How to Reconstitute Peptides
Turn freeze-dried powder into a usable solution in two minutes, step by step.
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Getting started
How Much Bacteriostatic Water to Use
There's no single "correct" amount — the water you add just sets the concentration. Here's the one formula you need, worked examples, and how to read the result on a syringe.
Reconstitution is just dilution. The peptide amount in the vial is fixed; the water you add decides how concentrated the final solution is. This guide shows the one formula you need, worked examples for common vial sizes, and how to read the result on an insulin syringe.
Research use only. This is an educational explanation of
dilution and measurement math for laboratory research materials. It is not medical advice
and does not describe or recommend human use.
The only formula you need
Concentration (mg/mL) = peptide (mg) ÷ BAC water added (mL)
That's the whole thing. Add less water → more concentrated. Add more water → more dilute. The amount of actual peptide never changes — you're only choosing how it's spread out.
Worked examples
Say you have a 10 mg vial. Here's what different water volumes give you:
| BAC water added | Concentration | Per 0.1 mL (10 units) |
|---|---|---|
| 1 mL | 10 mg/mL | 1.0 mg |
| 2 mL | 5 mg/mL | 0.5 mg |
| 3 mL | 3.33 mg/mL | 0.33 mg |
| 5 mL | 2 mg/mL | 0.2 mg |
And for other common vial sizes, reconstituted with a standard 2 mL:
| Vial size | + 2 mL BAC water | Per 0.1 mL (10 units) |
|---|---|---|
| 5 mg | 2.5 mg/mL | 0.25 mg |
| 10 mg | 5 mg/mL | 0.5 mg |
| 15 mg | 7.5 mg/mL | 0.75 mg |
| 30 mg | 15 mg/mL | 1.5 mg |
Reading it on an insulin syringe
Insulin syringes are marked in units, not millilitres, which trips a lot of people up. On a standard U-100 syringe:
100 units = 1 mL · 50 units = 0.5 mL · 10 units = 0.1 mL
So units are just a finer ruler for volume. With a 10 mg vial in 2 mL (5 mg/mL):
- 20 units = 0.2 mL = 1.0 mg
- 10 units = 0.1 mL = 0.5 mg
- 5 units = 0.05 mL = 0.25 mg
So how much should I actually add?
A practical rule of thumb: 1–2 mL per vial is the common range.
- More water (2–3 mL) → lower concentration → you measure a larger volume, easier to read accurately.
- Less water (1 mL) → higher concentration → you measure a smaller volume.
There's no wrong answer as long as you write the concentration on the vial. New to the mixing step? Start with How to Reconstitute Peptides.
Where to buy
Need bacteriostatic water & tested compounds?
We recommend Vital Chems for clean, research-grade supplies.
- Third-party HPLC tested — COA on every order
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- US-based, fast and responsive support
Frequently asked questions
How much bacteriostatic water should I add to a vial?
It depends on the concentration you want. Use concentration = mg ÷ mL. A common starting point is 1–2 mL per vial — any volume works as long as you track the resulting concentration.
Does adding more water make the peptide weaker?
No. The amount of peptide in the vial is fixed. More water just spreads that same amount across a larger volume, lowering the concentration (mg/mL) — it doesn't change how much peptide is present.
What is a "unit" on an insulin syringe?
On a standard U-100 insulin syringe, 100 units = 1 mL. So 10 units = 0.1 mL and 50 units = 0.5 mL. Units are just a finer way of measuring volume.
Can I change the concentration after I've already mixed it?
You can add more bacteriostatic water to dilute it further (recalculate afterward), but you can't make it more concentrated once mixed. Decide your volume up front.