Dilution math is the single most common question we receive. We break it down from first principles — no assumptions, no guesswork.
Reconstitution — the act of dissolving a lyophilized (freeze-dried) peptide into a usable solution — is the single most common point of confusion for new researchers, and the single most common source of dosage error. The math is not complicated. It is, however, unforgiving when done by feel.
This is a first-principles walkthrough. We are deliberately avoiding shortcuts; the goal is for the math to make sense, not for you to memorize a formula.
A vial of lyophilized peptide arrives with a fixed mass of peptide inside — nothing more. The label might say 10mg, but until you add liquid, that 10mg is a thin pale powder pressed against the bottom of the vial. There is no concentration yet because there is no solution.
Concentration is created the moment you add bacteriostatic water. Choose how much water you add, and you choose the concentration.
One relationship governs everything that follows:
concentration = total peptide mass ÷ volume of solvent added
If you add 2 mL of bacteriostatic water to a 10 mg vial, you have a solution that contains 10 mg in 2 mL — or 5 mg per mL. That is your concentration.
Everything else — what to draw into the syringe, how much one "unit" delivers, how long the vial lasts — flows from this single number.
Standard U‑100 insulin syringes are calibrated for insulin and not for peptides, but the unit markings are honest in volume terms: 100 units = 1 mL, so 10 units = 0.1 mL.
If your concentration is 5 mg/mL, then:
The volume the syringe measures is the same regardless of what is in the vial. The dose changes only because the concentration changes.
How much water you add is a choice, not a rule. More water gives lower concentration and more units per dose — useful for very small target doses where you want larger, easier-to-measure volumes. Less water gives higher concentration and fewer units per dose — useful when total injection volume matters.
A common starting choice for a 10 mg vial is 2 mL of bacteriostatic water, yielding 5 mg/mL. For a 5 mg vial, 1 mL of water yields the same 5 mg/mL. Round-number concentrations make subsequent math easier.
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol — an antimicrobial preservative that prevents bacterial growth in a multi-use vial. Sterile water without preservative is acceptable for a single-use scenario but invites contamination as soon as the seal is broken a second time. Distilled water is not sterile and is never appropriate for reconstitution.
Angle the syringe needle against the inside wall of the peptide vial and let the water trickle slowly down the side. Do not aim directly at the lyophilized powder — that can damage the peptide structure through shear. Once all the water is in, swirl the vial gently between your fingers. Do not shake. Most peptides dissolve within seconds; some take a minute or two of patient swirling. The solution should be clear and free of visible particles.
Once reconstituted, the vial belongs in a refrigerator (2–8°C), away from light. Most peptides retain potency for 28 days under refrigeration. Some — particularly the more fragile sequences — degrade faster. When in doubt, draw and use sooner rather than later.
You have a vial of GHK-Cu 50mg. You add 2.5 mL of bacteriostatic water.
The math is the same for every peptide. Mass divided by volume gives concentration. Target dose divided by concentration gives volume. Volume translated to syringe units gives the practical answer at the bench.
If a number does not feel right, do not proceed. Most reconstitution errors are off by a factor of 10 — an entire decimal place — and they are caught immediately if you stop and think. Write the equation out. Check the units. The arithmetic is simple; the discipline is in slowing down for it.
Our reconstitution reference includes worked examples for the most common compounds in the catalog. The interactive calculator below walks through the same math for any peptide and water volume you specify.
This article is provided for informational and educational purposes only. Lumira Labs products are sold strictly for laboratory research use and are not for human consumption, medical use, or veterinary application. The compounds discussed are not approved by Health Canada or the FDA for any therapeutic indication. Nothing in this article should be construed as medical advice.