Mixing before calculating
The water volume cannot be changed once it is in the vial. Add 1 ml to a 10 mg vial and a 200 mcg dose is 2 units, which is at the limit of what a barrel can measure. That is a permanent property of that vial now.
Procedure
Decide the water before you open the vial.
Reconstitution is not difficult, but one step has to happen before any of the others. The volume of water you add fixes the concentration permanently, and every dose you draw afterwards depends on it.
- Steps
- 9
- Time
- 5 min
- Needs
- Bac water
- Cost
- Free
The science
What reconstitution actually is
01
A lyophilised peptide is freeze dried: the water has been removed under vacuum, leaving a solid cake or a thin film at the bottom of the vial. Dry, it is far more stable than it would be in solution, which is why it ships that way. Reconstitution is simply adding a measured volume of liquid to put it back into solution so it can be injected.
02
The liquid is normally bacteriostatic water, which is sterile water containing roughly 0.9 percent benzyl alcohol as a preservative. That preservative is the reason a vial can be entered on more than one occasion. Plain sterile water has no preservative, so a vial reconstituted with it is single use in practice, whatever the intention was.
03
The volume you add is a free choice, and it is the only choice that matters. Vial mass divided by water volume is the concentration, and concentration is what converts a dose into a mark on a syringe. Five milligrams in one millilitre and five milligrams in five millilitres contain exactly the same peptide, but a given dose is five times further up the barrel in the second case.
04
Gentleness is the other half of the technique. Peptides are long molecules held in a particular shape, and vigorous shaking applies shear forces and creates an air and liquid interface at the foam boundary, both of which can degrade them. Directing the water at the glass and swirling rather than shaking is not fussiness, it is the reason the instructions say so.
Procedure
Nine steps, in the order they have to happen
The sequence matters more than it looks. Steps one and eight are the two that cannot be done retroactively, and they are the two most often skipped.
- 01
Work out the water volume first
Decide the concentration before you open anything. Vial mass divided by water volume gives mg per ml, and that figure determines every dose you draw afterwards. Choosing it in advance, rather than after the vial is already wet, is what stops you from having to guess later.
- 02
Let a cold vial reach room temperature
If the powder has been refrigerated, leave it out until it is no longer cold to the touch. Injecting a cold solution is uncomfortable, and condensation on a cold vial makes the stopper harder to keep clean.
- 03
Wash your hands and set out a clean surface
Hands first, then lay out the peptide vial, the bacteriostatic water, alcohol swabs and your syringes on a surface you have wiped down. Everything you need should be within reach before anything is unsealed.
- 04
Swab both stoppers and let them dry
Wipe the rubber stopper of the peptide vial and the water vial with a fresh alcohol swab, then let each air dry rather than fanning or blowing on it. The drying time is doing the work, so cutting it short defeats the point.
- 05
Draw the water you calculated
Using a syringe large enough for the whole volume, draw the exact amount of bacteriostatic water you decided on in the first step. Drawing it in one go rather than several partial fills keeps the measurement accurate and limits how often you enter the stopper.
- 06
Run the water down the inside wall of the vial
Angle the needle so the stream lands on the glass wall and flows down, rather than firing directly into the powder cake. Peptides are fragile, and the point of aiming at the wall is to avoid the mechanical stress of a jet hitting the solid.
- 07
Swirl gently, and do not shake
Roll or swirl the vial slowly until the powder has gone into solution. Shaking creates foam and shear forces that can damage the peptide. Dissolution usually takes seconds to a minute or two, and a vial that stays cloudy or leaves visible particles after that is a reason to stop and reconsider the vial rather than to keep agitating it.
- 08
Label the vial with the date and the concentration
Write the reconstitution date and the mg per ml on the vial itself. This is the step people skip and the one that causes the most trouble later, because a solution with no recorded concentration cannot be dosed accurately and a vial with no date cannot be judged against a storage window.
- 09
Store it cold and draw from it with a clean stopper each time
Reconstituted peptide generally goes in the refrigerator rather than the freezer. Swab the stopper before every subsequent draw. Bacteriostatic water contains benzyl alcohol specifically so that a vial can be entered more than once, but that preservative assumes the stopper is cleaned each time, not instead of it.
Common errors
The four that cause the most trouble
Not writing the concentration down
A units figure is meaningless without the concentration behind it. An unlabelled vial a fortnight later is a vial you cannot dose accurately, and no amount of arithmetic recovers a number you never recorded.
Shaking to speed it up
Foam is the visible sign of shear stress at the air and liquid boundary, and that stress is what damages peptides. A slow swirl takes longer and is the reason the instruction exists.
Swabbing once and trusting it
The preservative in bacteriostatic water assumes a clean stopper on every entry, not instead of one. Swab before each draw, and let it dry rather than wiping it off or fanning it.
FAQ
Common questions
How do you reconstitute a peptide step by step?
Decide your water volume first, bring a refrigerated vial to room temperature, wash your hands and wipe both stoppers with alcohol swabs, let them air dry, draw the calculated volume of bacteriostatic water, run it slowly down the inside wall of the peptide vial rather than into the powder, swirl gently until dissolved without shaking, then label the vial with the date and the resulting concentration and refrigerate it.
How much bacteriostatic water should I use?
There is no single right answer, because the volume is a choice about measurement rather than a property of the peptide. More water makes each dose sit further up the syringe where it is easier to read accurately, and less water means the vial holds more doses within a storage window. The practical target is a volume that puts your dose somewhere between roughly 10 and 50 units on a U-100 barrel.
Can I use sterile water instead of bacteriostatic water?
Only for something you will use once. Bacteriostatic water contains benzyl alcohol as a preservative, which is what makes entering the same vial repeatedly over a period of days reasonable. Sterile water has no preservative, so a multiple use vial prepared with it carries a substantially higher contamination risk.
Why should you not shake a peptide vial?
Shaking creates foam and generates shear forces at the air and liquid boundary, and both can damage the structure of a peptide molecule. Swirling or gently rolling the vial dissolves the powder without that stress. Aiming the water stream at the glass wall rather than directly at the powder cake is the same principle applied a step earlier.
How long does a reconstituted peptide last?
A solution is far less stable than dry powder, so the usable window shortens considerably once water is added. The specific window depends on the compound, the storage temperature and the source, which is why labelling the vial with its reconstitution date matters. The vial expiry calculator on this site converts a window into a dose count so you can see whether your dilution will be finished in time.
What if the powder does not fully dissolve?
Give it a minute or two of gentle swirling, since some cakes take longer than others. If the solution stays cloudy, or visible particles remain after that, the answer is to stop rather than to agitate harder. Persistent undissolved material is information about the vial, and continuing to shake it addresses the symptom rather than the cause.
Do I need to calculate anything before mixing?
Yes, and it is the one step that cannot be done afterwards. The water volume sets the concentration permanently for that vial, so if you add liquid before deciding what dose you want to be able to draw, you may end up with a concentration that puts your dose below two units on the barrel, where it cannot be measured accurately. Working out the volume first takes a moment and cannot be undone later.
VialClock
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