How to store peptides

Lyophilised peptides keep longest sealed, dry and dark in a freezer at -20°C or colder, with a fridge at 2 to 8°C for short-term use. Bachem, the UK's NIBSC (part of the MHRA) and Sigma-Aldrich all publish storage guidance for research peptides. They agree on direction and differ on the exact numbers.

We built the table from each guide's own wording. ^[1][2][3] ICH Q1A(R2), the international stability guideline for medicines, defines refrigerated storage as 5°C ± 3°C and freezer storage as -20°C ± 5°C. ^[8] Hold your fridge and freezer to those bands.

Moisture comes next. Peptides tend to be hygroscopic, so Bachem advises letting the container reach room temperature in a desiccator before you open it. Absorbed water reduces peptide content and may decrease stability. ^[1] A 1994 study found lyophilised insulin aggregated faster as temperature and water content rose, and the extent of aggregation tracked the powder's water uptake. ^[9]

Light and air finish the list. NIBSC advises storage away from bright light. ^[2] In a 2003 study, lyophilised bovine growth hormone degraded under near-UV light between 305 and 410 nm, starting at tryptophan. ^[10] Sigma-Aldrich notes that sequences containing C, M or W are prone to air oxidation and suggests replacing the air in the vial with nitrogen or argon. ^[3] Keep vials in their box or an opaque case, capped tight.

Lyophilised peptides degrade slowly at room temperature, and peptides in solution degrade much faster. NIBSC states that dry peptides are stable at room temperature for days to weeks, with -20°C preferred for the long term. ^[2] Bachem notes that peptides may be shipped at room temperature. ^[1] A sealed vial that spends a few mild days in transit sits inside what these guides describe.

Solutions are a different case, because water lets the chemistry run. A 1987 study found that a model hexapeptide containing the Asn-Gly pair lost its side-chain amide with a half-life of only 1.4 days at 37°C and pH 7.4. ^[11] That pair is the fast extreme. Swapping the glycine for a bulky leucine or proline slowed degradation 33 to 50-fold.

Heat is where "unrefrigerated" turns into damage. In a 2005 study of a dark sedan parked on 16 clear days, the cabin rose about 22°C (40°F) above outside air on average, and 80% of the rise came in the first 30 minutes. Even the coolest day, about 22°C outside, reached about 47°C inside. Cracking the windows made no significant difference. ^[12]

Finished medicines show how narrow the allowances are. The manufacturer's tirzepatide may be kept at room temperature for up to 21 days and should not go back in the fridge afterwards. ^[13] That figure comes from stability testing of one formulated product. No equivalent figure is published for research vials.

Reconstituted peptides belong in the fridge at 2 to 8°C, in a labelled vial, away from light. Bachem advises against keeping peptides in solution for long, because they slowly degrade even in sterile, oxygen-free solution. ^[1] NIBSC recommends sterile buffers at around pH 5 to 6 to extend the life of a solution. ^[2]

Label every vial with the compound, batch number, solvent, concentration and date of first puncture. For opened vials of a preserved, multi-use product, the CDC's rule is to date them and discard them within 28 days unless the manufacturer states another date. It also notes that a preservative does not give complete protection against bacterial contamination. ^[14]

Keep the stock concentrated. NIBSC warns that peptides in solution adsorb to vial surfaces, and at high dilution a large percentage can be lost that way. ^[2] Dilute on the day you need a lower concentration.

The drying step can leave its own mark. A 2016 study of teriparatide, the 34-residue parathyroid hormone fragment, found its lyophilised formulations stable for months. After reconstitution, some samples precipitated within two to four weeks, more so at higher concentration and temperature, while samples never lyophilised showed no precipitation for 12 weeks. ^[15] Our guide on reconstituting peptides covers solvents and the concentration maths, and BAC Water in 3ml vials is the preserved solvent we stock at A$8.

A reconstituted peptide lasts days to a few weeks in the fridge depending on its sequence, and no published figure exists for most research peptides. These are the limits the primary sources do state.

The fridge itself is the weak link. In a 2019 study, 338 people placed temperature sensors beside insulin in their home fridges and bags. Refrigerated insulin sat outside its recommended range 11.3% of the time, about 2 hours 43 minutes a day, and 17% of sensors recorded temperatures below 0°C. ^[4] Clinic fridges do no better by default. On the NSW Central Coast, 31% of 102 general practice vaccine fridges held 2 to 8°C and 36% fell below 0°C. ^[16]

Put a min-max thermometer beside the vials and read it daily. Keep vials in the body of the fridge, clear of the cooling plate, where freezing is least likely.

Repeated freezing and thawing can damage peptides, and the lab guides say to avoid it. NIBSC calls repeated freeze-thaw deleterious to peptides and says to avoid frost-free freezers, which swing widely in temperature during frequent automatic defrosting. ^[2] Sigma-Aldrich says to avoid it for powders and solutions alike and to freeze individual aliquots. ^[3] Split a stock into single-use portions so each one thaws once.

