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Buying 3 min read

Where to buy bacteriostatic water in the UK

Bac water is the least glamorous item on a peptide order and the one most often bought carelessly. It goes into every vial it touches, so it deserves the same checks as the peptide.

HP Written by the Hello Peptides lab team · Updated October 2026

The short answer

In the UK, bacteriostatic water is bought online, from laboratory suppliers and from peptide suppliers. It is a laboratory and clinical supply, not a retail product, so it is not something high-street chemists keep on the shelf.

Can you buy it at Boots or a pharmacy?

People search for bacteriostatic water at Boots and other chains, usually after finding that a peptide order needs it. It is not part of a normal pharmacy range. What a pharmacy is more likely to offer is sterile water or saline in single-use ampoules, which is a different product: see the table below.

What genuine bac water looks like

  1. 01
    0.9% benzyl alcohol on the labelThat is the preservative, and it is what makes the water bacteriostatic. If the label does not state it, it is not bac water.
  2. 02
    A sealed, multi-use vialA glass or plastic vial with a rubber stopper under a tamper-evident cap. The stopper is what allows repeated draws.
  3. 03
    A batch number and an expiry dateBoth printed on the vial, not only on the outer box.
  4. 04
    A stated volumeMost often 10ml or 30ml. Buy the size you will use within the period the label allows once opened.
  5. 05
    Clear and colourlessAny cloudiness or particles means the vial should be discarded.

What not to use in its place

AlternativeWhy it is not the same
Sterile waterSterile but unpreserved. It is single-use, and a peptide reconstituted with it keeps for days, not weeks
SalineSterile salt solution. A different solvent, and not what most reconstitution methods specify
Distilled or deionised waterPure but not sterile
Tap or bottled waterNeither pure nor sterile

What is bacteriostatic water? explains the difference the preservative makes.

How much you need

Less than most people buy. A typical lyophilised vial is reconstituted with between 1ml and 3ml, so a single 10ml vial of bac water covers several. The peptide calculator shows the concentration each volume gives, and reconstituting a lyophilised vial sets out the method.

Do you need it at all?

Only for lyophilised peptides. Everything in our range is supplied pre-mixed, already in solution, so none of our peptides needs bac water or any preparation.

Buying it from us

We list bacteriostatic water for laboratories that also work with lyophilised peptides. It is not yet released. Send us a message and we will tell you when it is in stock.

Storing it

Keep unopened vials at room temperature and out of the light. Write the date on the vial when you first puncture it, and follow the label for how long it may be kept after that.

Research use onlyProducts are supplied for laboratory research and are not for human or animal consumption, diagnosis or treatment. Questions about a batch? Contact the lab with the batch number.
Keep reading All guides →
Compounds What is bacteriostatic water? Sterile water with a preservative, used to reconstitute lyophilised peptides: what it is and when you need it. 2 min read Preparation Reconstituting a lyophilised vial Water, volumes and the concentration maths, with a calculator. 6 min read Tools Peptide reconstitution calculator Work out the concentration of a reconstituted vial from the peptide mass and the water added. 3 min read
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