Mixing a powder with sterile water

General information about the equipment, not medical advice. The directions that came with your medicine and the person who prescribed it come first, every time.

What we do and do not supply

We sell bacteriostatic water, sterile water for injection, vial adapters, drawing-up needles, syringes and swabs. We do not sell peptides, hormones or any prescription medicine, in any form, and we are not going to tell you what to put in the vial or how much of it to use.

This page is about the equipment and the arithmetic. Everything specific to a compound comes from whoever is managing your treatment.

Bacteriostatic water and sterile water are different

Sterile water for injection is exactly that and nothing else. Once you pierce the stopper it is a single use product, because there is nothing in it to stop bacteria growing.

Bacteriostatic water contains benzyl alcohol, usually around nine tenths of a per cent, which inhibits bacterial growth and allows a vial to be entered more than once over a period of days. That is what makes a multi-dose vial practical.

Benzyl alcohol is not suitable for everyone, and which diluent is right is part of the prescribing decision rather than a preference.

The volume you add sets the concentration

This is the part people get wrong. The powder is a fixed amount. The liquid you add is what changes, and it determines how much powder ends up in each unit on the syringe.

Put simply: add twice as much water and every mark on the barrel is worth half as much. Nothing about the powder changed. Which is why the volume has to be the one you were told to use, and why writing it on the vial matters.

Our reconstitution calculator does the arithmetic if you have the strength and the volume. It does not tell you what either of them should be.

Keeping the vial clean

Swab the stopper before every entry and let it dry. Every time, not just the first.

Add the water slowly, down the inside wall of the vial rather than straight onto the powder. Then swirl or roll it gently until it dissolves. Do not shake it. Many of these compounds are fragile and shaking is what foams and damages them.

A vial adapter seats once in the stopper and gives you a clean luer port to work through, which means you are not pushing a needle through the same piece of rubber over and over. On a vial you will enter many times it pays for itself in coring alone.

Label it. Date, what is in it, and the volume you added. In a month you will not remember, and guessing is not an option.