Fiasp “Penfill” revisited

I’ve written in the past about the fact that Fiasp is not available in Penfill format in Australia, and this is still the case.


NovoRapid is available in 3 formats:

  • 10 mL vials intended for syringe and pump use.
  • Disposable 3 mL FlexPens.
  • 3 mL Penfill cartridges which can be put into pens like the NovoPen 4 and the NovoPen Echo. Some people still use the NovoPen 3.
    The Echo lets you do doses to the nearest 0.5U, and also displays the last dose and how long ago it was.

Fiasp is only available in 10 mL vials and in disposable 3 mL FlexTouch pens. The Penfills that are available overseas are not subsidised through PBS and thus Novo don’t import them.

As I noted back in 2019, people worked out fairly quickly how to convert a FlexTouch pen into a “Penfill” so they could use it in a NovoPen. I showed doing it by cutting the red end of the pen so the glass cartridge came out.

It’s all in the wrist

Cutting the end of the pen is needed if the pen has been partly used, but there is a quicker and easier way if the pen is unused. As long as the piston hasn’t started progressing down the pen, it can be (carefully) broken in half, and the glass cartridge just slides out.

After a recent discussion online about this technique I decided to film it and hopefully cover all the details.


I tend to convert a batch of pens all at once, and quickly put the cartridges into a small sealed Decor/Tupperware/whatever box to keep them clean and together back in the fridge.

Just to repeat the (hopefully) obvious:

This is entirely unofficial technique and if you do this yourself then you’re accepting all responsibility for going “off-label”.

When I’m using Fiasp I still keep it in cartridge format even if I’m filling a pump, so I have the option of dropping it into a pen for emergencies.

6 thoughts on “Fiasp “Penfill” revisited”

  1. Awesome – thank you for that, I didn’t realise it was possible to do that and i have been missing my half doses and memory function!.

  2. I’ve just come across this, you definitely need to very careful when bending the pen. Cracked my first vial 🙂 then grabbed some of the 3d printer snips for cutting filament and cleaning prints, and cut the measurement plastic either side, worked an absolute treat. Cheers.

    1. Yes. I tried at one point leaving the cap on the pen but it put pressure in the wrong spot. If I’m careful to bend it at 90˚ to the glass facing “up”, and have my thumb acting as a fulcrum right up against the joint then it works reliably.

  3. I have quite a few fiasp disposable pens I’d like to convert to a refill but I don’t have any of the little caps from old refills. Can I get these somewhere or is there an alternative.

    1. I get mine from Penfills for other insulins.
      I think some people have cut the end off pens and fashioned them into something similar. But I’m not sure how to do that and maintain a secure connection in the NovoPen.

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