Read this first
This guide is written for qualified researchers handling materials in a laboratory
setting. It is general reference information about laboratory technique and dilution
arithmetic. It is not instructions for human or veterinary use, and nothing here
recommends an amount to use.
Start here
Pick what is in front of you and it tells you exactly how much
bacteriostatic water to add. We aim for a round ratio so the sums stay easy.
What "reconstitution" actually means
Your vial contains a dried powder. The powder was frozen and the water pulled out of it
(freeze-drying, or "lyophilisation"), because dry powder keeps far longer than liquid.
Reconstitution is simply the opposite step: you add a measured amount of liquid so the
powder dissolves again and becomes a solution you can measure out accurately.
The liquid used is bacteriostatic water — sterile water containing
0.9% benzyl alcohol, which stops bacteria from growing in the vial after you have opened it.
Plain sterile water has no preservative, so a vial mixed with it does not keep.
The one idea that makes everything else make sense
Adding water does not change how much peptide you have — a 10 mg vial holds
10 mg whether you add 1 mL or 5 mL. What changes is how
concentrated it is, and therefore how much liquid you draw to get a given
amount. More water means a weaker solution and a bigger, easier-to-measure volume.
What you need
- Your vial of lyophilised powder
- Bacteriostatic water
- A sterile syringe — the ones we ship are 0.5 mL U-100 insulin
syringes with a fixed 30G needle. A 0.5 mL barrel is graduated
0–50 units, so one completely full syringe is half a millilitre.
Nearly every volume on this page is larger than that, so you will be filling the
syringe more than once — the calculator tells you how many times.
- Alcohol wipes
- A sharps container for used needles
- A clean, draught-free surface with good light
Step by step
1
Let the vial come to room temperature
Take it out of the fridge and give it about 20 minutes. Adding liquid to
ice-cold powder makes it dissolve slowly and unevenly.
2
Work out your volume before you touch anything
Decide how much bacteriostatic water you are going to add and write it down.
Use the calculator below. Changing your mind halfway is how mistakes happen.
3
Clean both stoppers
Wipe the rubber top of the peptide vial and of the bacteriostatic water vial with
a fresh alcohol wipe, and let them air-dry. Do not remove the metal ring — you push
the needle straight through the rubber centre.
4
Draw the water
Pull your chosen volume of bacteriostatic water into the syringe. Hold it upright,
tap the barrel so any air bubbles rise, and push them out before you continue.
5
Let it run down the glass — do not blast the powder
Angle the needle so the water runs down the inside wall of the vial. Push
slowly. Firing a jet straight onto the powder can damage the peptide. This is the single
most common mistake.
6
Wait. Do not shake.
Set the vial down and let it dissolve on its own; this usually takes a few minutes.
If a little powder is clinging on, roll the vial gently between your fingers or swirl it.
Never shake it — shaking foams the solution and breaks the peptide apart.
7
Check it, label it, refrigerate it
The solution should be clear and colourless with nothing floating in it. Write the
date and the concentration on the vial — in three weeks you will not remember —
and put it in the fridge.
If it does not look right, stop. Cloudiness, visible particles, colour, or
powder that will not dissolve after 15 minutes all mean something is wrong. Do not use it.
Mixing calculator
Work out your concentration
Enter the three numbers and it does the arithmetic for you.
It converts units — it does not recommend any amount.
Concentration of the mixed vial–
Draw this much on a U-100 insulin syringe–
Which is this volume of liquid–
Draws of that size in the vial–
How the calculator works
There is no magic in it — it is two divisions, and it is worth understanding them so
you can sanity-check the answer yourself.
| Concentration |
peptide (mg) ÷ water (mL)
10 mg ÷ 2 mL = 5 mg per mL |
|---|
| Volume per draw |
amount you want ÷ concentration
0.25 mg ÷ 5 mg/mL = 0.05 mL |
|---|
| Syringe units |
volume (mL) × 100
0.05 mL = 5 units |
|---|
Why "units" and not mL
An insulin syringe is marked in units, not millilitres, and 100 units = 1 mL.
So 10 units is 0.1 mL and 50 units is half a millilitre. Mixing these two
scales up is the classic ten-fold error, which is exactly why the calculator prints both.
The syringes we ship are the U-100 type in the 0.5 mL size, so their scale runs
0–50 units and a full barrel is 0.5 mL. The unit numbers above are
the same on any U-100 syringe; only the length of the scale differs. Watch for this when a
volume is bigger than one barrel: "add 1.0 mL" means two full syringes, not one.
If you use a syringe from elsewhere, check that it says U-100 or 100 I.E. before you rely
on the unit figure — and check its capacity, because U-100 syringes are sold in
0.3, 0.5 and 1 mL barrels that all use the same unit scale.
Notice what happens if you add 5 mL to that same 10 mg vial instead of 2 mL:
the concentration drops to 2 mg/mL and the same 250 mcg becomes 12.5 units
instead of 5. Same peptide, same amount — just easier to measure. If your figure comes
out below about 5 units, mixing with more water will make it far easier to draw accurately.
Storage and shelf life
| Unopened dry powder | Refrigerated, in the dark. Check the label for the compound's own figure. |
|---|
| After reconstitution | Refrigerate at 2–8 °C. Keep it upright, away from light. |
|---|
| Do not freeze it | Freezing and thawing a mixed vial degrades most peptides. |
|---|
| How long it keeps | Depends on the compound — follow the figure for the specific material rather than a general rule. |
|---|
Common mistakes
- Shaking the vial. Swirl or roll it instead.
- Spraying water onto the powder. Run it down the wall of the vial.
- Confusing mg and mcg. 1 mg = 1000 mcg.
- Confusing units and mL. 100 units = 1 mL on a U-100 syringe.
- Using plain sterile water. No preservative, so the vial will not keep.
- Not labelling the vial. Write the date and concentration on it.
- Re-using needles. One use, then the sharps container.
Still not sure?
Email [email protected] with your vial size and what
you are trying to work out, and we will walk through the arithmetic with you.
Always follow your institution's safety protocols. All products sold by Pepsup are supplied
for laboratory research use only and are not for human or veterinary consumption.