Add four things at the moment a vial is first opened: the date opened, the discard date (28 days later by convention), the initials of the person who opened it and, if the vial will be separated from its box, the lot number. The manufacturer’s printed label is never covered, written over or removed. Secondary information goes on a small flag label around the neck, a strip of laboratory tape, or the box.
What the printed label already carries
Product name, composition (0.9% benzyl alcohol), nominal volume, lot number, expiration date, storage conditions and the manufacturer’s name. Every one of these has to stay legible for the life of the vial, because they are what tie the vial to its certificate of analysis. See lot numbers and traceability.
A simple convention
| Field | Example | Why |
|---|---|---|
| Opened | 2026-09-28 | Starts the in-use clock. |
| Discard | 2026-10-26 | 28 days after opening; the vial is discarded on this date even if liquid remains. The discard-date calculator works it out. |
| Initials | AB | Identifies who opened it for the reagent log. |
| Lot | (copied from the printed label) | Only needed when the vial leaves its labeled box. |
Where to put it
- A flag label folded around the neck of the vial, below the cap, leaves the printed label fully visible.
- Laboratory tape on the shoulder of the vial works for 10 mL and 30 mL vials; 3 mL vials have little free surface, so the box or a flag label is used instead.
- Use a permanent, solvent-resistant marker. Never write on the flip-off cap: it is removed at first opening and discarded.
- Use one date format across the laboratory (ISO 8601, year-month-day, avoids the day/month ambiguity of numeric dates).
Unopened stock
Unopened vials need no extra labeling. The box is marked with the date received and shelved so that the earliest expiration date is used first. See running a stockroom supply and the SOP template, which includes a reagent log format.
Related
Shelf life after opening · How to store bacteriostatic water
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