Pen wastage and its effect on real cost Writing it up because I had to work it out twice and would rather nobody else did.
Two things I would like separated before anyone answers on pen wastage, because they get bundled and then argued about as one thing.
The first is descriptive: what has actually been observed, by whom, and how. The second is causal: why. I am asking about the first only.
The opening post is right about the mechanism and I think understates the practical bit.
Independent testing is a real cost and belongs in the comparison. A cheaper supplier tested every lot may cost more in total.
This is the sort of thing that ought to be settled and apparently is not.
A pen and a vial are not the same product. Dead volume, wastage and the number of doses actually obtainable all differ.
One caution on pen wastage: everything above assumes the underlying documentation is what it claims to be. That assumption is doing real work and is rarely stated.
Post #5 describes the usual case. This is about the unusual one.
The cost of an independent submission is worth stating in these threads, because it is the main reason people do not do it.
It cost nothing to check and would have cost something not to.
Cost per milligram is the only comparison that survives format differences, and even then it needs care.
Where I part company with post #5, and it is a narrow parting.
Compute cost per delivered dose at your dose if you want a number you can act on. That requires knowing your dose, vial volume, and whether you are using a vial or a pen.
Prices in old topics are historical records and are frequently wrong now. Every post here carries its date for that reason.
Pharmacy acquisition cost: a pharmacy pays less than the patient pays, even at insurance rates. That margin is where the pharmacy's costs and profit live.
Picking up post #14: that is the part I would want checked first.
Landed cost including shipping, fees and currency conversion is what you actually pay, and quotes that look identical frequently are not.
One of those cases where knowing the mechanism does not help the decision.
Cost per week at a maintenance dose is the figure most people actually want and least often calculate.
Small methodological point on pen wastage: repeating a measurement is cheap and resolves most of what is being argued about here at no cost to anyone.
I had written a reply contradicting post #16 and deleted it. Here is what survived.
Cost per milligram is the only comparison that survives format differences, but even then it needs care. A pen and a vial are not the same product and cannot be compared on price per milligram alone because dead volume, wastage, and number of doses actually obtainable differ.
I would treat that as a working assumption and revisit it.
Where somebody posts a comparison, the useful version states the date, the region and what was included.
Post #17 and I disagree about the size of the effect, not about the direction.
A cheaper option that arrives slowly has a cost in the form of running out, and people rarely price that.
Independent testing is a real cost and belongs in the comparison. A cheaper supplier tested every lot may cost more in total.
Wastage from a concentration choice that leaves an unusable remainder is a real cost and is invisible in a per-milligram figure.
That is the shape of it. The detail is where I would expect to be corrected.
Worth separating two things that post #21 runs together.
Compute cost per delivered dose at your dose if you want a number you can act on. Everything else is a comparison of packaging.
Not a strong opinion, just a consistent one.
I came in to disagree and I am leaving without a disagreement.
Cost per milligram is the only comparison that survives format differences, and even then it needs care.
It is the sort of thing that seems obvious in retrospect and was not at the time.
Compute cost per delivered dose at your dose if you want a number you can act on. That requires knowing your dose, vial volume, and whether you are using a vial or a pen.
Written quickly, so the reasoning may be tighter than the wording.
Prices in old topics are historical records and are frequently wrong now. Every post here carries its date for that reason.
Noting that the question and the thing people usually mean by it are different.