Priming a pen and whether the primed volume is wasted

Priming a pen and whether the primed volume is wasted Writing it up because I had to work it out twice and would rather nobody else did.

I have spent a fortnight trying to pin priming a pen down and I want to set out where I have got to, because I suspect the honest answer is duller than the thread this will produce.

What I have: a consistent observation across a small number of cases, collected the same way each time. What I do not have: any controlled comparison, or any reason to think my cases are representative.

The specific question is whether the pattern survives once the obvious confounder is removed. I cannot remove it with what I have.

Everything in the opening post holds. The case it does not cover is the one I have.

A pen that has been dropped may not be visibly damaged and may not deliver accurately afterwards. Manufacturers say to replace rather than to test, and there is no test a user can do.

Answering the question post #5 raises rather than the one it answers.

Disposal of a used pen is a sharps question even where the needle is retracted, and local rules vary more than people expect.

I am not the right person to answer the follow-up to this.

Dose counters: pens show the remaining number of doses. When the counter reaches zero, the pen is empty and cannot deliver more. Noting the counter before injection prevents running out unexpectedly.