How long do peptides last?
It depends on the peptide and its form. Sealed, dry and cold, a lyophilized (freeze-dried) peptide is at its most stable; in solution it degrades faster, at a rate set by sequence, pH, concentration, diluent and temperature. A consensus paper on handling peptides for laboratory assays recommends lyophilized storage at -20 to -80°C beyond six months and concludes that the best conditions depend on the sequence (Hoofnagle et al., 2016).
No single shelf life fits every compound, so the storage text on each product page governs. Disguised Alpha supplies research peptides as lyophilized powders and in some ready-made solutions, sprays and creams, for laboratory research use only. Nothing on this page is guidance for use in people.
Peptide storage temperature by format
Product pages carry a storage card under "Stability information." The wording below is quoted from the cards live on 9 October 2026.
| Format | Temperature | Product page guidance |
|---|---|---|
| Lyophilized powder, as shipped | -20°C | "The most stable form. Store cold and protected from light until it is reconstituted." |
| Reconstituted solution | 2 to 8°C | "Refrigerate once reconstituted and keep it protected from light." The same card lists "Avoid freeze/thaw cycles." |
| Ready-made solution or aerosol spray, unopened | 15 to 25°C | "Room temperature is acceptable before opening. Do not freeze." |
| Ready-made solution, opened | 2 to 8°C | "Refrigerate once the seal is broken and keep it protected from light." |
| Aerosol spray, opened | 2 to 8°C | "Keep the bottle upright, closed and protected from light once opened." |
| Cream | 15 to 25°C | "Store at room temperature with the cap closed, away from direct light and heat." |
Quoted from the BPC-157, TB-500, Tesamorelin, L-Glutathione 200 mg/mL solution, Bacteriostatic Water 0.9%, Semax & Selank Aerosol Spray and ProGlow Cream pages. Some pages word their cards differently.
Why peptides degrade
- Deamidation. Asparagine and glutamine lose their side-chain amide, fastest before glycine. An Asn-Gly hexapeptide deamidated with a half-life of 1.4 days at 37°C and pH 7.4, and swapping the glycine for leucine or proline slowed degradation 33 to 50-fold (Geiger and Clarke, 1987). Across 648 pentapeptide sequences, the slowest half-times reach 2 to 50 years (Robinson et al., 2004).
- Oxidation and light. Cysteine, methionine and tryptophan oxidize, faster at high pH and during freeze-thaw cycles (Hoofnagle et al., 2016). Tryptophan, tyrosine, phenylalanine and cysteine are the residues prone to primary photo-oxidation (Kerwin and Remmele, 2007), which is why the storage cards say to protect from light.
- Hydrolysis and pH. Aspartic acid residues are prone to hydrolysis (Hoofnagle et al., 2016). In accelerated tests at 40 to 80°C, oxytocin degraded fastest at pH 9.0 and slowest at pH 4.5, by deamidation at pH 2.0 and by trisulfide, tetrasulfide and dimer formation from pH 4.5 up (Hawe et al., 2009).
- Aggregation. Sequence, concentration, pH, charge, surfaces, temperature, agitation and lyophilization all shape whether peptides self-associate (Zapadka et al., 2017). In acidic solutions aged at 37°C, glucagon formed fibrils within 24 hours at 2.5 mg/mL or more, while secretin did not aggregate even at 75 mg/mL (Onoue et al., 2004).
- Adsorption. At typical experimental concentrations, 90% or more of three cationic peptides could be lost from solution to the walls of common glass and plastic containers (Kristensen et al., 2015).
Do peptides need to be refrigerated?
Lyophilized peptides go colder than a refrigerator: the product pages list -20°C, a laboratory freezer, for the sealed powder, and 2 to 8°C once it is reconstituted. The dry state slows reactions without stopping them. Deamidation, peptide bond cleavage, oxidation, beta-elimination and aggregation all occur in solids, at rates set by temperature, moisture content, excipients and physical state (Lai and Topp, 1999). Water speeds them up: in lyophilized insulin at 35°C, degradation rose with water content and approached the rate in solution at 20 to 50% water (Strickley and Anderson, 1996).
