Filling a pen cartridge
Pens · 5 min read
Plan it
Open the Pen calculator with your vial, water and dose. It tells you how much to load, the clicks per dose, how many doses the cartridge holds and how long it lasts. Aim for a cartridge you'll finish within about 28 days.
Mixing a vial with 3 mL of water means one vial fills one cartridge exactly.
You need: the mixed (and ideally filtered) peptide, an empty sterile 3 mL cartridge, a 3 mL luer-lock syringe with a 25–27G needle (or 1 mL insulin syringes, 100 units per load), a venting needle, alcohol pads and a label.
Which way does your cartridge fill?
- Plunger at the back (open) end: the cartridge is full of air. It needs a venting needle so the air can get out as the liquid goes in.
- Plunger pushed up near the septum: the liquid pushes the plunger back as it fills. No venting needle.
Steps
- 1Wash your hands. Swab the vial stopper and the cartridge septum (the rubber in the metal cap). Let them dry.
- 2Draw the planned amount from the vial.
- 3Hold the cartridge septum up. If it needs venting, push the venting needle just through the septum so its tip stays near the top.
- 4Push the filling needle through the septum beside it and press slowly, letting the liquid run down the glass. Stop before the liquid reaches the venting needle's tip.
- 5Take the filling needle out first, then the venting needle. Both go in the sharps container.
- 6Tap the cartridge and check it: clear, nothing floating. A small air bubble is normal; priming removes it.
- 7Label the cartridge: peptide, concentration, date filled.
- 8Load it into your pen and prime it (see Using a reusable pen).
Never fill past 3 mL, and never refill a used cartridge. When it's empty, it goes in the sharps container.
Go with this guide
Pen calculatorGeneral how-to information, not medical advice. Follow your prescriber's instructions where they differ.