How long do reconstituted peptides last?

How long do peptides last once reconstituted?

Research peptides have no tested shelf life once mixed. Nobody has published the answer for them. A 2023 review says the shelf life of peptides in solution is very limited, and much shorter than in freeze-dried (lyophilized) form².

The only tested numbers come from approved peptide products, and they show how far apart the answers can be:

Both EGRIFTA products contain the same peptide, yet one must be used at once and the other lasts a week. The difference comes from the formula and the liquid used. That's why one product's number can't be borrowed for another.

Where does the 28-day rule for peptide vials come from?

It comes from CDC and USP guidance for multi-dose vials: once opened, a vial is dated and thrown away within 28 days unless the maker states a different date^6–7. It's a limit on contamination risk after the stopper has been pierced, not a test of the peptide.

• USP, which writes US pharmacy standards, defines multi-dose containers as ones that have passed antimicrobial effectiveness testing⁷. A peptide you mix at home hasn't had that test.
• USP also says the 28-day limit is separate from a vial's beyond-use date. Its example is a multi-dose vial with a 60-day date that must still be thrown away 28 days after first puncture⁷.
• Bacteriostatic water is itself a multi-dose vial, preserved with 0.9% benzyl alcohol⁸. So the opened bac water bottle also gets a 28-day date⁶.

Pharmacies are held to short default dates too. When there is no stability data for a sterile preparation, USP says its maximum dates must not be exceeded⁷. One example in USP's FAQs: preparations once called "low-risk" now get 4 days at room temperature or 10 days in the fridge⁷.

So 28 days is the outside limit for an opened multi-dose vial. It is not evidence that a research peptide is still at full strength on day 28.

Do reconstituted peptides need to be refrigerated?

Most reconstituted peptides are kept in the fridge at 2-8 °C (36-46 °F), but not all. A 2023 review notes that most peptide drugs need low-temperature storage, and that peptide injections in liquid form are often kept cold and protected from light³. Light can trigger oxidation in some peptides³.

The exceptions are why the label matters:

• EGRIFTA WR says not to refrigerate after mixing. It stays at room temperature for its 7 days⁵.
• EGRIFTA SV says not to store, refrigerate or freeze it once mixed⁴.
• Freezing is not a way to make a mixed peptide last longer. Freezing, heating and agitation can make peptides clump together³, and every GLP-1 label in the table below says not to use the medicine if it has been frozen^9–12.

For a research peptide with no label, the fridge, away from light, is the general practice described in the literature³. Keep it in its box or wrapped, and away from the freezer compartment.

How long do Ozempic, Wegovy, Mounjaro and Zepbound last out of the fridge?

Ozempic and Wegovy multi-dose pens last 56 days after first use. Wegovy single-dose pens can be out of the fridge for up to 28 days, and Mounjaro or Zepbound single-dose pens and vials for up to 21 days in total. Each limit comes from the product's US label^9–12.

Left your GLP-1 pen or peptide vial out overnight?

A GLP-1 pen left out overnight at normal room temperature is usually still within its label's room-temperature allowance. Each product has its own rule, listed below from its US label. If your situation isn't covered, ask your pharmacist.

• Mounjaro or Zepbound single-dose pen or vial: the night counts toward a total of 21 days out of the fridge, as long as it stayed at or below 30 °C (86 °F)^11–12.
• Mounjaro or Zepbound KwikPen or multi-dose vial: once in use it can be kept in the fridge or at room temperature up to 30 °C, for 30 days after first use^11–12.
• Wegovy single-dose pen or Ozempic single-dose syringe: each can be kept at 8-30 °C for up to 28 days^9–10.
• Ozempic or Wegovy FlexTouch pen already in use: it can be kept at 15-30 °C for the 56 days after first use^9–10.
• Unused Ozempic or Wegovy FlexTouch pen: the labels say to keep it in the fridge before first use and don't give an allowance for time out^9–10. Ask your pharmacist or the manufacturer.
• Hotter than 30 °C (86 °F), or frozen: this is outside every label above. Don't use a pen that has been frozen^9–12.
• A research peptide vial: there is no label to check, so there is no tested answer.

How long do compounded semaglutide or tirzepatide vials last?

A compounded semaglutide or tirzepatide vial lasts until the beyond-use date on the pharmacy label, or 28 days after you first pierce it, whichever comes first. That's the USP rule for multiple-dose compounded preparations⁷.

Store it the way the pharmacy label says. The storage rules for Ozempic, Wegovy, Mounjaro and Zepbound apply to those branded products, not to compounded vials.

How long can peptides be stored before mixing?

Unmixed, freeze-dried (lyophilized) peptides keep much longer than mixed ones. A 2023 review says most stay stable for several years at -20 °C when protected from light². That's a general finding, not a promise for any one product.

Approved products set their own rules. Both EGRIFTA vials are kept at room temperature, 20-25 °C, in the box to protect them from light before mixing^4–5. Always go by the label or the expiry date when there is one. For more on mixing, see how to reconstitute peptides.