Research peptides break the usual inventory assumptions in two ways: lead times are long and variable, and the material degrades while it waits. Standard reorder arithmetic handles the first and ignores the second, which is why peptide inventories tend to drift toward overstocking.
The basic reorder point
A reorder point is the stock level at which a new order must be placed to avoid running out before it arrives. It is consumption during the lead time, plus a buffer for the variability of both.
Written plainly: average weekly use, multiplied by lead time in weeks, plus a safety buffer. A compound used at two vials a week with a four-week lead time has a reorder point of eight vials plus buffer.
Where degradation changes the answer
The usual response to a long lead time is to hold more stock. For material with a finite usable life that buys exposure rather than security: stock held beyond its usable window was purchased at full price and delivers nothing.
So there is a ceiling as well as a floor. The ceiling is the quantity that can be used within the material's usable window under realistic consumption.
| Input | Where it comes from | Common error |
|---|---|---|
| Average consumption | Your own usage log | Estimated from memory rather than measured |
| Lead time | The supplier, for in-stock versus made-to-order | Using the in-stock figure for everything |
| Lead time variability | Order history | Assumed to be zero |
| Usable window | Retest date and storage conditions | Treated as indefinite |
| Minimum order | The supplier's quote | Forces overbuying on low-use items |
Five inputs. Three of them come from your own records rather than the supplier.
When the minimum exceeds the ceiling
This is the common and awkward case: the smallest order you can place is more than you can use before the material ages out. There are three honest responses, and buying it anyway is not one of them.
- Order less often and accept the gaps, if the work tolerates them.
- Consolidate across compounds so one order clears the minimum, which minimum order quantities covers.
- Reconsider whether the compound belongs in the formulary at all, which is the argument in building a research peptide formulary.
What to review, and how often
Quarterly is usually enough. Three questions: which items were ordered on an emergency basis, which items were discarded unused, and which items have not moved at all. The first says the reorder point is too low, the second says the ceiling was exceeded, and the third says the item may not need stocking.
The two numbers that are usually guessed
Consumption and lead-time variability. Both are routinely estimated from memory, and both are available from records you already hold if anyone looks: the usage log gives the first and the order history gives the second.
The difference matters because a reorder point built on a remembered consumption rate is wrong in whichever direction the memory was, and nobody finds out until there is either a stockout or a shelf of material nobody can use. One quarter of actual measurement replaces the guess permanently.
Consignment and held stock
Where a compound is used steadily but unpredictably, some suppliers will hold stock against a standing arrangement rather than shipping it. That moves the storage risk back up the chain, which is where it belongs for material that degrades.
It is worth asking about on exactly the items where your ceiling sits below the supplier minimum, because it solves that specific problem without anyone buying material they cannot use. Minimum order quantities covers why that mismatch arises.
First expiry, first out
Where several lots of one compound are held, draw on the one closest to its retest date rather than the one at the front of the tray. That requires lot-level visibility in storage, which is a labelling problem before it is an inventory problem. Labeling and identification covers making the date readable without handling each vial.
For how this fits with everything else that happens to a vial between delivery and use, peptide storage and handling for clinics covers the full picture.