What I have: a GLP-1 receptor agonist · 10 mg.
I can do the algebra. I am not confident about the conversion factors.
If there is a standard way to lay this out, I would rather learn that than invent one.
What is the general form of this calculation?
10 mg a week is 520 mg a year and 43.3 mg in an average month — put every route on that denominator before comparing anything. Cost per milligram is the only figure that survives the comparison, because the presentations differ: a licensed pen prices a dose, a compounding pharmacy prices a vial, and a research supplier prices a mass. Divide each one's twelve-month cost by 520 mg and the three become the same number in the same unit. Then add what the cheapest route does not include — independent purity and content testing, the vials you discard, and the postage — because a route that needs testing to be trustworthy has that testing in its cost per milligram whether you account for it or not.
The short version: unit price, carriage, testing, dead-space loss and wastage. The first is the one everybody compares and rarely the one that decides it.
Independent testing costs roughly the price of one to two vials at the services this community uses. On a two-vial order that is a fifty to a hundred per cent surcharge; on a twenty-vial order it is five per cent.
In practice, carriage amortises across the order. Twenty-five pounds of carriage on one vial is £2.50/mg on a 10 mg vial; on ten vials it is £0.25/mg. That single term explains most of the case for larger, less frequent orders.
Published content assay results across the independent services show nominal and measured content differing by one to ten per cent, which is the term that makes label-price comparisons unreliable.
The caveat is that optimising cost per milligram optimises for the wrong thing if documentation and consistency are what you actually need.
Fixed-needle syringes save more peptide than most price differences do.
edited 22 Oct 2024 by t_oyelaran — clarified the distinction between purity and content
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsThe relevant arithmetic is that a fifteen per cent price advantage disappears against a ten per cent content shortfall plus a testing cost.
The full calculation: (unit price + carriage share + testing share) ÷ (nominal mg × measured content fraction × (1 − dead-space and wastage fraction)). Every term after the first is routinely omitted.
It helps to be literal here: wastage from a reconstituted vial discarded at the end of its in-use period is a genuine cost, and it is a function of the diluent volume chosen at reconstitution rather than of anything the supplier did.
A spreadsheet built on label claim rather than measured content is precise about the wrong number.
Include carriage and testing as per-milligram terms. They dominate small orders.
edited 22 Oct 2024 by g_paskevicius — added the citation requested in comments
Answer first: compare cost per milligram of measured peptide, not per milligram of label claim, because content varies enough to reverse a comparison.
Change one number and it reverses: if B assays at 82 per cent, that is 8.2 mg for £52, or £6.34/mg, and the cheaper vial is now the more expensive peptide.
Dead-space loss is small with fixed-needle insulin syringes — a few microlitres per draw — and substantial with detachable-needle luer syringes at 35 to 100 microlitres. Across twenty draws that is up to two millilitres of solution.
Syringe dead-space volumes are published per design, with fixed-needle insulin syringes under 5 microlitres and conventional luer designs at 35 microlitres or more.
Divide by measured content, not by label claim. That is the whole correction.
Answering this needs the order size, because carriage and testing amortise very differently across one vial and across ten.
Cost per milligram is the wrong metric entirely if you are optimising for confidence rather than price, and it is worth saying which one you are doing before you build the spreadsheet.
Larger orders reduce cost per milligram and increase exposure to a single lot, which is a real trade rather than a free win.
Decide whether you are optimising cost or confidence before you build the model.
Start by listing every cost in the chain, since carriage, testing and wastage frequently exceed the difference in headline price.
Worked example. Supplier A: £60 for a 10 mg vial, content 96 per cent, so 9.6 mg for £60, or £6.25/mg before carriage. Supplier B: £52 for the same nominal vial, content 88 per cent, so 8.8 mg for £52, or £5.91/mg. B still wins here, but the gap has narrowed from thirteen per cent on the label to five per cent in reality.
Carriage on international consignments scales sub-linearly with weight, which is the quantitative basis for order consolidation.
Larger orders are cheaper per milligram and concentrate lot risk. Price both.
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.