How Long Does Compounded Tirzepatide Last in the Fridge? A Microdoser's Vial Math

A compounded tirzepatide or semaglutide vial lasts only until the beyond-use date the pharmacy prints on its label. Once a multi-dose vial has been punctured, the US sterile-compounding standard caps use at that date or 28 days, whichever comes first ¹. Brand Zepbound is different: its four-dose KwikPen is discarded 30 days after first use ².

The fridge keeps the drug cold. It does not reset the clock. And at a microdose, the clock is usually what runs out first, long before the vial is empty.

What does the date on my vial mean?

Compounded injectables made by a state-licensed pharmacy fall under USP General Chapter <797>, the standard for sterile compounding. Its definition is blunt: the beyond-use date (BUD) "is the date, or the hour and date, after which the CSP must not be used" ¹. CSP means compounded sterile preparation, which is what your vial is.

Two limits stack on a multi-dose vial. The first is the BUD the pharmacy assigns. The second starts when you first push a needle through the stopper. USP's own FAQ quotes the chapter: "After a multiple-dose CSP is initially entered or punctured, the multiple-dose CSP must not be used for longer than the assigned BUD or 28 days, whichever is shorter" ¹. USP gives its own example of the difference: a multiple-dose vial can carry a 60-day BUD and still have to be discarded 28 days after its first puncture ¹.

So 28 days is a ceiling, not a typical figure. Your label may give fewer days, and the label is what counts. If the label's date has passed, the preparation "must not be used and must be discarded," in USP's words, even when doses are scheduled after it ¹.

One caveat on where your vial came from. USP says the chapter's quality standards were written for 503A pharmacies and "are not intended for outsourcing facilities or pharmaceutical manufacturers" ¹. A vial from a 503B outsourcing facility is dated under that facility's own testing. Follow its label and in-use instructions, and ask the pharmacy if the label gives an expiration date but says nothing about how long the vial lasts once opened.

Brand storage rules, for comparison

Brand pens and vials carry tested storage limits in their prescribing information. These do not transfer to a compounded product, which has a different formula and was never tested the same way. They are useful as a sense of scale.

Lilly's multi-dose Zepbound presentations are the closest brand analogue to a compounded vial, and their rule is strict: throw the KwikPen or multi-dose vial away "after a total of 30 days at room temperature, 30 days after first use, or after taking 4 weekly doses, even if there is medicine left in it" ². Each holds exactly four weekly doses, so a full-dose user finishes it inside the window. That is the design a microdoser's vial lacks.

Microdose vial math: doses in the vial vs days allowed

Here is the problem in one table. Take a 10 mg vial and the 28-day ceiling, the most generous outcome a punctured multi-dose vial can have under USP. Four weekly doses fit inside 28 days.

At a full 2.5 mg weekly dose, the vial and the date line up. At 0.25 mg, you use one milligram out of ten before the vial has to go. The rest is not savings waiting in the fridge. It is drug you paid for and cannot use. We work through the cost side of that in what microdosing GLP-1 really costs, and the vial-waste calculator runs it on your own vial size, dose and label date.

Three things actually shrink the waste: a smaller vial, a lower concentration that suits a small dose, or a provider whose price falls when the milligrams do. Using the vial past its date is not on the list. The reconstitution guide covers how concentration and volume change what a small dose looks like in the syringe, and which providers price by dose covers the third.

Left out, frozen or traveling: what to do

Left out of the fridge. Brand labels allow set periods at room temperature, up to 86°F: 21 days for a Zepbound single-dose pen or vial, 28 days for a Wegovy single-dose pen before the cap comes off ^2,3. No equivalent figure exists for a compounded vial unless your pharmacy prints one. If a compounded vial sat out overnight, call the dispensing pharmacy and ask before you use it.

Frozen. Every brand label here says the same thing in different words. Zepbound: "Do not use ZEPBOUND if frozen." Wegovy: throw the pen away if it "has been frozen." Ozempic: "do not use OZEMPIC if it has been frozen" ^2,3,4. The Ozempic label also says not to store the pen "directly adjacent to the refrigerator cooling element," which is good advice for any vial ⁴.

Flying. TSA lets you carry "medically necessary liquids, medications and creams in excess of 3.4 ounces or 100 milliliters" in your carry-on, screened separately from the rest of your bag, and recommends clear labels ⁵. Gel ice packs for medically necessary items are allowed "regardless of their physical state," frozen or slushy, if you tell the officer ⁶. Keep the pharmacy label on the vial; it is also the only record of its BUD.

Signs a vial has gone bad

Zepbound's instructions give the brand checklist: before injecting, make sure the medicine is not frozen, is not cloudy, is colorless to slightly yellow and has no particles in it ². A compounded preparation may not look the same as the brand, so ask your pharmacy what yours should look like on day one. Any change from that, cloudiness, particles, discoloration, or a cracked or loose stopper, is a reason not to inject it.

The date matters more than the look. A vial that still looks perfect on day 29 after first puncture is past its limit under USP's rule. Contamination does not show, and a compounded product's safety record is the reason the limit exists.