Once a vial or pen is opened or reconstituted, a separate "beyond-use" clock starts — often much shorter than the printed expiration date. Pick your product type and opening date to see the discard date, sourced from FDA labeling or USP compounding standards.
Discard date calculator
A one-off calculation — nothing here is saved or sent anywhere.
How to Use This Calculator
Two inputs — the rest comes from published storage guidance for that product type.
Pick your product typeChoose the closest match — FDA-approved products (semaglutide/tirzepatide pens, testosterone vials) have specific labeled windows; other reconstituted peptides use the general USP compounding-standard default.
Enter your opening dateThe date you first punctured the vial, first used the pen, or reconstituted the powder.
Read your discard dateAlong with the source of that guidance and any product-specific caveats worth knowing.
Set a reminderBeyond-use dates are frequently missed simply because nobody wrote them down — mark your calendar or set a phone reminder for the calculated date.
Where These Numbers Come From
Real published FDA labeling where a product is FDA-approved; the general USP compounding-standard default everywhere else — never an invented number.
Semaglutide pen (Ozempic/Wegovy). 56 days after first use, whether stored refrigerated or at room temperature (59–86°F). FDA prescribing information, Ozempic and Wegovy labels.
Tirzepatide pen/vial (Mounjaro/Zepbound). 21 days at room temperature (up to 86°F) for the single-dose pen/vial — the most common consumer product. Some multi-dose KwikPen variants allow up to 30 days; check your specific product's label. FDA prescribing information, Mounjaro and Zepbound labels.
Testosterone cypionate/enanthate multi-dose vial. 28 days after first puncture is the standard CDC/USP default for a multi-dose vial. Some manufacturer labels differ — Pfizer's Depo-Testosterone label states no specific post-opening limit beyond the printed expiration date, while some generic manufacturers specify up to 56 days. Check your specific product insert. CDC injection safety guidance; USP General Chapter <797>; manufacturer package inserts vary.
Other reconstituted peptide (bacteriostatic water). 28 days is the general USP <797> default beyond-use date for a multi-dose container after first puncture. This is a general compounding-safety standard, not a stability study specific to any one research peptide — most research peptides have no independently published reconstituted-stability data at all. USP General Chapter <797>, multi-dose container default.
Other reconstituted peptide (plain, non-bacteriostatic sterile water). Without a preservative, USP <797> treats this as a same-day-use preparation — refrigerated storage allows roughly 24 hours before any unused portion should be discarded. This is a major reason bacteriostatic water (which contains benzyl alcohol as a preservative) is preferred for multi-use vials. USP General Chapter <797>.
Estimate only — not medical advice. These are general reference windows from FDA labeling and USP compounding standards — not a stability study of your specific product, storage conditions, or handling history. Temperature excursions (heat, freezing, direct sunlight) can shorten actual safe-use time regardless of the calendar date. For any FDA-approved product, always defer to your specific product's package insert; for research peptides, treat the reconstituted-peptide default as a conservative estimate, not a guarantee, and discard immediately if you notice cloudiness, discoloration, or particles.
Frequently Asked Questions
What's the difference between an expiration date and a beyond-use/discard date?
The printed expiration date applies to an unopened, sealed product stored correctly. Once a vial is punctured or a powder is reconstituted, a separate — usually much shorter — "beyond-use date" (BUD) applies, based on contamination and stability risk after the seal is broken, regardless of how much time is left before the original expiration date.
Why is the beyond-use date so much shorter than the expiration date?
Once a rubber stopper is punctured, each puncture creates a small entry point, and sterility can no longer be fully guaranteed indefinitely — this is a contamination-risk concern, separate from whether the drug itself has chemically degraded.
Why does testosterone cypionate have varying discard windows across sources?
Manufacturer labels genuinely differ — some specify no additional limit beyond the printed expiration date, others specify up to 56 days, and 28 days is the conservative USP/CDC default many pharmacies apply when a manufacturer doesn't specify otherwise. Check your specific product's package insert for the definitive answer.
Is it safe to use a vial or pen slightly past its calculated discard date if it looks fine?
Appearance isn't a reliable indicator — a solution can lose potency or develop unsafe contamination without any visible change. The safest approach is to follow the calculated discard date rather than relying on how the product looks or smells.
Why don't most research peptides have a specific published storage window?
Because they aren't FDA-approved products, there's no requirement for the manufacturer to conduct and publish formal stability studies the way there is for an approved drug. The 28-day USP default used here is a general sterile-compounding safety standard, not evidence that a specific peptide is chemically stable for exactly that long.
Does freezing extend a vial's usable life?
No — for testosterone specifically, freezing is explicitly not recommended (it can cause crystallization), and for most other injectables, freezing is not a validated storage method unless specifically stated on the label. Never use a product that has been frozen unless its label explicitly permits it.
What should I do if I don't know my exact reconstitution or opening date?
If you're unsure, the safest approach is to assume the vial is closer to its discard date than you'd like and either verify with whoever prepared it, or treat it conservatively and discard if there's any doubt.
Does this calculator save my dates anywhere?
No — everything runs locally in your browser. To get automatic reminders ahead of a discard date for your actual inventory, see the full Peptide Plug app.
Related Tools
More free calculators for tracking peptide and hormone protocols.