Shelf life and expiry dating
Last updated: 11 September 2026
Two different periods are often conflated: how long a sealed pen lasts, and how long it lasts once you start using it. They are set by different things and neither is a guess.
Sealed shelf life
A sealed pen has a stated expiry date derived from stability data for that formulation held at its specified storage temperature. It is a property of the product and the storage conditions together — a date assumes the cold chain was maintained, and it does not describe a pen that has spent time outside its range.
In-use life is shorter and starts at first use
Once a pen is first punctured it becomes an in-use product, as a reconstituted vial does from the moment it is mixed. The relevant period is then how long the solution remains suitable under the storage conditions you are actually giving it, which is invariably shorter than the sealed date and is counted from first use rather than from manufacture.
This is the number people most often miss, because the printed expiry date is the visible one and the in-use period is not printed on the pen.
What an expiry date does not tell you
It does not certify the current contents. A date is a prediction made at manufacture under assumed conditions; the batch certificate is the record of what was actually measured in that lot at the time of testing. The two answer different questions and neither substitutes for the other.
It also does not survive a temperature excursion. If a parcel has been warm for an extended period (an excursion in transit) the printed date no longer describes the product, which is why arrival condition matters more than the date on the label.
Frequently asked questions
How long does a sealed pen last?
Until its stated expiry date, provided it has been stored at the specified temperature throughout. The date assumes the cold chain was maintained.
Does the expiry date apply once I start using it?
No. In-use life is a separate, shorter period counted from first use, and it depends on the storage conditions the pen is actually kept in.
Is the expiry date a guarantee of content?
No. It is a stability prediction made at manufacture. The batch certificate records what was measured in that specific lot.
This page is educational and intended for research and informational use only. It is not medical advice, a treatment recommendation, or dosing guidance, and it makes no claims about outcomes. Body Pharm EU supplies research-grade materials for laboratory use. These statements have not been evaluated by the EMA.