So the powder stays sealed, cold, dry and dark. Let a cold vial reach room temperature before opening so moisture does not condense on the cake; the consensus paper suggests warming it in a desiccator (Hoofnagle et al., 2016). Reseal and return unused powder to -20°C. The lyophilized peptides guide covers residual moisture.
How long do peptides last at room temperature?
A sealed vial can sit above freezer temperature in transit or on a bench. A dry solid changes more slowly than a solution, but heat and humidity still add up. A lyophilized secretin formulation labeled for -20°C was held at -20°C, 4°C, 25°C, and 25°C with 60% relative humidity for 8 weeks.
The authors reported a 20 to 27% fall in secretin by HPLC by week 8, slower reconstitution, and particles that grew past 2 µm within a week at 25°C and 60% humidity (Srinivasan et al., 2015). Tolerance differs by sequence and formulation, so vials go to -20°C on arrival, and one that sat warm for long is worth checking against its lot certificate.
In solution, degradation climbs with temperature: oxytocin's loss followed the Arrhenius equation (Hawe et al., 2009), and unpreserved water has no defense against microbes introduced on entry (Weck et al., 2005). Reconstituted material leaves 2 to 8°C only while in use.
How long do reconstituted peptides last?
The product pages give a temperature, 2 to 8°C and protected from light, not a day count; the window is compound-specific. These factors set it:
- Sequence. Asn-Gly and aspartic acid sites, oxidizable residues and aggregation-prone stretches shorten it.
- pH and diluent. Bacteriostatic and sterile water carry no buffer, and pH changes stability and solubility, so use the diluent a product page or protocol names. Alteplase, a recombinant protein, kept similar monomer content and activity for 7 days at 37°C in either water, but only the bacteriostatic preparation passed the USP antimicrobial effectiveness test (Weck et al., 2005). See bacteriostatic water vs sterile water.
- Concentration and container. Dilute solutions lose a larger share of peptide to the walls; basic residues bind glass and nonpolar residues bind polypropylene (Hoofnagle et al., 2016). Concentrated solutions of some sequences aggregate sooner (Onoue et al., 2004).
- Handling. Each entry through the stopper risks contamination; each warm-up adds time at a higher temperature.
In practice: reconstitute close to use, label the vial with the date, diluent and concentration, keep it at 2 to 8°C in the dark, and split stock into single-use aliquots. Calculate concentrations from the measured content on the lot's certificate with the peptide reconstitution calculator.
Can you freeze reconstituted peptides?
Not according to the product pages: reconstituted solutions are listed for 2 to 8°C with "Avoid freeze/thaw cycles," and ready-made solutions say "Do not freeze." Freezing is not a neutral pause. Low temperature, freeze-concentration and ice formation are its chief stresses, and freeze-concentration can crystallize buffer components (Bhatnagar et al., 2007).
In a test in the consensus paper, peptide solutions kept 10 days at 4°C, thawed once, or cycled ten times gave similar average signals, but variability was highest after ten cycles, and the authors advise avoiding multiple freeze-thaws (Hoofnagle et al., 2016). Benzyl alcohol, the preservative in bacteriostatic water, worsened freeze-thaw damage to an antibody, and those authors advise keeping reconstituted products at 2 to 8°C, not frozen (Xu et al., 2026). For concentrated calibration stocks, the consensus paper recommends frozen storage in sealed tubes at -70°C or below (Hoofnagle et al., 2016).
How to tell if a peptide has degraded
Look first. A completely dissolved peptide solution is clear, with no flecks or cloudiness (Hoofnagle et al., 2016). Cloudiness, particles or a gel point to aggregation or incomplete dissolution. A powder that now dissolves more slowly or leaves particles has also changed, as in the secretin study (Srinivasan et al., 2015). Some sequences gel in plain water and clear in a suitable diluent, as the tesamorelin gelling guide explains, so cloudiness is not always degradation.
