How to Store Peptides: Complete Guide (2026)

Lyophilized peptides are freeze-dried into a powder or cake. The removal of water makes them remarkably stable. Unopened lyophilized vials stored at -20°C can retain full potency for three to five years.

At refrigerator temperature (2-8°C), expect one to two years of stability. At room temperature (20-25°C), stability drops to three to six months, depending on the specific peptide.

Key rules for powder storage:

• Keep vials sealed until ready to reconstitute
• Store away from light (UV breaks down certain amino acids, especially tryptophan)
• Avoid humidity (moisture initiates degradation even in powder form)
• Do not store in the fridge door (temperature fluctuates every time you open it)
• A desiccant packet in the storage container adds an extra layer of protection

Once you add bacteriostatic water to a lyophilized peptide, the clock starts. Refrigerate immediately at 2-8°C and use the vial within 30 days.

Bacteriostatic water contains 0.9% benzyl alcohol, which inhibits microbial growth. This is why reconstituted peptides last longer with bacteriostatic water (28-30 days) than with sterile water (5-7 days). If you reconstituted with plain sterile water, use the vial within one week.

Never freeze a reconstituted peptide. Water expands when it freezes, forming ice crystals that physically shear peptide bonds. The result: a cloudy, degraded solution with reduced or zero potency. This is the single most common storage mistake.

For reconstitution instructions, see our step-by-step reconstitution guide. Use our reconstitution calculator to get exact measurements.

Best for long-term storage of lyophilized peptides. At -20°C, deamidation and oxidation rates drop to near zero. Most peptides retain 95%+ potency for three to five years at this temperature.

A standard kitchen freezer works fine. You do not need a laboratory-grade deep freezer at -80°C, though it would extend shelf life even further.

One caution: do not repeatedly remove a vial from the freezer to check on it. Each freeze-thaw cycle introduces condensation, and moisture is the enemy. Take out only what you plan to reconstitute.

The standard storage temperature for both lyophilized and reconstituted peptides. All reconstituted peptides must be stored here. Lyophilized peptides remain stable for one to two years.

Where in the fridge matters. The back of the middle shelf maintains the most consistent temperature. The door is the worst location: temperature swings 5-10°C every time you open it. The vegetable crisper is acceptable if it stays within range.

Keep peptide vials in a small container or zip-lock bag to protect them from accidental spills and light exposure. If your fridge has a bright interior LED, consider wrapping vials in aluminum foil.

Acceptable only for short-term storage of lyophilized peptides (under three months) or during shipping. Reconstituted peptides should never be stored at room temperature for more than a few hours.

At 25°C, deamidation rates increase significantly. Peptides containing asparagine-glycine (Asn-Gly) sequences are most vulnerable, as this motif degrades fastest at elevated temperatures.

If you receive a peptide shipment at room temperature, this is normal. Lyophilized peptides tolerate days of room-temperature shipping without meaningful potency loss. Refrigerate or freeze upon arrival.

UV radiation degrades tryptophan and tyrosine residues. Peptides containing these amino acids (most growth hormone secretagogues, melanocortin peptides) lose potency faster under light exposure.

Practical steps:

• Store vials in the original box or wrap in aluminum foil
• Keep away from windows and direct sunlight
• Use amber vials for reconstituted peptides if available
• Add a silica gel desiccant packet to your storage container

Humidity is the second threat. Lyophilized peptides absorb moisture from the air, which initiates hydrolysis. Keep vials sealed. If you open a vial to reconstitute it, do not leave it open on the counter while you prepare your syringe. Work efficiently: open, reconstitute, close, refrigerate.

Always use bacteriostatic water (BAC water) for reconstitution. The 0.9% benzyl alcohol acts as a preservative, preventing bacterial growth and extending shelf life from days to weeks.

If you accidentally reconstituted with sterile water, use the entire vial within one week. Draw all doses into separate insulin syringes and store the pre-loaded syringes in the fridge. This avoids repeated needle punctures into a preservative-free vial.

