Peptide Guides
Important
The peptides described on this site are not approved medicines. They hold no licence from the MHRA in the United Kingdom, the EMA in Europe, or the FDA in the United States. This guide covers laboratory handling and concentration calculation only. It is not medical advice, contains no guidance on administration, and nothing within it constitutes a recommendation to use any compound. Products supplied through this site are intended for laboratory research use only.
Quick answer
- Research peptides arrive as freeze-dried powder labelled by weight, not as a ready-made liquid.
- Reconstitution means adding a measured volume of liquid to make a solution of known strength.
- The arithmetic is amount of peptide divided by volume of liquid: a 10mg vial with 5ml added gives 2mg/ml.
- Sealed powder is stable for a long time; the mixed solution is fragile and needs refrigeration.
Why peptides are supplied as freeze-dried powder
Reconstituting a peptide means dissolving the dry powder in a measured amount of liquid, producing a solution whose strength is known exactly.
The powder is dry because peptides are supplied lyophilised, which means freeze-dried. The material is frozen and the water is removed under vacuum, leaving a dry cake or powder in the vial.
The water is removed because peptides dissolved in liquid break down quickly. Water lets the chemical reactions that pull peptides apart get going, and it lets germs grow. Removing it slows both almost to a stop. A sealed vial of dry powder, kept cold and dark, stays stable for a long time. The same peptide in liquid does not.
This is why vials are labelled by weight. A vial labelled 10mg contains 10mg of peptide powder and no liquid. The liquid is added later, and how much is added decides the strength of the solution. Our introduction to peptides covers why small peptides survive freeze-drying so well.
What is needed to reconstitute a peptide
Four items are needed.
The peptide vial. Sealed, containing a stated weight of freeze-dried powder, for example 5mg or 10mg.
A diluent. The liquid the powder will be dissolved in, usually bacteriostatic water. The next section covers the choice.
A syringe with fine markings. Used for measuring the diluent accurately, which is the step the whole calculation depends on. Small graduations give a more reliable measurement than coarse ones.
Alcohol swabs. For wiping the vial stoppers before anything passes through them.
Bacteriostatic water vs sterile water
Two liquids are used to dissolve the powder (“diluent” is the technical word for them), and they are not interchangeable.
Sterile water is water that has been sterilised and contains nothing else. It is germ-free while sealed, but once the vial is opened, nothing stops germs getting in and growing.
Bacteriostatic water is sterile water with a small amount of preservative added (0.9 per cent benzyl alcohol), which stops bacteria growing. A vial of it can be used more than once, over days or weeks, without germs taking hold. It is the standard choice when a solution will be used more than once.
This is why the choice matters. A solution made with sterile water has a much shorter working life, because nothing is holding germs back between uses.
Benzyl alcohol is not just a passenger. It becomes part of the solution, and some peptides break down faster with it than in plain water. Where the specification for a compound names a particular liquid, follow it.
How to calculate peptide concentration
Concentration means how much peptide is dissolved in each millilitre of liquid. The arithmetic is the amount of peptide in the vial divided by the volume of liquid added.
| Vial mass | Diluent added | Resulting concentration |
|---|---|---|
| 5mg | 2ml | 2.5mg/ml |
| 5mg | 5ml | 1mg/ml |
| 10mg | 5ml | 2mg/ml |
| 10mg | 10ml | 1mg/ml |
Adding more liquid does not change how much peptide is present. A 10mg vial contains 10mg whether it is reconstituted with 2ml or 10ml. What changes is how concentrated the resulting solution is, and therefore how much liquid contains a given amount of peptide.
Concentration is often expressed in micrograms per millilitre for convenience, since research quantities are frequently small. There are 1,000 micrograms in a milligram, so 2mg/ml is the same as 2,000mcg/ml.
The powder takes up almost no space, so the volume of liquid you add is effectively the final volume. And accuracy depends entirely on measuring the diluent accurately, since the vial mass is fixed and verified by the supplier. A syringe marked in small increments gives a more reliable measurement than one with coarse markings. The stated vial mass depends on the supplier's testing, which our guide to certificates of analysis covers.
This guide does not cover administered quantities. Concentration is a property of a solution. What quantity of that solution is appropriate for any purpose is outside the scope of this site, and no supplier of research-use material can advise on it.
How to mix a peptide without damaging it
Technique affects the result.
Wipe the vial stopper with an alcohol swab and let it dry before inserting anything through it. The stopper is not sterile on its outer surface.
Add the diluent slowly, directing it against the inside wall of the vial rather than onto the powder directly. Peptides are sensitive to mechanical stress, and a jet of liquid striking the cake can damage the material.
