Revisiting: Drawing from a pen cartridge with a syringe: how the risk profile changes

Revisiting: Drawing from a pen cartridge with a syringe: how the risk profile changes Writing it up because I had to work it out twice and would rather nobody else did.

Question about a metering device rather than about a syringe, because the failure modes are different.

The instruction leaflet is clear about priming and about the hold count at the end. It is silent about what I am asking, which suggests either that it does not arise or that it arises so rarely nobody wrote it down.

Which of those is it?

Off-label dosing with a pen: if you want to deliver a dose different from the pen's pre-set steps (e.g., halfway between two step doses), that is off-label use. Some pens allow it; others do not. Confirm before attempting.

That is the practical version. The rigorous version is longer and says the same thing.

The opening post and I disagree about the size of the effect, not about the direction.

Air in a cartridge behaves differently from air in a syringe because the mechanism displaces a fixed volume regardless. That is what priming addresses.

It cost nothing to check and would have cost something not to.