Priming a pen and whether the primed volume is wasted — one year on

Posting this under the heading it deserves: Priming a pen and whether the primed volume is wasted — one year on Everything below is what sits behind that.

Practical question with the units stated, because I have seen how quickly these go wrong without them.

I have a 5 mg vial of tirzepatide and I am working to a 0.5 mg step. My syringes are U-100 insulin syringes, 0.3 mL barrel.

I can do the arithmetic and I have done it twice, getting the same answer both times, but I would like someone to check the reasoning rather than the number — specifically whether I have thought about the residual volume correctly, and whether the graduation I am landing on is one a person can actually read.

On the opening post — agreed on the reasoning, with one qualification.

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.

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.

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.

Worth separating two things that post #2 runs together.

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.

This follows post #4 rather than contradicting it.

Pen confusion between compounds: if you are using multiple pens or alternating pens, confirming you have the correct pen before injection prevents administration errors. Check the label every time.

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.