How long do reconstituted peptides last?

There’s no single answer: how long a mixed vial lasts depends on the product, the liquid it was mixed with and how it’s stored, and FDA-approved labels range from “use immediately” to about a month. Use the discard or beyond-use date on your manufacturer’s or pharmacy’s label; if your vial has no such date, there’s no validated number to fall back on, so ask the pharmacist who dispensed it. The peptide calculator shows how many doses a mixed vial holds, so you can see whether it will be used up in time.

What real labels say

These are FDA-approved products that are mixed from a powder. Look at how much the answer varies:

Sources: the Glucagon, Serostim, Egrifta WR and Novarel labels.

Two lessons stand out. The diluent matters: the same drug, Serostim, goes from “use now” to two weeks depending on whether a preservative is present. And the storage temperature matters too: Egrifta WR is kept at room temperature after mixing, while others must be refrigerated. You can’t carry one product’s numbers over to another.

Two clocks: the water and the vial

If you mix from a multi-dose bottle of bacteriostatic water, you’re tracking two dates:

1. The water bottle. Once punctured, a multi-dose vial is dated and discarded within 28 days unless the manufacturer says otherwise (CDC, citing USP General Chapter 797).
2. The mixed vial. Its own date comes from the drug’s label or your pharmacy.

Use each one until its own date, and never past the expiry printed on either.

Compounded and unlabeled vials

Compounded drugs are not FDA-approved, and the FDA doesn’t review their safety, quality or effectiveness before they’re sold (FDA). They should come with a beyond-use date (BUD), which the FDA describes as “a date beyond which a compounded drug product should not be used” (FDA guidance). That date, on your pharmacy label, is the one to follow.

Products with no label at all, such as vials sold as “research” peptides, come with no tested stability data for use at home. Peptides are only marginally stable in water, which is why so many are sold as freeze-dried powder (Izutsu, 2018), and in liquid form they often degrade chemically (Angkawinitwong et al., 2015). Any “lasts X weeks” figure you read online for these products is a guess, not data.

When to throw a vial away early

Discard a vial before its date if:

• the liquid turns cloudy or discolored, or has particles in it (labels including Egrifta WR and Serostim say not to use it if so);
• it has been frozen when the label says not to freeze;
• it has been left out of the fridge longer than its label allows;
• the stopper was touched or contaminated, or you’re not sure.

A clear liquid isn’t proof the drug is still potent or sterile. It’s just the minimum check.

Will the vial run out before its date?

This is simple math, and worth doing before you mix. The numbers below are for illustration only and are not a dose.

A 10 mg vial with a prescribed amount of 0.5 mg contains 10 ÷ 0.5 = 20 doses. If those doses are a week apart and the label says discard 30 days after first use, you’ll use about 5 of them. The other 15 will be thrown away.

The same logic appears on a multi-dose GLP-1 label: Zepbound’s multi-dose vial is discarded 30 days after first use or after 4 weekly doses, “even if there is medicine left in it” (Zepbound label). The reconstitution calculator shows doses per vial so you can compare that number with your discard date.

Common mistakes

• Using one product’s shelf life for another. Labels differ by drug, strength and diluent.
• Counting from the wrong day. The clock starts when you mix or first puncture the vial, not when you bought it.
• Not writing the mix date on the vial.
• Freezing a mixed vial to “make it last”. Egrifta WR and Serostim labels say not to freeze reconstituted vials.

Questions people ask