Lot numbers and expiry dates on veterinary products: what they mean
· medixanimals
A lot number identifies a specific production run. An expiry date tells you the last day the manufacturer supports the product's stated characteristics. Together they are how a veterinary medicine, a supplement or a laboratory reagent is traced from the factory to the animal or the bench.
Why a lot number is not just a serial number
A serial number identifies one unit. A lot number identifies every unit made under the same conditions, from the same input materials, on the same equipment. That distinction is what makes a recall workable: when a manufacturer withdraws a lot, the question "which customers received a unit from this lot?" has to be answerable.
For that answer to exist, the lot has to be recorded at three points:
- Receiving — the lot number and expiry date are captured when the goods arrive, not later.
- Allocation — the specific lot each order line is filled from is recorded.
- Shipping — the lot number that physically left the warehouse is stored on the shipment.
If any of those three is missing, a recall becomes a manual reconstruction from paperwork.
FEFO, not FIFO
General warehousing usually picks first-in-first-out: the oldest stock leaves first. For dated goods that rule is wrong. The correct rule is first-expired-first-out: the unit with the earliest expiry date leaves first, regardless of when it arrived.
The two rules disagree more often than people expect. A shipment received in March with a two-year shelf life should be dispensed after a shipment received in January with a six-month shelf life, even though the January stock is "newer" on the shelf in no sense at all. FIFO would hold the short-dated stock until it expired.
Minimum remaining shelf life
Shipping a product the day before it expires is technically within date and practically useless. A laboratory that runs a reagent over a six-week study needs the reagent to be in date for six weeks.
This is handled with a minimum remaining shelf life rule: a lot is only eligible for an order if it will still be in date for an agreed period after delivery. The figure varies by product type and by customer agreement, and it is a genuine constraint on allocation, not a guideline — a lot that fails it is skipped even when it is the earliest-expiring stock available.
What to check when stock arrives
- The lot number on the outer carton matches the packing document. If they differ, the receiving record will be wrong from the start.
- The expiry date is legible and matches what was ordered. Some products are supplied with a manufacturing date and a shelf-life period rather than a printed expiry; the expiry has to be calculated and recorded, not left implicit.
- Temperature-sensitive items arrived within their range. A refrigerated product that spent a day at ambient temperature is not simply "a bit warm"; its expiry date no longer describes it.
- Damaged or partially opened packaging is quarantined, not shelved. Once a unit is mixed into general stock, the decision to use it has already been made by default.
Expired stock
Expired stock should be physically and logically separated. "Logically" matters as much as "physically": if expired units remain allocatable in the system, someone will eventually allocate them. The safer design blocks expired lots from allocation automatically rather than relying on a picker noticing the date.
This article is general information about inventory practice for dated goods. It is not veterinary advice and does not describe the storage or handling requirements of any specific product. Always follow the manufacturer's instructions and consult a licensed veterinarian about the care of an animal.