Medication Storage Calculator
Two clocks start when a vial or pen is first used: the window on its own label, and the window on the preserved diluent it was mixed with. The labelled windows here are read from each product’s own FDA record and the result names it. The diluent field is prefilled at 28 days, CDC’s injection-safety guidance for an opened multi-dose vial — not a figure printed on the bacteriostatic water label itself, which states a preservative but no discard date. Replace it if a manufacturer states another date. There is no third clock for the compound’s own stability, because no research-grade figure has been published that could be cited.
Last reviewed: September 21, 2026
Two clocks start when a vial or pen is first used: the window its own label gives, and the window on the preserved diluent it was mixed with. This adds days to a date; it does not judge whether anything is still good.
Each figure is read from that product’s own FDA label, and the result names the DailyMed record it came from.
Prefilled at 28 days from CDC's injection-safety guidance for healthcare settings, which applies to an opened multi-dose vial. Replace it if your diluent's manufacturer states another date — CDC's own wording defers to the manufacturer.
CDC, Injection Safety — clinical safety considerations: an opened multi-dose vial “should be dated and discarded within 28 days unless the manufacturer states another date for that opened vial.” CDC Injection Safety. This is a limit on the opened container — it says nothing about how long any peptide stays intact in solution, which remains unpublished.
The labelled discard windows this page carries
| Product | Discard window |
|---|---|
| Ozempic pen | 56 days after first use |
| Wegovy pen | 56 days after first use |
| Mounjaro multi-dose vial or KwikPen | 30 days after first use |
| Mounjaro single-dose pen or vial (room temperature) | 21 days after first use |
| Zepbound multi-dose vial or KwikPen | 30 days after first use |
| Zepbound single-dose pen or vial (room temperature) | 21 days after first use |
Each figure is read from that product’s own FDA prescribing information on DailyMed; the calculator’s result names the specific record.
Worked example
An Ozempic pen first used on January 1, 2026 (56-day label window):
| Label discard date | 2026-01-01 + 56 days = 2026-02-26 |
Enter the same date and window into the calculator above and it returns the same date, plus how many days remain (or have passed) counted from today.
Two clocks, and where the diluent figure comes from
A reconstituted product carries two separate discard clocks, both starting at first use: the product’s own labelled window (the table above), and a separate window on the diluent it was mixed with, where the diluent is itself preserved and multi-dose.
The diluent field is prefilled at 28 days, but that figure comes from CDC, not from the bacteriostatic water label itself — which doesn’t print one.
Bacteriostatic Water for Injection, USP (label revised 08/2019) states its preservative — 0.9% or 1.1% benzyl alcohol — and that it’s supplied in a multiple-dose container for repeated withdrawal. Searched in full, the label contains no occurrence of “discard,” “beyond-use,” “puncture,” or “797.” The 28-day figure in the field above comes instead from CDC’s Injection Safety guidance, which states that once a multi-dose vial is opened or accessed, it “should be dated and discarded within 28 days unless the manufacturer states another date for that opened vial.”
That is a limit on the CONTAINER, stated for healthcare settings handling any opened multi-dose vial — not a bacteriostatic-water-specific figure, and not a claim about how long a reconstituted peptide stays chemically stable in solution. USP <797>, a separate pharmacy-compounding standard sometimes cited for the same 28-day figure, remains behind a paywall Prof. Peptide has not opened to confirm against this specific product. The field is editable — replace the prefilled figure if a manufacturer states a different discard date, and the calculator adds it to the date of first use the same way it does the label window.
No third clock for the compound’s own stability
A reconstituted research-grade peptide’s own stability in solution — separate from either the product’s labelled window or the diluent’s — is not modelled here, because no published research-grade stability figure exists for Prof. Peptide to cite. Sourced storage-duration claims of this kind were removed from 52 places on the site for exactly this reason; a figure added here would be the same defect a 53rd time. This calculator states two clocks because two clocks have sources; it does not state a third to make the picture feel complete.
FAQ
medication storage calculator discard date
How long is Ozempic good for after opening?
How long can Mounjaro be used after first use?
Does bacteriostatic water expire 28 days after opening?
How long does reconstituted peptide stay stable?
For a compound’s own reconstitution and dosing arithmetic, see the general peptide dosage calculator.