The measured evidence is more mixed than the warnings. In plasma frozen at -20°C and thawed up to four times, most of 15 hormones showed no change, although ACTH fell slightly. ^[17] In another plasma study, up to three thaw-refreeze rounds did not significantly affect GLP-1 or glucagon. Freezing itself cut glucagon recovery by almost 50% against immediate analysis. ^[18] The first freeze can matter more than the later thaws.

The solvent changes the answer. A 2026 study of the antibody trastuzumab found that benzyl alcohol worsened freeze-thaw aggregation, partly through extra ice-water interfaces. The authors advise against frozen storage of benzyl alcohol-containing biologics and recommend keeping reconstituted product at 2 to 8°C. ^[5] BAC Water contains 0.9% benzyl alcohol. The study used an antibody, and we found no equivalent study of short peptides. Our working rule: keep BAC Water solutions in the fridge, and freeze aliquots only when the peptide is dissolved in plain sterile water or buffer.

Peptides containing asparagine (N), glutamine (Q), cysteine (C), methionine (M) or tryptophan (W) are the most storage-sensitive, and Bachem, NIBSC and Sigma-Aldrich each flag the same five residues. ^[1][2][3] Asparagine deamidates. ^[11] Cysteine, methionine and tryptophan are prone to air oxidation. ^[3]

We checked the published sequence of every compound we stock against those five residues. Of our 28 research compounds, 25 have a verified amino acid sequence. Seven contain none of the five and 18 contain at least one.

Use the table as triage. A residue's neighbours change its rate a great deal: in the 1987 study, a leucine or proline after asparagine slowed degradation 33 to 50-fold against glycine. ^[11] Compounds in the lower rows earn the coldest storage, the fewest thaws and a dark case. BPC-157 contains none of the five, which is a sequence observation with no measured shelf life behind it. The other three compounds (hCG, NAD+ and 5-Amino-1MQ) have no verified sequence in our data; NAD+ is a coenzyme and 5-Amino-1MQ is a small molecule.

Peptides should travel cold, dark and padded: solutions in an insulated cooler with ice packs, and sealed vials in a case kept out of direct heat. Ordinary post does not control temperature. In a 2023 US study, 36 packages carrying data loggers spent an average of 68.3% of transit time outside the 20 to 25°C range of USP chapter 659, with extremes of about -15°C and 39°C. ^[19] In summer, next-business-day parcels spent 13.6% of transit outside that range against 43.1% for 3-day parcels.

The car is the other hazard. The sedan study above reached about 47°C inside on a 22°C day within the hour. ^[12] Carry vials with you, and keep the cooler out of the boot and out of the sun.

For a solution, wrap the vial so it never touches a frozen pack, because the home-fridge data show how easily vials drop below 0°C. ^[4] Move it to the fridge on arrival. Our Travel Cooler Bag costs A$29.95, the Hard Shell Cooler Bag is sold with 2 ice packs for A$28, and the 9-vial Travel Storage Case holds a set of sealed vials together for A$18.

You can see some degradation, such as haze, particles, gel or a wet, collapsed cake, but most chemical degradation is invisible and needs HPLC and mass spectrometry to detect. NIBSC notes that a solution that has gelled, stays hazy or carries a surface scum has probably not dissolved and is only finely suspended. ^[2] In the teriparatide study, visible precipitation tracked a rise in subvisible particles, which no eye can see. ^[15]

Moisture also lowers net peptide content, and Bachem lists storage conditions and humidity exposure among the factors that change it. ^[20] A dry-looking cake can still hold less peptide than the label suggests.

A certificate is a snapshot of one batch on its test date. Every batch we sell is tested by an independent lab before sale for purity by HPLC and identity by mass spectrometry, and the report sits in our certificate of analysis library under the batch number on the vial. Our testing page explains the process, and the guide on how to read a peptide certificate of analysis shows where extra peaks and mass shifts appear. Storage decides whether the vial in your fridge still matches that report.

Freezing, dissolving or repacking a peptide leaves its legal status unchanged, because Poisons Standard entries name substances. BPC-157 is the worked example. The June 2026 instrument, in force from 1 June 2026, lists it in Schedule 4 (prescription only) and in Appendix D clause 5, which makes possession without authority an offence. ^[21] WADA's 2026 Prohibited List, effective 1 January 2026, names BPC-157 in class S0, prohibited at all times. ^[22]

The Poisons Standard also has a storage clause of its own. A Schedule 3 or Schedule 4 poison stored at premises for supply to the public must be kept in a part of the premises the public cannot access. ^[21] Status differs by compound, and our guide to Australian peptide law sets out each schedule.

Cold, dry, dark and thawed once covers most of peptide storage: -20°C or colder for sealed powder, 2 to 8°C for solutions, and a dated vial discarded within 28 days of first puncture. Check the fridge with a thermometer, keep BAC Water solutions out of the freezer and give sequences containing N, Q, C, M or W the most care. The batch certificate records what left the lab, and storage decides whether the vial still matches it.