Read this first
This is plain-language harm-reduction information, not medical advice. Peptides discussed here are research compounds; most are not approved for human use. People will use them either way — we would rather they have the facts.
To reconstitute a peptide, you add a measured amount of sterile liquid, usually bacteriostatic water, to the freeze-dried powder in the vial, let it dissolve by gentle swirling, then label the vial with the concentration and date. The maths is the part people get wrong, so most of this guide is about getting that right.
A quick framing note: most of the compounds covered on this site are research chemicals or unlicensed medicines, and the evidence for many of them is animal-only or anecdotal. This guide is harm-reduction information about technique, not medical advice and not a recommendation to use anything.
What reconstitution actually means
Most peptides are shipped as lyophilised (freeze-dried) powder because they are far more stable dry than in liquid. Reconstituting just means turning that powder back into a solution you can measure. Nothing chemical is meant to happen. You are dissolving, not reacting.
Once the powder is wet, the clock starts. The peptide begins to degrade slowly, and the liquid becomes something bacteria can grow in. That is why the choice of water and your technique both matter.
What you need
- The vial of peptide (check the amount in mg on the label)
- A suitable diluent, most often bacteriostatic water. A few peptides are dissolved in dilute acetic acid water instead
- A new sterile syringe for mixing (a 3 ml syringe is easier for adding water than an insulin syringe)
- A new sterile insulin syringe for measuring doses, if you are going to inject
- Alcohol swabs (isopropyl, 70%)
- A marker or label, and a clean, flat surface
Step-by-step
- Prepare the space. Wash your hands properly, wipe the surface down, and lay everything out before you start. Do not do this over a dirty desk with the cat on it.
- Check the vial. The powder should be a white or off-white fluffy cake or thin puck, with an intact cap. If it is discoloured, melted-looking or the seal is damaged, stop. See the safer use page for more on what to check.
- Swab the stoppers. Wipe the rubber top of the peptide vial and of the water vial with an alcohol swab and let it air-dry for a few seconds.
- Draw up the water. Pull the amount of diluent you have decided on (see the maths below) into the mixing syringe. Remove any big air bubbles.
- Add it slowly. Push the needle through the stopper and angle it so the water runs down the inside wall of the vial. Do not blast it onto the powder, as the force can damage fragile peptide chains.
- Swirl, do not shake. Withdraw the needle and gently roll or swirl the vial. Most peptides dissolve in seconds to a few minutes. Shaking creates foam and can degrade the peptide. If it is stubborn, leave it in the fridge for a while and swirl again.
- Inspect it. The solution should be clear and colourless, perhaps very faintly straw-coloured for some peptides. Cloudiness, flecks or strings that do not clear are a reason not to use it.
- Label it. Write the peptide name, the total mg, the volume of water you added, the resulting concentration and the date. Do this immediately, not later.
- Refrigerate. Put it in the fridge, upright, and away from light.
The maths: a worked example
The key idea is that a standard insulin syringe holds 1 ml and is marked in 100 units, so 1 unit = 0.01 ml. Everything follows from the concentration you create.
Say you have a 5 mg vial and add 2 ml of water.
- 5 mg is 5,000 mcg. Divided by 2 ml gives 2,500 mcg per ml.
- A 1 ml syringe has 100 units per ml, so 2,500 mcg / 100 = 25 mcg per unit.
- If you wanted a 250 mcg dose, that is 250 / 25 = 10 units.
Now the same 5 mg vial with 1 ml of water instead: 5,000 mcg per ml, so 50 mcg per unit, and 250 mcg is 5 units. Less water means a stronger solution and a smaller volume per dose. More water means a weaker solution and a larger, easier-to-read volume.
Write the maths down and check it twice, ideally using a different route (for example, work out the dose in ml, then convert to units). A decimal-point slip means a tenfold error. There is more on this in our dosing maths guide.
How much water should you add?
There is no single correct answer. Two things guide the choice: the dose you plan to measure and how readable the syringe will be. Small doses in tiny volumes are hard to measure accurately, so many people add more water to make the numbers friendlier, such as 2 ml for a 5 mg vial. Just remember you cannot un-dilute, and a bigger volume does not change how much peptide is in the vial.
Your peptide's page may suggest typical volumes, for example BPC-157 and TB-500 are commonly shown with 2 ml examples. Treat these as arithmetic illustrations, not instructions.
Sterile technique basics
- Use a new sterile needle and syringe every time. Never reuse them, and never share.
- Swab every stopper before every puncture, even if you swabbed it yesterday.
- Do not touch the needle or the stopper surface with your fingers.
- Do not use tap water, boiled water or "distilled" water from a supermarket. These are not sterile.
- Discard a vial that looks wrong, has been dropped, or has been punctured many times with a dirty technique.
Which water: bacteriostatic, sterile or acetic acid?
Bacteriostatic water contains 0.9% benzyl alcohol, which limits bacterial growth and lets a vial be punctured several times. Plain sterile water has no preservative, so it is generally treated as single-use. A few hard-to-dissolve peptides, such as IGF-1 LR3, are typically dissolved in dilute acetic acid. Our comparison, BAC water vs sterile water vs acetic acid, covers this in detail.
How long does it last once mixed?
Honest answer: it depends on the peptide, and much of the published guidance is vendor or community convention rather than formal stability testing. On this site, the pages for common peptides such as BPC-157 and CJC-1295 give figures of roughly three to four weeks refrigerated, and some others up to six to eight weeks. If it is cloudy, smells odd or has been left out warm, bin it regardless of the date. See how to store peptides for more.
Common mistakes
- Shaking the vial hard and creating foam
- Forgetting to write down how much water went in, then guessing later
- Mixing up mg and mcg (1 mg = 1,000 mcg)
- Using a vial of "water for injection" that has been open for weeks
- Adding a blend's water volume as if it were a single-peptide vial. A blend such as CJC-1295 with ipamorelin has two compounds, so you need to know the amount of each
Bottom line
Reconstitution is simple: clean surfaces, clean stoppers, slow gentle mixing, a clear solution and a proper label. The real risk is arithmetic and hygiene, not chemistry. If the numbers do not feel obvious to you, slow down and recheck before drawing anything up. These are mostly unlicensed research compounds, so the responsibility for checking is yours.
Common questions
Can I reconstitute a peptide with normal tap water?
No. Tap water is not sterile and can contain bacteria and impurities. Sterile diluents such as bacteriostatic water are used because the solution is kept for days or weeks.
How many units is 250 mcg of a peptide?
It depends on the concentration. In a 5 mg vial mixed with 2 ml of water, there are 25 mcg per unit on a 1 ml insulin syringe, so 250 mcg is 10 units.
Why should I swirl instead of shake a peptide vial?
Shaking can create foam and put mechanical stress on the peptide chains, which may degrade them. Gentle swirling dissolves the powder just as well, only slower.
What should reconstituted peptide look like?
Typically clear and colourless, sometimes a very faint straw tint. Cloudiness, floating particles or discolouration are reasons not to use it.