Retest dates and shelf life on research peptides, explained

Written 23 September 2026, last changed 7 October 2026 by the trade desk. About 4 minutes to read.

A retest date is the date by which a batch is analysed again before it is used further; an expiry date says the material should no longer be used. Every batch here carries a retest date on its batch record rather than an expiry, and the shelf life is 24 months from manufacture.

Shelf life

Twenty-four months from manufacture: for lyophilised lines held at minus 20 degrees Celsius, for HCG and HMG at 2 to 8 degrees or minus 20 as the desk confirms for a batch, for the solution lines held at 2 to 8 degrees, and for bacteriostatic water and vitamin B12 held at room temperature. The figure is the period over which the batch is certified to meet its specification if stored as stated.

The retest date

The date on which the batch is due to be analysed again before it is sold on. It is not a cliff. A batch a day past retest has not changed overnight; it has reached the point where its certification needs fresh data.

What happens on our shelf

Stock past its retest date is removed from sale automatically and cannot be shipped. A batch is re-analysed against the same specification; if it passes, a new retest date is set and a new certificate records the retest; if it fails, it is withdrawn. The number of retest cycles is capped, because a batch cannot be re-certified for ever.

What it means for stock you hold

Keep the certificate with the batch. Past the retest date, either have the material re-analysed or treat it as no longer certified. Storage conditions, set out in storing and handling lyophilised peptides, matter more than the calendar: a vial that has been through a freezer failure is not covered by any date.

Why the date is not simply longer

A peptide in a dry cake at minus 20 degrees changes very slowly, but it does change, and the sequences most at risk are the ones with residues that oxidise or deamidate. Twenty-four months is the shelf life the specification sets for every line we carry, not the period after which a vial is spent. Extending it would mean a longer study for each line, and the retest mechanism does that job one batch at a time instead.

Reading the dates: batch number, certificate, batch record

The month of manufacture is in the batch number: L2607 is July 2026. The certificate carries the date of analysis. The retest date is on the batch record, which the desk gives for any batch number: the manufacture date plus the shelf life, or, after a re-analysis, the date of that analysis plus a new period, and a re-analysed batch has a certificate of its own.

Picking order

Stock is picked oldest in-date batch first, so the batch that reaches you is the one that has been on the shelf longest and is nearest its retest date, while fresher batches wait their turn. No batch ships past its retest date. If a laboratory needs the longest possible remaining period for a planned study, say so on the order and the desk will pick a fresher batch.

Applies to

This guide was written with Semaglutide in mind, and it holds for the other lines of its kind; the full list is on the compounds page.

Questions about dates and shelf life

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