1. 1.Swirl gently. Never shake a peptide vial. Shaking creates foam and can physically damage peptide chains through shear stress. Swirl or roll between your palms until the powder dissolves completely.

1. 1.Inspect the solution. It should be clear and colorless. If you see particles, cloudiness, or color, something went wrong. Do not inject a cloudy solution.

1. 1.Label the vial. Write the date of reconstitution, the peptide name, and the concentration (mg/mL) directly on the vial with a fine-tip marker.

1. 1.Refrigerate within 5 minutes. Do not leave a reconstituted vial on the counter while you prepare your injection site. Draw your dose, then refrigerate immediately.

1. 1.Store upright. Keep the vial upright (stopper facing up) to minimize the surface area of liquid in contact with the rubber stopper. Some stoppers leach trace amounts of silicone or rubber compounds over time.

1. 1.Use a clean needle every draw. Never reuse a needle to draw from a vial. Each puncture introduces potential contaminants and enlarges the hole in the stopper.

No. Freezing a reconstituted peptide destroys it. Ice crystals form during freezing, and these crystals physically break peptide bonds. When thawed, the peptide is partially or fully degraded.

This applies to all reconstituted peptides without exception. Semaglutide pens, BPC-157 vials, TB-500 solutions: none survive freezing intact.

If you have more reconstituted peptide than you can use in 30 days, you over-reconstituted. Next time, use less bacteriostatic water or reconstitute only the vials you need. Use our reconstitution calculator to plan exact volumes.

Lyophilized (powder) peptides left at room temperature:

Reconstituted peptides left at room temperature:

Reconstituted peptides degrade much faster because water enables hydrolysis. Bacterial growth is also a concern once the vial warms above 8°C, even with bacteriostatic water.

Discard the vial if:

• Reconstituted peptide was left out for more than 24 hours
• The solution has turned cloudy, yellow, or contains visible particles
• The vial has an unusual smell
• You are unsure how long it was left out (when in doubt, discard)

Still usable if:

• Lyophilized powder was left at room temperature for under a month
• Reconstituted peptide was left out for under 4 hours and solution is still clear
• The vial was in an insulated bag during a short power outage (check temperature)

A peptide that has lost 10% potency still works. You will need a slightly higher dose to compensate, or you may notice slightly slower results. A peptide that has been contaminated with bacteria is dangerous. When the question is potency loss versus safety risk, always err on the side of discarding.

Check every vial before each use:

• Cloudiness. A reconstituted peptide should be perfectly clear, like water. Any haziness indicates aggregation (peptide chains clumping together) or bacterial contamination. Discard.
• Particles. Floating specks, fibers, or sediment mean the peptide has precipitated out of solution. Discard.
• Color change. Most peptide solutions are colorless. A yellow or brown tint indicates oxidation. Discard.
• Foaming. Excessive foam that does not settle suggests protein denaturation. This can happen if the vial was shaken vigorously.
• Rubber fragments. Small black or gray pieces from the stopper can fall into the vial after repeated needle punctures. Discard if visible.

For lyophilized peptides, the powder should be a white to off-white cake or fluffy powder. A yellow or brown powder indicates degradation before you even reconstitute it.

Sometimes a peptide looks fine but has lost significant potency. Watch for these indicators:

• Reduced effectiveness. A BPC-157 protocol that was working for two weeks suddenly stops producing results. The vial may have degraded.
• Slower onset. Results take noticeably longer than expected based on published timelines. Compare with our dosage chart.
• Injection site reactions. Increased redness, swelling, or pain at the injection site that was not present with a fresh vial. This can indicate bacterial contamination or degradation byproducts.
• No response at proven doses. If you have used a peptide before and know your effective dose, and a new vial produces no response at the same dose, the product is likely degraded or counterfeit.

Track your results. Keep a simple log of dose, date, and subjective response. This makes it much easier to spot a degraded vial versus natural variation in results.

The TSA permits medically necessary liquids, gels, and aerosols in carry-on baggage in quantities exceeding the standard 3.4 oz (100 mL) limit. Peptide vials, bacteriostatic water, and syringes fall under this exemption when they are for personal medical use.

