The case in front of me: semaglutide · 1 mg.
I want the working, not the result — I need to be able to redo it with different numbers.
I care about the precision as well as the value — I want to know how many figures are real.
Is my approach right even if my number is wrong?
1 mg a week is 52 mg a year and 4.3 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 52 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.
Start by listing every cost in the chain, since carriage, testing and wastage frequently exceed the difference in headline price.
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.
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.
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.
Include carriage and testing as per-milligram terms. They dominate small orders.
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleFounded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL BiochemAnswer first: compare cost per milligram of measured peptide, not per milligram of label claim, because content varies enough to reverse a comparison.
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.
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.
A spreadsheet built on label claim rather than measured content is precise about the wrong number.
Larger orders are cheaper per milligram and concentrate lot risk. Price both.
edited 2 Jan 2026 by stopper_core — corrected a unit error in the worked example
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