Second pass at: A pen that felt like it delivered nothing: diagnosing it afterwards

Second pass at: A pen that felt like it delivered nothing: diagnosing it afterwards — setting out what I have, and where I think it stops being reliable.

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?

The opening post answers the question as asked. The question underneath it is different.

A pen delivers a fixed or dialled dose from a cartridge and is a metering device rather than simply a covered syringe. That is why dose changes are constrained to whatever the mechanism supports.

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

Storage after first use: most pens can be stored at room temperature after first use, even if unrefrigerated, for a limited time (often 28 days). Check your specific pen's labelling.

Reading rather than answering, but this is the post I would point somebody at.

Coming back to post #3, because the follow-up matters more than the original answer.

Comparing cost per milligram between a pen and a vial ignores wastage, dead volume and the number of doses actually obtainable. Cost per delivered dose at your dose is the comparison that survives.

Post #3 is right about the mechanism and I think understates the practical bit.

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.

Holding the pen in place for the stated count after the plunger stops is the manufacturer's answer to leakage at the site. It is on the instruction leaflet and it is the step most often skipped.

The claim is narrower than it sounds, and deliberately so.

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

A partial answer, offered because a partial answer beats none.

Travel with a pen raises a cold-chain question and a documentation question. The second is the one people forget until an airport.

I would want to see it done twice before believing it once.

Narrowing post #8, because the general version has more than one answer.

A pen that will not dial to the intended dose is usually telling you the cartridge does not contain enough for it. That is a designed behaviour rather than a fault.

I would rather be precise about what I do not know than vague about what I do.

Nothing here is medical advice, and pen technique is the single easiest thing to have demonstrated in person rather than learned from a description.

Filing this under things that are true until someone shows me otherwise.

Storage instructions for a pen typically differ before and after first use, and the in-use period is the one people miss. It is on the carton.