Store peptides as a dry powder for as long as possible: tightly closed, cool and in the dark. For longer-term storage of powder, peptide manufacturers recommend −20 °C or colder [1][2]. Before opening a cold vial, let it warm to room temperature with the cap still on. Dissolved peptides are much less stable: divide them into portions, keep them cold and avoid repeated freezing and thawing. If the label gives storage advice, that takes precedence.
Powder or solution: the biggest difference
In water, peptides can undergo various changes. The chain can break (hydrolysis), side chains can oxidise or deamidate, and molecules can clump together [3]. These reactions require water or proceed much faster in water. A freeze-dried powder (lyophilisate) is therefore the best form in which to keep peptides in stock. Bachem advises against storing peptide solutions for long periods [2]. So only dissolve what you need in the near future.
Temperature: fridge or freezer
| Form | Short term | Long term |
|---|---|---|
| Dry powder, closed | Fridge (2–8 °C) or as stated on the label | −20 °C or colder [1][2] |
| Solution | Fridge, as a general guideline for up to about a week [1] | Frozen in portions: −20 °C for one to two weeks, −80 °C for longer [1] |
Powder can safely be kept at room temperature for short periods: according to Bachem, freeze-dried peptides can be shipped at room temperature [2]. That is not the same as leaving them on a shelf for months. Our products carry storage advice on the label and the product page, and it can differ between products: bacteriostatic water, for example, is stored at room temperature.
Moisture: the underestimated factor
Many peptides are hygroscopic: they attract water from the air. This lowers the peptide content per milligram and can reduce stability [2]. A study of freeze-dried insulin showed how large this effect can be: the more water the powder absorbed, the more it aggregated [4].
The most important habit that follows from this is to take a vial out of the fridge or freezer and let it warm to room temperature with the cap on, ideally in a desiccator, before opening it [1][2]. If you open it while it is still cold, moisture from the air condenses directly onto the powder. Reseal the vial immediately after use. A practical tip: keep vials in the fridge in a closed container with a sachet of desiccant (silica gel), which absorbs the moisture that gets in every time the fridge door is opened.
Light and oxygen
Keep peptides out of bright light [1]. Light can cause oxidation, particularly of the amino acid tryptophan [3]. Peptides containing cysteine (C), methionine (M) or tryptophan (W) are also sensitive to oxidation by oxygen. Sigma-Aldrich recommends replacing the air in the vial with nitrogen or argon for peptides that contain cysteine [1]. Trace metals such as iron and copper can also accelerate oxidation in solution [3]. So use clean glassware and pure water, and do not leave dissolved peptides in contact with metal parts for longer than necessary.
Which peptides are particularly sensitive
The amino acid sequence tells you a lot. Peptides containing asparagine (N), glutamine (Q), cysteine (C), methionine (M) or tryptophan (W) are less stable in solution and have a more limited shelf life [1][2]. Asparagine and glutamine can deamidate; cysteine, methionine and tryptophan can oxidise [3]. If your peptide contains one or more of these amino acids, keep its time in solution as short as possible.
Dissolved peptides: portions and freeze-thawing
If you need to store a solution, divide it immediately into single-use portions (aliquots). That way, you do not have to freeze and thaw your stock repeatedly; repeated freezing and thawing is harmful to both powder and solution [1]. Sigma-Aldrich also notes that sterile buffers with a pH of 5 to 6 extend the storage life, and that solutions with a pH above 8 should be stored frozen when not in use [1]. Which solvent is suitable depends on the peptide; more on this in What is bacteriostatic water.
Label and record
Stability starts with knowing what you have. For each vial, note the product name, the batch number, the date of receipt, the date of opening or dissolving, the solvent and the volume. Monitor the fridge or freezer temperature with a min–max thermometer. That way, if a result looks unusual, you can check whether storage played a part and compare your records with the certificate of analysis (COA).
The full range is available in the shop; questions about shipping are answered in the FAQ.
Further reading
- How to read a certificate of analysis (COA): HPLC and MS explained
- What is bacteriostatic water and what is it used for in the lab?
- How to store retatrutide: temperature, light and shelf life
- Retatrutide pen or vial: what are the differences?
- Knowledge base: peptides and research materials explained
Sources
- Sigma-Aldrich (Merck). Handling and Storage Guidelines for Peptides and Proteins. sigmaaldrich.com (accessed 30 September 2026)
- Bachem. Handling and Storage Guidelines for Peptides. bachem.com (accessed 30 September 2026)
- Nugrahadi PP, Hinrichs WLJ, Frijlink HW, et al. Designing Formulation Strategies for Enhanced Stability of Therapeutic Peptides in Aqueous Solutions: A Review. Pharmaceutics 2023;15(3):935. doi:10.3390/pharmaceutics15030935
- Costantino HR, Langer R, Klibanov AM. Moisture-induced aggregation of lyophilized insulin. Pharmaceutical Research 1994;11(1):21–29. doi:10.1023/a:1018981208076
For laboratory research use only. Clean Peptides products are not intended for use in humans or animals. This article provides general information and is not medical advice.