Practical tips:

• Carry peptides in your carry-on bag (not checked luggage, which is not temperature controlled)
• Pack vials, syringes, and BAC water together in a clear zip-lock bag
• No prescription label is required by the TSA, but having one avoids questions
• Declare the items at the security checkpoint if asked
• Insulin syringes are specifically permitted; they do not need to be in original packaging

The TSA screens millions of passengers carrying injectable medications daily. Peptide vials attract less attention than you expect.

International travel adds complexity. Each country has its own rules on importing pharmaceuticals, research chemicals, and controlled substances.

General guidelines:

• Carry a prescription or letter from your doctor if possible, even if the peptide is not prescription-only in your country. This provides cover in ambiguous situations.
• Research the destination country's rules. Some countries classify certain peptides (particularly GLP-1 agonists like semaglutide) as prescription-only medications. Carrying them without a prescription may be illegal.
• Keep peptides in original packaging with labels showing the peptide name, purity, and quantity.
• Declare at customs if required. Undeclared medications can be confiscated.

For longer trips (two weeks or more), bring lyophilized vials and bacteriostatic water separately. Reconstitute at your destination. This simplifies temperature management and extends the usable window.

Reconstituted peptides need to stay between 2-8°C. Lyophilized peptides are more forgiving but still benefit from cool storage. Here is what works:

For short trips (under 8 hours): - A small insulated lunch bag with one or two gel ice packs keeps the interior below 8°C for 4-8 hours. - Wrap vials in a paper towel to prevent direct contact with ice packs. Direct contact can freeze the peptide.

For longer trips (8-24 hours): - Use a hard-sided insulated medical cooler. These are designed for insulin and maintain temperature for 12-24 hours. - Add two to three gel packs. Check the internal temperature with a small thermometer.

For extended travel (multi-day): - Bring lyophilized (powder) vials instead of reconstituted ones. Powder tolerates room temperature for days. - Reconstitute upon arrival using a travel-size vial of bacteriostatic water. - If you must bring reconstituted peptides, request a mini-fridge at your hotel.

Never use dry ice. Dry ice (-78°C) will freeze and destroy reconstituted peptides. It is also restricted on most airlines.

Each time a lyophilized peptide is removed from the freezer and returned, condensation forms inside the vial. This moisture initiates degradation.

The solution: do not store all your vials in one bag that you open repeatedly. Separate them. Take out only the vial you intend to reconstitute. If you bought a bulk supply, divide it into individual bags.

For reconstituted peptides, even a single freeze event (accidental or intentional) causes irreversible damage. If your fridge thermostat malfunctions and the back of the fridge hits 0°C, check your vials. Partial freezing still creates ice crystals.

The fridge door is the warmest and most variable zone. Every time you open the door, the temperature swings by 5-10°C. Over weeks, these micro-fluctuations accelerate degradation.

Move peptide vials to the back of the middle shelf, where the temperature is coldest and most stable. This alone can extend reconstituted peptide life by several days.

Some users store vials on a countertop or desk between injections. Even indirect sunlight through a window degrades light-sensitive amino acids. MOTS-c and peptides containing tryptophan are particularly vulnerable.

The fix is simple: store vials in the fridge or, at minimum, in a dark drawer or cabinet. If you use a vial at a desk, return it to the fridge immediately after drawing your dose.

Some users reconstitute their entire supply to save time. This is false economy. You now have multiple vials of liquid with a 30-day clock ticking, instead of stable powder that lasts years.

Reconstitute one vial at a time. When it is nearly empty, reconstitute the next. Use our peptide cost calculator to plan your supply so you buy the right amount of bacteriostatic water.

Shaking creates air bubbles, foam, and mechanical shear stress on the peptide chains. This can cause aggregation and denaturation, particularly with larger peptides like TB-500 (43 amino acids) and Thymosin Alpha-1 (28 amino acids).

Swirl gently. Roll the vial between your palms. Let gravity and time do the work. If the powder does not dissolve after two to three minutes of gentle swirling, let the vial sit in the fridge for 30 minutes and try again.