The particulars: tirzepatide · 5 mg.
I would rather understand the derivation than memorise the outcome.
Two people I asked gave two answers that differ by a factor of ten, which is suggestive.
Can someone show the working rather than just the answer?
Mechanically, evaluate a supplier on the documentation they cannot fabricate cheaply, which in practice means lot-specific certificates from a laboratory that hosts its own reports and a testing history that spans more than one lot.
The diagnostic red flags, in rough order of how much they tell you: a certificate whose lot number does not match the vial; a certificate with no method section; a purity figure quoted to two decimal places with no chromatogram; a testing date that precedes the stated manufacturing date; identical certificates across nominally different lots; and "sterile filtered" offered in place of a sterility test. Each of those is a specific inference, not a vibe.
| Step | Value | Note |
|---|---|---|
| Vial price, 10 mg nominal | £34.00 | As advertised |
| Nominal cost per mg | £3.40 | 34 ÷ 10 |
| Measured content | 9.2 mg | Independent content assay |
| Cost per actual mg | £3.70 | 34 ÷ 9.2 |
| Dead-space loss, 20 draws | 4 % | 80 µL of a 2 mL fill |
| Cost per delivered mg | £3.85 | 3.70 ÷ 0.96 |
| First vial, with £110 assay | £14.85 | Testing dominates a single vial |
A defensible group-buy structure has three properties: the material is tested before it is split, the test is paid for from the pool rather than by the organiser, and the split is documented with photographs and a per-participant record of lot, volume and date. If any participant can reconstruct what they received from the records, a later dispute is resolvable. If not, it is not.
The published aggregate datasets from Janoshik, Medutest and PeptideMeter are the closest thing to a systematic evidence base in this space, and the striking pattern across all three is that identity is almost always confirmed, purity is usually acceptable, and content is where the variance lives.
Worth being explicit that this site sells nothing, is not affiliated with any supplier, and has no financial relationship with any vendor discussed. Vendor storefronts are linked from the vendor directory, marked nofollow and sponsored.
Test the first lot from any new supplier, set your accept threshold before the result arrives, and keep the certificate with the lot number and the date in one place.
edited 21 Oct 2025 by bufferline42 — added the placebo-arm figures
Aggregated, published test results and vendor ratings built from submitted batches. Methodology stated, dataset browsable, no listing fees.
Browse resultsAsk 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.