.

References

Vasireddi et al. 2025, "Emerging Use of BPC-157 in Orthopaedic Sports Medicine: A Systematic Review," HSS J. PubMed
Seiwerth et al. 2021, "Stable Gastric Pentadecapeptide BPC 157 and Wound Healing," Front Pharmacol. PubMed
Goldstein et al. 2011, "Thymosin β4: a multi-functional regenerative peptide," Expert Opin Biol Ther. PubMed
Pickart et al. 2018, "Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data," Int J Mol Sci. PubMed
Eli Lilly, HUMULIN R prescribing information, revised May 2018. Drugs@FDA
Eli Lilly, ZEPBOUND (tirzepatide) prescribing information, revised February 2026. Drugs@FDA
Theratechnologies, EGRIFTA WR (tesamorelin) prescribing information, revised March 2025. Drugs@FDA
Hospira, Bacteriostatic Water for Injection, USP. Pfizer Labeling
Hospira, Sterile Water for Injection, USP. Pfizer Labeling
Eli Lilly, TRIUMPH-1, a retatrutide phase 3 study. NCT05929066

This content is for educational purposes only. These compounds are intended for research use. Nothing here is medical advice. A qualified clinician can advise on any health decision.

Where to buy research peptides

Our sources page explains how we choose which suppliers we list. Before you buy anything, ask the seller for a recent certificate of analysis (COA) from an independent lab, and check that its batch number matches your vial. We may earn a commission from links on that page.

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Frequently Asked Questions

Does the type of peptide change the reconstitution formula?

No. The formula is plain arithmetic. The mg on the label times 1,000, divided by the mL of water, gives the mcg per mL. It is the same for BPC-157, TB-500, GHK-Cu or any peptide powder that fully dissolves. Peptides differ in dose and in how often each is given. The formula sets neither.

What is bacteriostatic water and why not use sterile water?

Bacteriostatic water is sterile water with a preservative added, called benzyl alcohol. Hospira's label gives 0.9% or 1.1%. It comes in a multiple-dose container, so it can be drawn from more than once. Hospira's plain sterile water has no preservative. It comes only in single-dose containers. Its label says to throw away the unused portion. The bacteriostatic label also says it is not for use in newborns.

How long does a reconstituted peptide vial stay usable?

We found no primary source that sets a usable window for a mixed research peptide. One drug label sets a window for its own product. Egrifta WR, a tesamorelin powder, says to throw away unused mixed solution 7 days after mixing. That figure applies to Egrifta WR only. It is not a rule for other peptides.

Can I use a different water volume than a chart recommends?

The formula works with any water volume. More water gives a weaker solution, so the same dose reads as more units. Less water gives a stronger solution, so the same dose reads as fewer units. A licensed product's label can set one volume for that product, as the Egrifta WR label does.

Why do my units not match a chart I found elsewhere?

Three inputs set every figure. They are the powder weight printed on the vial, the water volume added, and the syringe scale. This page uses U-100, which means 100 units per mL. A chart built on a different vial size, water volume or syringe scale gives different units. A change in any one of the three changes every figure after it.

Does temperature affect the concentration once reconstituted?

The formula has no term for temperature. Strength is the powder's mass divided by the water's volume. Cooling or warming a vial adds no powder and removes no water. Labels give storage rules for other reasons. The Egrifta WR label, for one, says not to freeze the mixed solution.