What you'll need

To access a vial cleanly you only need a few items: the bacteriostatic water vial itself, an alcohol prep swab, and a sterile syringe with an appropriate needle for the volume you intend to draw. A flat, clean working surface helps keep handling tidy.

Step 1 — Inspect the vial

Check the vial before opening. The glass should be intact, the solution should be clear, and the small metal flip-off cap on top of the vial should be present and undisturbed. The cap is a tamper-evident seal, so if it is missing or already lifted, do not use the vial.

Step 2 — Remove the flip-off cap

The plastic flip-off cap sits on top of a metal ring crimped around the rubber stopper. Use a thumbnail or the edge of a fingernail under the lip of the cap and lift it off — it pops away easily and exposes a small circular area of rubber stopper in the centre. Do not try to remove the surrounding metal ring or the rubber stopper itself; those keep the vial sealed.

Step 3 — Swab the stopper

Wipe the exposed rubber stopper with a fresh alcohol prep swab and allow it to air dry for a few seconds. This step reduces contamination risk and should be repeated before every draw, not just the first one.

Step 4 — Draw fluid through the stopper

Attach a needle to your syringe, pull air into the syringe equal to the volume you intend to draw, and insert the needle through the centre of the rubber stopper. Invert the vial so the stopper points down, push the air in, then draw the required volume of bacteriostatic water back into the syringe. Withdraw the needle straight out.

Step 5 — Store the vial after use

After the first puncture the rubber stopper reseals itself, but the vial is now considered "opened". Store it at room temperature or in the fridge, mark the puncture date on the label, and discard the vial 28 days after first puncture. See our storage guide for the full handling routine.

Common questions