A pen that felt like it delivered nothing: diagnosing it afterwards posts 31–40

Coming back to post #29, because the follow-up matters more than the original answer.

Priming: most pens require priming before the first use (injecting a small amount to fill the needle and line). Not priming can result in no dose being delivered on the first injection.

I disagree with the reply above, and I think the disagreement is substantive rather than terminological.

The distinction being drawn does not survive when you look at the published data for this specific question. I would be glad to be shown wrong on this, because the version I am arguing against is more convenient.

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.

post #33 answers the question as asked. The question underneath it is different.

Reusability: some pens are single-use (throw away after one injection). Others can be reused until empty. Confirm which type you have. Reusing a single-use pen is ineffective because the mechanism does not reset.

Visibility of the dose: some pens allow you to see the insulin remaining; others do not. Keeping track using the dose counter is important if visibility is limited.

Needle installation: some pens require a fresh needle for each injection; others have a single needle that stays attached. Check the design of your pen.

Worth separating two things that post #33 runs together.

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.

post #37 is right about the mechanism and I think understates the practical bit.

Reusability: some pens are single-use (throw away after one injection). Others can be reused until empty. Confirm which type you have. Reusing a single-use pen is ineffective because the mechanism does not reset.

Injection duration: most pens deliver the dose over several seconds. Holding the button down for the full duration ensures complete delivery. Releasing early can result in underdosing.

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.