What an injection pen does
This guide covers the reusable pen that you fill yourself. The pens sold per peptide in the shop arrive filled, primed and sealed; the pre-filled pen guide covers those.
An injection pen holds a cartridge of solution and dials out a set number of units at a time. Compared with drawing from a vial with an insulin syringe, there is no drawing step, no air bubble to chase and nothing to read off a 1 ml barrel: the dose window shows the number and the pen delivers it. The needle is a short, fine 32G pen needle that screws onto the front.
Peptides do not come in pens. They arrive as a freeze-dried vial, are reconstituted with bacteriostatic water, and the solution is then transferred into a 3 ml pen cartridge. That transfer is the only extra step, and it is what the luer lock syringes in the pen kit are for.
What is in the kit
The pen kit is everything needed to go from a reconstituted vial to a loaded pen. Each part is also sold on its own for restocking.
- Reusable pen V2, which takes 3 ml cartridges.
- 3 empty 3 ml cartridges, one per vial.
- 12 pen needles, 32G and 4 mm, one per injection.
- 20 alcohol wipes for the vial stopper, the cartridge septum and the skin.
- 5 luer lock syringes of 3 ml, each with its own needle, and 5 vent needles for filling cartridges, with spares for a transfer that goes wrong.
Filling a cartridge
- Reconstitute the vial as usual and let it dissolve completely. See the reconstitution guide for the full steps.
- Wipe the vial stopper and the rubber septum at the top of the empty cartridge with alcohol and let both dry.
- Draw the whole solution out of the vial with a 3 ml luer lock syringe, using the needle it comes with.
- Push a vent needle through the cartridge septum so the air inside can escape while it fills.
- Push the syringe needle through the septum next to it and inject the solution slowly down the inside wall. Do not force air in afterwards.
- Withdraw both needles, label the cartridge with the peptide, the concentration and the date, and refrigerate it or load it straight into the pen.
Loading, priming and dialing
- Unscrew the pen's cartridge holder, slide the filled cartridge in with the septum towards the front, and screw the holder back on.
- Screw a new pen needle on, pull off both caps, and keep the outer cap for removing the needle later.
- Prime: dial 2 units and press the button with the needle pointing up until a drop appears at the tip. Repeat if no drop shows. This removes the air between cartridge and needle.
- Dial the dose. The pen counts in units, and on this scale one unit is 0.01 ml, the same as an insulin syringe. The peptide calculator converts a concentration into units.
- Hold the button down for a slow count of ten after the dial returns to zero before withdrawing, so the full dose leaves the needle.
- Unscrew the needle using its outer cap, discard it in a sharps container, and recap the pen.
Storage and travel
A loaded pen is stored like a reconstituted vial: in the fridge at 2 to 8 °C, out of the light, with the needle removed, and used within 28 days of filling the cartridge. Never freeze it. Spare filled cartridges keep the same way.
For a day out or a trip, the insulated pen case with its two gel ice packs keeps a pen cool for the hours between fridges. Freeze the gel packs, not the pen, and keep the pen from direct contact with a pack so the solution does not freeze.
Common mistakes
- Skipping the prime, which delivers air instead of the first part of the dose.
- Leaving a needle on the pen between injections.
- Reusing a pen needle; the tip blunts and the injection hurts more.
- Mixing up cartridges because they were not labelled.
- Carrying the pen in a pocket or a hot car instead of the insulated case.
Frequently asked questions
- How much fits in a cartridge?
- The cartridge is filled from a reconstituted vial, so a 3 ml cartridge takes the 2 ml of one vial with room to spare. One cartridge is one vial; the three cartridges in the kit cover three vials.
- Do I really need a new needle every time?
- Yes. Pen needles are single use: the fine 32G tip blunts after one puncture and a used needle left on the pen lets air in and solution out. Unscrew it after each injection and put the pen away without a needle.
- Reusable or disposable pen?
- The reusable pen takes a new cartridge each time one is empty and lasts for years. The disposable pen is a one-cartridge device for a single vial, useful for travel or a trial run before buying the reusable one.