First expiry first out, usually shortened to FEFO, is a stock rotation rule that ships the unit with the nearest expiry date before any other unit of the same product, regardless of which one arrived at the warehouse first. A vaccine vial that arrived last week but expires next month goes out ahead of a vial that arrived last month but expires next year.
This runs opposite to the more familiar first in first out rule used across most ordinary warehousing, where the oldest arrival simply ships first on the assumption that arrival order and expiry order are the same thing. In cold chain and pharmaceutical storage, they frequently are not.
Arrival order and expiry order diverge
A shipment's expiry date is set by its manufacturing date and its labeled shelf life, not by when it happens to reach a given warehouse. A batch made two months ago can carry a longer remaining shelf life than a batch made four months ago if the second batch has a shorter total shelf life to begin with, or if it sat in transit or storage elsewhere before reaching the same shelf. First in first out would ship the wrong one first in either case.
Vaccines, blood components, biologics and many refrigerated foods all carry expiry dates that move independently of arrival sequence, which is exactly the condition under which a first in first out rule quietly ships expired-adjacent stock while fresher-dated stock sits behind it.
Short-dated stock needs a rule, not a habit
Short-dated stock, product with only weeks or days of shelf life left, is where a rotation mistake becomes waste rather than a paperwork issue. A vial or unit that expires before it reaches a patient or customer cannot be recovered, and once expired it has to be discarded regardless of how well it was refrigerated the whole time it sat in inventory.
FEFO exists specifically to catch this before it happens: by always moving the nearest-expiry unit first, a warehouse keeps working through its short-dated inventory continuously instead of letting it accumulate behind newer stock nobody is required to touch yet.
Systems that enforce it without relying on memory
Manual FEFO, staff checking dates and physically placing shorter-dated stock at the front of a shelf, works at a small scale but breaks down as inventory volume grows, because it depends on someone remembering to check every unit every time. Barcode and batch-tracked inventory systems remove that dependency by recording each unit's expiry date at receipt and directing pickers to the nearest-expiry unit automatically, regardless of where it physically sits on the shelf.
Cold storage adds a layer most dry warehousing does not face: physically slotting stock to enforce FEFO can conflict with keeping a cold storage warehouse efficient, since the ideal pick location changes constantly as new batches arrive. A system-directed pick list, cross-referenced against temperature data logger records for the same stock, solves this without needing the physical layout to match expiry order at all.
The waste this actually prevents
Every unit that expires unused inside a warehouse or on a shelf is a full loss, not a partial one, and refrigerated products are typically more costly to produce and to store than shelf-stable goods, which makes an expiry-driven write-off in a cold chain more expensive than the same mistake in ordinary retail. FEFO does not reduce how much stock a network holds. It reduces how much of that stock reaches its expiry date without ever being used.
The benefit compounds where shelf life is already short relative to the distribution network's transit time, a vaccine with a year of shelf life moving through several warehouse tiers before reaching a clinic, because every tier that skips FEFO adds delay to product that had little time to spare from the start.
Standard practice across the cold chain
Vaccine cold chains, blood banks, hospital pharmacies, and refrigerated food distributors all run FEFO as standard practice, generally as one requirement inside a broader good distribution or good storage practice program rather than a standalone policy. Warehouse managers and inventory systems enforce it day to day, while quality assurance and regulatory staff check that it is actually being followed rather than just documented.
FEFO does not replace the temperature discipline the rest of the cold chain depends on. A unit correctly rotated by expiry date but held outside its band during storage is still a failed unit, which is why FEFO sits alongside continuous monitoring and logged temperature excursion checks, not in place of them.