Appearance misses most chemistry: deamidation, oxidation and hydrolysis can leave a solution looking unchanged. They show up as loss of intact peptide by reversed-phase HPLC and as new species by mass spectrometry (Hawe et al., 2009). The reference is the lot's certificate in the COA portal (see What is a COA?), and the Verify Your Product page explains how a lyophilized vial can be tested at an approved independent laboratory. Discard any solution with particles, cloudiness that does not clear, or an unknown history.
Key sources
- Hoofnagle AN, et al. "Recommendations for the Generation, Quantification, Storage, and Handling of Peptides Used for Mass Spectrometry-Based Assays." Clin Chem. 2016. PMID 26719571. DOI 10.1373/clinchem.2015.250563. Consensus recommendations.
- Strickley RG, Anderson BD. "Solid-state stability of human insulin. I. Mechanism and the effect of water on the kinetics of degradation in lyophiles from pH 2-5 solutions." Pharm Res. 1996. PMID 8865303. DOI 10.1023/a:1016043715791. Water in lyophilized powder.
- Srinivasan C, et al. "Stability characterization and appearance of particulates in a lyophilized formulation of a model peptide hormone-human secretin." Int J Pharm. 2015. PMID 25636302. DOI 10.1016/j.ijpharm.2015.01.044. Excursions from -20°C.
- Hawe A, et al. "Towards heat-stable oxytocin formulations: analysis of degradation kinetics and identification of degradation products." Pharm Res. 2009. PMID 19343484. DOI 10.1007/s11095-009-9878-2. pH and temperature.
- Xu ZT, et al. "Benzyl alcohol exacerbates freeze-thaw-induced aggregation of trastuzumab: elucidating mechanisms and formulation implications for clinical practice." Int J Pharm. 2026. PMID 41325828. DOI 10.1016/j.ijpharm.2025.126433. Preservative and freezing.
Frequently asked questions
How long do peptides last in the fridge?
No single figure applies. Reconstituted peptides are listed for 2 to 8°C, and how long they hold there depends on sequence, pH, concentration and diluent, so prepare solutions close to use. Lyophilized powder belongs at -20°C.
How long can you store reconstituted peptides?
As long as the compound stays intact and uncontaminated, which varies by sequence: deamidation half-lives alone run from 1.4 days for an Asn-Gly peptide at 37°C (Geiger and Clarke, 1987) to years for slow sequences (Robinson et al., 2004).
What is the right peptide storage temperature?
-20°C for sealed lyophilized powder, 2 to 8°C after reconstitution, and 15 to 25°C for unopened ready-made formats; the table above has each. Beyond six months, the consensus paper recommends lyophilized storage at -20 to -80°C (Hoofnagle et al., 2016).
Does bacteriostatic water make reconstituted peptides last longer?
It guards against microbes, not chemistry: in the alteplase study, both waters gave similar biochemical stability (Weck et al., 2005), and benzyl alcohol worsened freeze-thaw damage to an antibody (Xu et al., 2026). The bacteriostatic water guide has more.
Is a cloudy peptide solution degraded?
Not always. Cloudiness can mean aggregation or a solubility problem from the diluent or pH; chemical degradation is usually invisible, so HPLC or mass spectrometry is the real check.
Where is the storage information for a specific compound?
On its product page, in the storage card under "Stability information." That text governs over the general guidance here.
Related guides
- What does lyophilized mean?
- Bacteriostatic water for peptides
- Bacteriostatic water vs sterile water
- What is a COA?
- Tesamorelin gelling guide
- Peptide reconstitution calculator
- COA portal: published certificates, by lot
- Peptide solubility
Disguised Alpha products are for research use only. They have not been evaluated for safety or effectiveness in humans. Not for human consumption. All products are intended for laboratory research purposes only.