Let the powder dissolve on its own. It usually takes a few minutes. If it needs help, roll the vial gently between your hands or swirl it. Do not shake it. Shaking creates foam, and where liquid meets air in foam, peptides lose their structure and are damaged.
Inspect the result. A properly reconstituted solution is clear. Cloudiness, visible particles, or material that has not dissolved after a reasonable period indicates a problem with the vial or the diluent.
Storing reconstituted peptides
A reconstituted solution needs refrigeration. This is the point at which a peptide moves from being a stable dry solid to being a fragile solution, and storage requirements change accordingly.
Sealed powder and mixed solution need different storage, and one instruction covering both would be wrong for one of them. Check the specification for the compound in use. Our guide to freeze-drying and storage covers the dry-state requirements in more detail.
Label the vial with the date of reconstitution and the resulting concentration. A row of identical vials with no dates is a common and avoidable source of error.
What degrades a reconstituted peptide
Four things break down a peptide in solution.
Time. Degradation begins immediately and continues. A solution weeks old is not the same as one prepared yesterday, whatever it looks like.
Temperature. Warmth accelerates every relevant reaction. Anti-doping research illustrates how quickly this can happen: in a 2026 study examining sample storage, BPC-157 in liquid serum degraded completely within a week at room temperature and at 4°C, while remaining detectable in dried form.1
Light. Ultraviolet light damages some of the amino acids in the chain. Vials should be kept dark.
Freezing and thawing. Freezing a solution forms ice crystals, and the crystals physically damage the peptide. Each freeze and thaw does more damage, so repeatedly freezing and thawing a solution is worse than either state on its own.
The damage is invisible. A solution that looks fine may have lost much of its intact peptide, which is one reason old solutions give unreliable results.
In our own operation, lyophilised stock is kept in freezers in line with the storage guidance for each compound, and no batch is held beyond twelve months. It is reconstitution that shortens shelf life, not time in the freezer, which is one reason research peptides are supplied lyophilised in the first place.
Common questions about peptide reconstitution
How much bacteriostatic water should be added to a 5mg vial?
There is no single correct volume. Any amount that fully dissolves the powder produces a valid solution; what the volume changes is the concentration. Adding 2ml to a 5mg vial gives 2.5mg/ml. Adding 5ml gives 1mg/ml. The usual practice is to pick a volume that makes the resulting concentration a round, easy number, and to record it on the vial. What quantity of any solution is appropriate for any purpose is outside the scope of this site.
Can sterile water be used instead of bacteriostatic water?
It dissolves the powder just as well, but the resulting solution has a much shorter working life. Sterile water contains no preservative, so nothing suppresses bacterial growth once the vial has been accessed. Bacteriostatic water contains 0.9 per cent benzyl alcohol for exactly that reason. For a solution used once, immediately, the difference matters less; for a vial accessed over days or weeks, it matters a great deal.
How long does a reconstituted peptide last?
It depends on the compound, the diluent and the storage, and degradation is usually invisible, so a single shelf life cannot be given for every case. The reliable rules are that solutions are always less stable than sealed powder, refrigeration always extends working life, and light, warmth and repeated freeze-thaw always shorten it. Where the specification for a compound states a figure, that takes precedence.
Does unopened powder need the fridge?
Sealed lyophilised vials are the stable form and keep for a long time stored cold and dark; freezers extend that further. The specification for each compound states its storage requirement. The point at which storage becomes critical is after reconstitution, not before.
Common peptide reconstitution mistakes
Shaking the vial. The most common error. Foam damages peptides. Swirl or roll instead, or wait.
Firing the liquid straight onto the powder. A jet of liquid can damage the material. Direct it against the glass wall and let it run down.
Using the wrong liquid. Sterile water where bacteriostatic water was appropriate cuts the working life of the solution sharply. Where a supplier specifies a diluent, that specification exists for a reason.
No label. A row of identical vials with no dates or concentrations is a common and avoidable source of error. Label every vial with the date and the concentration at the time it is made.
Storing the solution at room temperature. Solutions need refrigeration. In a 2026 storage study, BPC-157 in liquid serum broke down completely within a week even refrigerated at 4°C, and dried material lasted far longer.1 Warm liquid storage is the worst combination.
Trusting appearance. A degraded solution usually looks identical to a fresh one. Time and temperature records tell more than looks do.
Specification and supply
Peptides supplied through this site are lyophilised powder, specified by mass, tested by HPLC, with a certificate of analysis issued per batch. Storage requirements differ between sealed and reconstituted material and are stated on each product page. Full range: research peptides.
Supplied for laboratory research use only. Not for human consumption.
References
- Mazzarino M, et al. Rapid and harmonized analytical workflow for the determination of peptidic and non-peptidic doping agents in dried and liquid blood matrices. Analyst. 2026. DOI