Storage
The clock starts when you add water.
A freeze-dried vial is stable for a long time. A reconstituted one is not, and the date you mixed it is the single thing nobody writes down.
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The science
Two different expiry dates
01
The date printed on the box applies to the sealed, lyophilised powder. Freeze-dried peptide is stable for a long period because there is no water for degradation reactions to occur in. That date stops being the relevant one the moment you reconstitute.
02
Once water is added, a new and much shorter clock starts. Bacteriostatic water contains a preservative that inhibits bacterial growth, which is what permits a vial to be entered repeatedly, and commonly supports around 28 days refrigerated. Plain sterile water has no preservative and a far shorter window.
03
Degradation is gradual rather than sudden. A vial does not become dangerous overnight at day 29, but potency falls over time in solution, so a dose drawn late in the window may deliver less than you intend. Contamination risk also rises with each entry into the vial.
04
Refrigerate, never freeze. Ice crystal formation can damage peptide structure, so the fridge rather than the freezer is the right place once a vial is mixed. Keeping it out of light and returning it promptly after each draw both help.
FAQ
Common questions
How long does reconstituted peptide last in the fridge?
Bacteriostatic water commonly allows around 28 days refrigerated. Sterile water has no preservative and a much shorter window. Manufacturer guidance for a specific compound takes precedence over any general figure.
Can I freeze a reconstituted vial?
Freezing is generally not recommended, as ice crystal formation can damage the molecule. Refrigerate instead, and keep the vial out of light.
What happens if I use an expired vial?
Peptides degrade over time in solution, so potency falls and you may be taking less than you think. Contamination risk also rises with each entry into the vial.
Does the expiry date on the box apply after mixing?
No. The printed date applies to the sealed freeze-dried powder. Once water is added a new and much shorter clock starts.
How should I record the mix date?
Write it directly on the vial. Everything else in a protocol can be recalculated from the numbers, but a forgotten reconstitution date cannot be recovered.
Can I extend the shelf life?
Not meaningfully. Consistent refrigeration and minimising the number of entries help the vial reach its expected window, but nothing extends it beyond that. If you routinely have product left over, a smaller vial is the better answer.
VialClock
This page calculates. Your notes app forgets.
Every tool here is stateless by design. What it cannot do is remember that your vial was mixed eleven days ago, or that a step-up is due this week.
Browse all calculatorsThis tool performs arithmetic on figures you enter, or presents a manufacturer-published schedule. It does not know your protocol, will never suggest a dose, and is not medical advice. Dosing decisions belong with a qualified prescriber.